Samarium
Encyclopedia
Samarium is a chemical element
with the symbol Sm, atomic number
62 and atomic weight
150.36. It is a moderately hard silvery metal
which readily oxidizes in air. Being a typical member of the lanthanide
series, samarium usually assumes the oxidation state
+3. Compounds of samarium(II) are also known, most notably monoxide
SmO, monochalcogenides
SmS, SmSe and SmTe, as well as samarium(II) iodide
. The last compound is a common reducing agent
in chemical synthesis
. Samarium has no significant biological role and is only slightly toxic.
Samarium was discovered in 1879 by the French chemist Paul Émile Lecoq de Boisbaudran
and named after the mineral samarskite
from which it was isolated. The mineral itself was earlier named after a Russian mine official, Colonel Vasili Samarsky-Bykhovets
, who thereby became the first person to have a chemical element named after him, albeit indirectly. Although classified as a rare earth element
, samarium is the 40th most abundant element in the Earth's crust and is more common than such metals as tin
. Samarium occurs with concentration up to 2.8% in several minerals including cerite
, gadolinite
, samarskite
, monazite
and bastnäsite
, the last two being the most common commercial sources of the element. These minerals are mostly found in China
, the USA, Brazil
, India
, Sri Lanka
and Australia
; China is by far the world leader in samarium mining and production.
The major commercial application of samarium is in samarium-cobalt magnet
s which have permanent magnetization
second only to neodymium magnet
s; however, samarium compounds can withstand significantly higher temperatures, above 700 °C, without losing their magnetic properties. Radioactive isotope
samarium-153
is the major component of the drug samarium (153Sm) lexidronam (Quadramet) which kills cancer cells in the treatment of lung cancer
, prostate cancer
, breast cancer
and osteosarcoma
. Another isotope, samarium-149, is a strong neutron
absorber and is therefore added to the control rod
s of nuclear reactor
s. It is also formed as a decay product during the reactor operation and is one of the important factors considered in the reactor design and operation. Other applications of samarium include catalysis
of chemical reaction
s, radioactive dating
and an X-ray laser
.
having the hardness and density similar to those of zinc
. With the boiling point of 1794 °C, samarium is the third most volatile lanthanide after ytterbium
and europium
; this property facilitates separation of samarium from the mineral ore. At ambient conditions, samarium normally assumes a trigonal structure (α form). Upon heating to 731 °C, its crystal symmetry changes into hexagonal close-packed
(hcp), however the transition temperature depends on the metal purity. Further heating to 922 °C transforms the metal into a body-centered cubic
(bcc) phase. Heating to 300 °C combined with compression to 40 kbar
results in a double-hexagonal close-packed structure (dhcp). Applying higher pressure of the order of hundreds or thousands of kilobars induces a series of phase transformations, in particular with a tetragonal
phase appearing at about 900 kbar. In one study, the dhcp phase could be produced without compression, using a nonequilibrium annealing regime with a rapid temperature change between about 400 and 700 °C, confirming the transient character of this samarium phase. Also, thin films of samarium obtained by vapor deposition may contain the hcp or dhcp phases at ambient conditions.
Samarium (and its sesquioxide
) are paramagnetic
at room temperature. Their corresponding effective magnetic moments, below 2µB, are the 3rd lowest among the lanthanides (and their oxides) after lanthanum and lutetium. The metal transforms to an antiferromagnetic
state upon cooling to 14.8 K. Individual samarium atoms can be isolated by encapsulating them into fullerene
molecules. They can also be doped between the C60 molecules in the fullerene
solid, rendering it superconductive
at temperatures below 8 K. Samarium doping of iron-based superconductor
s – the most recent class of high-temperature superconductors – allows to enhance their transition temperature to 56 K, which is the highest value achieved so far in this series.
. Even when stored under mineral oil
, samarium gradually oxidizes and develops a grayish-yellow powder of the oxide
-hydroxide
mixture at the surface. The metallic appearance of a sample can be preserved by sealing it under an inert gas such as argon
.
Samarium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form samarium hydroxide:
Samarium dissolves readily in dilute sulfuric acid
to form solutions containing the yellow to pale green Sm(III) ions, which exist as [Sm(OH2)9]3+ complexes:
Samarium is one of the few lanthanides that exhibit the oxidation state +2. The Sm2+ ions are blood-red in solutions.
Sm2O3. As many other samarium compounds, it exists in several crystalline phases. The trigonal form is obtained by slow cooling from the melt. The melting point of Sm2O3 is rather high (2345 °C) and therefore melting is usually achieved not by direct heating, but with induction heating
, through a radio-frequency coil. The Sm2O3 crystals of monoclinic symmetry can be grown by the flame fusion method (Verneuil process
) from the Sm2O3 powder, that yields cylindrical boules up to several centimeters long and about one centimeter in diameter. The boules are transparent when pure and defect-free and are orange otherwise. Heating the metastable trigonal Sm2O3 to 1900 °C converts it to the more stable monoclinic phase. Cubic Sm2O3 has also been described.
Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm2O3 with samarium metal at elevated temperature (1000 °C) and pressure above 50 kbar; lowering the pressure resulted in an incomplete reaction. SmO has the cubic rock-salt lattice structure.
, selenide
and telluride
. Divalent chalcogenides SmS, SmSe and SmTe with cubic rock-salt crystal structure are also known. They are remarkable by converting from semiconducting to metallic state at room temperature upon application of pressure. Whereas the transition is continuous and occurs at about 20–30 kbar in SmSe and SmTe, it is abrupt in SmS and requires only 6.5 kbar. This effect results in spectacular color change in SmS from black to golden yellow when its crystals of films are scratched or polished. The transition does not change lattice symmetry, but there is a sharp decrease (~15%) in the crystal volume. It shows hysteresis, that is when the pressure is released, SmS returns to the semiconducting state at much lower pressure of about 0.4 kbar.
Their further reduction with samarium, lithium or sodium metals at elevated temperatures (about 700–900 °C) yields dihalides. The diiodide can also be prepared by heating SmI3, or by reacting the metal with 1,2-diiodoethane in anhydrous tetrahydrofuran
at room temperature:
In addition to dihalides, the reduction also produces numerous non-stoichiometric
samarium halides with a well-defined crystal structure, such as Sm3F7, Sm14F33, Sm27F64, Sm11Br24, Sm5Br11 and Sm6Br13
As reflected in the table above, samarium halides change their crystal structures when one type of halide atoms is substituted for another, which is an uncommon behavior for most elements (e. g. actinides). Many halides have two major crystal phases for one composition, one being significantly more stable and another being metastable. The latter is formed upon compression or heating, followed by quenching to ambient conditions. For example, compressing the usual monoclinic samarium diiodide and releasing the pressure results in a PbCl2-type orthorhombic structure (density 5.90 g/cm3), and similar treatment results in a new phase of samarium triiodide (density 5.97 g/cm3).
powders of samarium oxide and boron, in vacuum, yields a powder containing several samarium boride phases, and their volume ratio can be controlled through the mixing proportion. The powder can be converted into larger crystals of a certain samarium boride using arc melting
or zone melting
techniques, relying on the different melting/crystallization temperature of SmB6 (2580 °C), SmB4 (about 2300 °C) and SmB66 (2150 °C). All these materials are hard, brittle, dark-gray solids with the hardness increasing with the boron content. Samarium diboride is too volatile to be produced with these methods and requires high pressure (about 65 kbar) and low temperatures between 1140 and 1240 °C to stabilize its growth. Increasing the temperature results in the preferential formations of SmB6.
Samarium hexaboride is a typical intermediate-valence compound where samarium is present both as Sm2+ and Sm3+ ions at the ratio 3:7. It belongs to a class of Kondo insulator
s, that is at high temperatures (above 50 K), its properties are typical of a Kondo metal, with metallic electrical conductivity characterized by strong electron scattering, whereas at low temperatures, it behaves as a non-magnetic insulator with a narrow band gap
of about 4–14 meV. The cooling-induced metal-insulator transition in SmB6 is accompanied by a sharp increase in the thermal conductivity
, peaking at about 15 K. The reason for this increase is that electrons themselves do not contribute to the thermal conductivity at low temperatures, which is dominated by phonon
s, but the decrease in electron concentration reduced the rate of electron-phonon scattering.
s are prepared by melting a graphite-metal mixture in an inert atmosphere. After the synthesis, they are unstable in air and are studied also under inert atmosphere. Samarium monophosphide SmP is a semiconductor
with the bandgap of 1.10 eV, the same as in silicon
, and high electrical conductivity of n-type
. It can be prepared by annealing at 1100 °C an evacuated quartz ampoule containing mixed powders of phosphorus and samarium. Phosphorus is highly volatile at high temperatures and may explode, thus the heating rate has to be kept well below 1 °C/min. Similar procedure is adopted for the monarsenide SmAs, but the synthesis temperature is higher at 1800 °C.
A large number of crystalline binary compounds are known for samarium and one of the group-4, 5 or 6 element X, where X is Si, Ge, Sn, Pb, Sb or Te, and metallic alloys of samarium form another large group. They are all prepared by annealing mixed powders of the corresponding elements. Many of the resulting compounds are non-stoichiometric and have nominal compositions SmaXb, where the b/a ratio varies between 0.5 and 3.
Sm(C5H5)3 and its chloroderivatives Sm(C5H5)2Cl and Sm(C5H5)Cl2. They are prepared by reacting samarium trichloride with NaC5H5 in tetrahydrofuran
. Contrary to cyclopentadienides of most other lanthanides, in Sm(C5H5)3 some C5H5 rings bridge each other by forming ring vertexes η1 or edges η2 toward another neighboring samarium atom, thereby creating polymeric chains. The chloroderivative Sm(C5H5)2Cl has a dimer structure which is more accurately expressed as (η5-C5H5)2Sm(µ-Cl)2(η5-C5H5)2. There, the chlorine bridges can be replaced, for instance, by iodine, hydrogen or nitrogen atoms or by CN groups.
The (C5H5)– ion in samarium cyclopentadienides can be replaced by the indenide (C9H7)– or cyclooctatetraenide
(C8H8)2– ring, resulting in Sm(C9H7)3 or KSm(η8-C8H8)2. The latter compound has a similar structure to that of uranocene
. There is also a cyclopentadienide of divalent samarium, Sm(C5H5)2 – a solid which sublimates at about 85 °C. Contrary to ferrocene
, the C5H5 rings in Sm(C5H5)2 are not parallel but are tilted by 40°.
Alkyls and aryl
s of samarium are obtained through a metathesis reaction in tetrahydrofuran or ether
:
Here R is a hydrocarbon group and Me stands for methyl.
of 128 Bq
/g. It is composed of four stable isotope
s: 144Sm, 150Sm, 152Sm and 154Sm, and three extremely long-lived radioisotopes, 147Sm (half-life t½ = 1.06 years), 148Sm (7 years) and 149Sm (>2 years), with 152Sm being the most abundant (natural abundance
26.75%). 149Sm is listed by various sources either as stable or radioactive isotope.
The long-lived isotopes,146Sm, 147Sm, and 148Sm, primarily decay by emission of alpha particles
to isotopes of neodymium
. Lighter unstable isotopes of samarium primarily decay by electron capture
to isotopes of promethium
, while heavier ones convert through beta decay
to isotopes of europium
.
The alpha-decay of 147Sm to 143Nd with a half-life
of 1.06 years serve for samarium-neodymium dating
The half-lives of 151Sm and 145Sm are 90 years and 340 days, respectively. All of the remaining radioisotopes have half-lives that are less than 2 days, and the majority of these have half-lives that are less than 48 seconds. Samarium also has five nuclear isomer
s with the most stable being 141mSm (half-life
22.6 minutes), 143m1Sm (t½ = 66 seconds) and 139mSm (t½ = 10.7 seconds).
Detection of samarium and related elements was announced by several scientists in the second half of the 19th century; however, most sources give the priority to the French
chemist Paul Émile Lecoq de Boisbaudran
. Boisbaudran isolated samarium oxide and/or hydroxide in Paris
in 1879 from the mineral samarskite
((Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16) and identified a new element in it via sharp optical absorption lines. The Swiss chemist Marc Delafontaine
announced a new element decipium
(from meaning "deceptive, misleading") in 1878, but later in 1880–1881 demonstrated that it was a mixture of several elements, one being identical to the Boisbaudran's samarium. Although samarskite was first found in the remote Russian region of Urals, by the late 1870s its deposits had been located in other places making the mineral available to many researchers. In particular, it was found that the samarium isolated by Boisbaudran was also impure and contained comparable amount of europium
. The pure element was produced only in 1901 by Eugène-Anatole Demarçay.
Boisbaudran named his element samaria after the mineral samarskite, which in turn honored Vasili Samarsky-Bykhovets
(1803–1870). Samarsky-Bykhovets was the Chief of Staff of the Russia
n Corps of Mining Engineers who granted access for the German mineralogists, brothers Gustav Rose
and Heinrich Rose
, to study the mineral samples from the Urals. In this sense samarium was the first chemical element to be named after a person. Later the name samaria used by Boisbaudran was transformed into samarium, to conform with other element names, and samaria nowadays is sometimes used to refer to samarium oxide, by analogy with yttria, zirconia, alumina, ceria, holmia, etc. The symbol Sm was suggested for samarium; however an alternative Sa was frequently used instead until the 1920s.
Prior to the advent of ion-exchange separation technology in the 1950s, samarium had no commercial uses in pure form. However, a by-product of the fractional crystallization purification of neodymium was a mixture of samarium and gadolinium that acquired the name of "Lindsay Mix" after the company that made it. This material is thought to have been used for nuclear control rod
s in some of the early nuclear reactors. Nowadays, a similar commodity product has the name "samarium-europium-gadolinium
" (SEG) concentrate. It is prepared by solvent extraction from the mixed lanthanide
s isolated from bastnäsite (or monazite). Since the heavier lanthanides have the greater affinity for the solvent used, they are easily extracted from the bulk using relatively small proportions of solvent. Not all rare earth producers who process bastnäsite do so on large enough scale to continue onward with the separation of the components of SEG, which typically makes up only one or two percent of the original ore. Such producers will therefore be making SEG with a view to marketing it to the specialized processors. In this manner, the valuable europium content of the ore is rescued for use in phosphor
manufacture. Samarium purification follows the removal of the europium. Currently, being in oversupply, samarium oxide is less expensive on a commercial scale than its relative abundance in the ore might suggest.
With the average concentration of about 8 parts per million (ppm), samarium is the 40th most abundant element in the Earth's crust. It is the fifth most abundant lanthanide and is more common than such element as tin. Samarium concentration in soils varies between 2 and 23 ppm, and oceans contain about 0.5–0.8 parts per trillion. Distribution of samarium in soils strongly depends on its chemical state and is very inhomogeneous: in sandy soils, samarium concentration is about 200 times higher at the surface of soil particles than in the water trapped between them, and this ratio can exceed 1,000 in clays.
Samarium is not found free in nature, but, like other rare earth elements, is contained in many minerals, including monazite
, bastnäsite
, cerite
, gadolinite
and samarskite
; monazite (in which samarium occurs at concentrations of up to 2.8%) and bastnäsite are mostly used as commercial sources. World resources of samarium are estimated at two million tonne
s; they are mostly located in China, US, Brazil, India, Sri Lanka and Australia, and the annual production is about 700 tonnes. Country production reports are usually given for all rare-earth metals combined. By far, China has the largest production with 120,000 tonnes mined per year; it is followed by the US (about 5,000 tonnes) and India (2,700 tonnes). Samarium is usually sold as oxide, which at the price of about 30 USD/kg is one of the cheapest lanthanide oxides. Whereas mischmetal
– a mixture of rare earth metals containing about 1% of samarium – has long been used, relatively pure samarium has been isolated only recently, through ion exchange
processes, solvent extraction techniques, and electrochemical deposition. The metal is often prepared by electrolysis of a molten mixture of samarium(III) chloride
with sodium chloride
or calcium chloride
. Samarium can also be obtained by reducing its oxide with lanthanum
. The product is then distilled to separate samarium (boiling point 1794 °C) and lanthanum (b. p. 3464 °C).
Samarium-151 is produced in nuclear fission
of uranium
with the yield of about
0.4% of the total number of fission events. It is also synthesized upon neutron capture
by samarium-149, which is added to the control rod
s of nuclear reactors. Consequently, samarium-151 is present in spent nuclear fuel
and radioactive waste.
One of the most important applications of samarium is in samarium-cobalt magnet
s, which have a nominal composition of SmCo5 or Sm2Co17. They have high permanent magnetization, which is about 10,000 times that of iron and is second only to that of neodymium magnet
s. However, samarium-based magnets have higher resistance to demagnetization, as they are stable to temperatures above 700 °C (cf. 300–400 °C for neodymium magnets). These magnets are found in small motors, headphones, high-end magnetic pickups for guitars and related musical instruments. For example, they are used in the motors of a solar-powered
electric aircraft Solar Challenger
and in the Samarium Cobalt Noiseless
electric guitar and bass pickups.
Another important application of samarium and its compounds is as catalyst and chemical reagent. Samarium catalysts assist decomposition of plastics, dechlorination of pollutants such as polychlorinated biphenyl
s (PCBs), as well as the dehydration and dehydrogenation
of ethanol. Samarium(III) triflate (Sm(OTf)3, that is Sm(CF3SO3)3) is one of the most efficient Lewis acid
catalysts for a halogen-promoted Friedel–Crafts reaction with alkenes. Samarium(II) iodide
is a very common reducing and coupling agent in organic synthesis
, for example in the desulfonylation reactions
; annulation
; Danishefsky
, Kuwajima
, Mukaiyama
and Holton Taxol total syntheses
; strychnine total synthesis
; Barbier reaction
and other reductions with samarium(II) iodide
.
In its usual oxidized form, samarium is added to ceramics and glasses where it increases absorption of infrared light. As a (minor) part of mischmetal
, samarium is found in "flint
" ignition device of many lighter
s and torches.
Radioactive samarium-153 is a beta emitter with a half-life of 46.3 hours. It is used to kill cancer cells in the treatment of lung cancer
, prostate cancer
, breast cancer
and osteosarcoma
. For this purpose, samarium-153 is chelated
with ethylene diamine tetramethylene phosphonate (EDTMP
) and injected intravenously. The chelation prevents accumulation of radioactive samarium in the body that would result in excessive irradiation and generation of new cancer cells. The corresponding drug has several names including samarium (153Sm) lexidronam and its trade name is Quadramet.
Samarium-149 has high cross-section for neutron capture
(41,000 barns
) and is therefore used in the control rods of nuclear reactor
s. Its advantage compared to competing materials, such as boron and cadmium, is stability of absorption – most of the fusion and decay products of samarium-149 are other isotopes of samarium which are also good neutron absorbers. For example, the cross sections of samarium-151 is 15,000 barns, it is on the order of hundred barns for samarium-150, 152, 153, and is 6,800 barns for natural (mixed-isotope) samarium. Among the decay products in a nuclear reactor, samarium-149 is regarded as the second most important for the reactor design and operation after xenon-135
.
crystals were used as an active medium in one of the first solid-state laser
s designed and constructed by Peter Sorokin
(co-inventor of the dye laser
) and Mirek Stevenson at IBM
research labs in early 1961. This samarium laser emitted pulses of red light at 708.5 nm. It had to be cooled by liquid helium and thus did not find practical applications.
Another samarium-based laser became the first saturated X-ray laser
operating at wavelengths shorter than 10 nanometers. It provided 50-picosecond pulses at 7.3 and 6.8 nm suitable for applications in holography
, high-resolution microscopy
of biological specimens, deflectometry, interferometry
and radiography
of dense plasmas related to confinement fusion and astrophysics
. Saturated operation meant that the maximum possible power was extracted from the lasing medium, resulting in the high peak energy of 0.3 mJ. The active medium was samarium plasma produced by irradiating samarium-coated glass with a pulsed infrared Nd-glass laser
(wavelength ~1.05 µm).
The change in electrical resistivity in samarium monochalcogenides
can be used in a pressure sensor or in a memory device triggered between a low-resistance and high-resistance state by external pressure, and such devices are being developed commercially. Samarium monosulfide also generates electric voltage upon moderate heating to about 150 °C that can be applied in thermoelectric power converters.
The analysis of relative concentrations of samarium and neodymium isotopes 147Sm, 144Nd and 143Nd allows the determination of the age and origin of rocks and meteorites in samarium-neodymium dating
. Both elements are lanthanides and have very similar physical and chemical properties. Therefore, Sm-Nd dating is either insensitive to partitioning of the marker elements during various geological processes, or such partitioning can well be understood and modeled from the ionic radii
of the involved elements.
When ingested, only about 0.05% of samarium salts is absorbed into the bloodstream and the remainder is excreted. From the blood, about 45% goes to the liver and 45% is deposited on the surface of the bones where it remains for about 10 years; the balance 10% is excreted.
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
with the symbol Sm, atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
62 and atomic weight
Atomic weight
Atomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...
150.36. It is a moderately hard silvery metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
which readily oxidizes in air. Being a typical member of the lanthanide
Lanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
series, samarium usually assumes the oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
+3. Compounds of samarium(II) are also known, most notably monoxide
Monoxide
A monoxide is any oxide containing just one atom of oxygen in the molecule. For example, Potassium oxide , has only one atom of oxygen, and is thus a monoxide. Water is also a monoxide; see dihydrogen monoxide hoax. A well known monoxide is carbon monoxide ; see carbon monoxide poisoning....
SmO, monochalcogenides
Samarium monochalcogenides
Samarium monochalcogenides are chemical compounds with the composition SmX, where Sm stands for the lanthanide element samarium and X denotes any one of three chalcogen elements, sulfur, selenium or tellurium, resulting in the compounds SmS, SmSe or SmTe...
SmS, SmSe and SmTe, as well as samarium(II) iodide
Samarium(II) iodide
Samarium iodide is a green solid composed of samarium and iodine, with a melting point of 520 °C where the samarium atom has a coordination number of seven in a capped octahedral configuration...
. The last compound is a common reducing agent
Reducing agent
A reducing agent is the element or compound in a reduction-oxidation reaction that donates an electron to another species; however, since the reducer loses an electron we say it is "oxidized"...
in chemical synthesis
Chemical synthesis
In chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions...
. Samarium has no significant biological role and is only slightly toxic.
Samarium was discovered in 1879 by the French chemist Paul Émile Lecoq de Boisbaudran
Paul Emile Lecoq de Boisbaudran
Paul Émile Lecoq de Boisbaudran was a French chemist known for his discoveries of the chemical elements gallium, samarium and dysprosium.-Biography:...
and named after the mineral samarskite
Samarskite
Samarskite is a radioactive rare earth mineral series which includessamarskite- with formula: 22O8and samarskite- with formula 22O8 The formula for smarskite- is also given as: O4...
from which it was isolated. The mineral itself was earlier named after a Russian mine official, Colonel Vasili Samarsky-Bykhovets
Vasili Samarsky-Bykhovets
Vasili Evgrafovich Samarsky–Bykhovets was a Russian mining engineer and the chief of Russian Mining Engineering Corps between 1845 and 1861. The mineral samarskite and chemical element samarium are named after him...
, who thereby became the first person to have a chemical element named after him, albeit indirectly. Although classified as a rare earth element
Rare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
, samarium is the 40th most abundant element in the Earth's crust and is more common than such metals as tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
. Samarium occurs with concentration up to 2.8% in several minerals including cerite
Cerite
Cerite is a complex silicate mineral group containing cerium, formula 963. The cerium and lanthanum content varies with the Ce rich species and the La rich species...
, gadolinite
Gadolinite
Gadolinite, sometimes also known as Ytterbite, is a silicate mineral which consists principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula 2FeBe2Si2O10...
, samarskite
Samarskite
Samarskite is a radioactive rare earth mineral series which includessamarskite- with formula: 22O8and samarskite- with formula 22O8 The formula for smarskite- is also given as: O4...
, monazite
Monazite
Monazite is a reddish-brown phosphate mineral containing rare earth metals. It occurs usually in small isolated crystals. There are actually at least four different kinds of monazite, depending on relative elemental composition of the mineral:...
and bastnäsite
Bastnasite
The mineral bastnäsite is one of a family of three carbonate-fluoride minerals, which includes bastnäsite- with a formula of CO3F, bastnäsite- with a formula of CO3F, and bastnäsite- with a formula of CO3F. Most bastnäsite is bastnäsite-, and cerium is by far the most common of the rare earths in...
, the last two being the most common commercial sources of the element. These minerals are mostly found in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, the USA, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
; China is by far the world leader in samarium mining and production.
The major commercial application of samarium is in samarium-cobalt magnet
Samarium-cobalt magnet
A samarium–cobalt magnet, a type of rare earth magnet, is a strong permanent magnet made of an alloy of samarium and cobalt. They were developed in the early 1970s. They are generally the second-strongest type of magnet made, less strong than neodymium magnets, but have higher temperature ratings...
s which have permanent magnetization
Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.A permanent magnet is an object...
second only to neodymium magnet
Neodymium magnet
A neodymium magnet , the most widely-used type of rare-earth magnet, is a permanent magnet made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. Developed in 1982 by General Motors and Sumitomo Special Metals, neodymium magnets are the strongest...
s; however, samarium compounds can withstand significantly higher temperatures, above 700 °C, without losing their magnetic properties. Radioactive isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
samarium-153
Samarium-153
Samarium-153 is an isotope of samarium.It emits beta particles and gamma rays. It is used in Samarium lexidronam....
is the major component of the drug samarium (153Sm) lexidronam (Quadramet) which kills cancer cells in the treatment of lung cancer
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
, prostate cancer
Prostate cancer
Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...
, breast cancer
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
and osteosarcoma
Osteosarcoma
Osteosarcoma is an aggressive cancerous neoplasm arising from primitive transformed cells of mesenchymal origin that exhibit osteoblastic differentiation and produce malignant osteoid...
. Another isotope, samarium-149, is a strong neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
absorber and is therefore added to the control rod
Control rod
A control rod is a rod made of chemical elements capable of absorbing many neutrons without fissioning themselves. They are used in nuclear reactors to control the rate of fission of uranium and plutonium...
s of nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s. It is also formed as a decay product during the reactor operation and is one of the important factors considered in the reactor design and operation. Other applications of samarium include catalysis
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
of chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
s, radioactive dating
Samarium-neodymium dating
Samarium-neodymium dating is useful for determining the age relationships of rocks and meteorites, based on decay of a long-lived samarium isotope to a radiogenic neodymium isotope. Nd isotope ratios are used to provide information on the source of igneous melts as well as to provide age data...
and an X-ray laser
X-ray laser
An X-ray laser is a device that uses stimulated emission to generate or amplify electromagnetic radiation in the near X-ray or extreme ultraviolet region of the spectrum, that is, usually on the order of several of tens of nanometers wavelength.Because of high gain in the lasing medium, short...
.
Physical properties
Samarium is a rare earth metalRare earth element
As defined by IUPAC, rare earth elements or rare earth metals are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium...
having the hardness and density similar to those of zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
. With the boiling point of 1794 °C, samarium is the third most volatile lanthanide after ytterbium
Ytterbium
Ytterbium is a chemical element with the symbol Yb and atomic number 70. A soft silvery metallic element, ytterbium is a rare earth element of the lanthanide series and is found in the minerals gadolinite, monazite, and xenotime. The element is sometimes associated with yttrium or other related...
and europium
Europium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
; this property facilitates separation of samarium from the mineral ore. At ambient conditions, samarium normally assumes a trigonal structure (α form). Upon heating to 731 °C, its crystal symmetry changes into hexagonal close-packed
Hexagonal crystal system
In crystallography, the hexagonal crystal system is one of the 7 crystal systems, the hexagonal lattice system is one of the 7 lattice systems, and the hexagonal crystal family is one of the 6 crystal families...
(hcp), however the transition temperature depends on the metal purity. Further heating to 922 °C transforms the metal into a body-centered cubic
Cubic crystal system
In crystallography, the cubic crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals....
(bcc) phase. Heating to 300 °C combined with compression to 40 kbar
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...
results in a double-hexagonal close-packed structure (dhcp). Applying higher pressure of the order of hundreds or thousands of kilobars induces a series of phase transformations, in particular with a tetragonal
Tetragonal crystal system
In crystallography, the tetragonal crystal system is one of the 7 lattice point groups. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the cube becomes a rectangular prism with a square base and height .There are two tetragonal Bravais...
phase appearing at about 900 kbar. In one study, the dhcp phase could be produced without compression, using a nonequilibrium annealing regime with a rapid temperature change between about 400 and 700 °C, confirming the transient character of this samarium phase. Also, thin films of samarium obtained by vapor deposition may contain the hcp or dhcp phases at ambient conditions.
Samarium (and its sesquioxide
Sesquioxide
A sesquioxide is an oxide containing three atoms of oxygen with two atoms of another element. For example, aluminium oxide is a sesquioxide.Many sesquioxides contain the metal in the +3 oxidation state and the oxide ion, e.g., Al2O3, La2O3...
) are paramagnetic
Paramagnetism
Paramagnetism is a form of magnetism whereby the paramagnetic material is only attracted when in the presence of an externally applied magnetic field. In contrast with this, diamagnetic materials are repulsive when placed in a magnetic field...
at room temperature. Their corresponding effective magnetic moments, below 2µB, are the 3rd lowest among the lanthanides (and their oxides) after lanthanum and lutetium. The metal transforms to an antiferromagnetic
Antiferromagnetism
In materials that exhibit antiferromagnetism, the magnetic moments of atoms or molecules, usuallyrelated to the spins of electrons, align in a regular pattern with neighboring spins pointing in opposite directions. This is, like ferromagnetism and ferrimagnetism, a manifestation of ordered magnetism...
state upon cooling to 14.8 K. Individual samarium atoms can be isolated by encapsulating them into fullerene
Fullerene
A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are also called buckyballs, and they resemble the balls used in association football. Cylindrical ones are called carbon nanotubes or buckytubes...
molecules. They can also be doped between the C60 molecules in the fullerene
Fullerene
A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are also called buckyballs, and they resemble the balls used in association football. Cylindrical ones are called carbon nanotubes or buckytubes...
solid, rendering it superconductive
Superconductivity
Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...
at temperatures below 8 K. Samarium doping of iron-based superconductor
Iron-based superconductor
Iron-based superconductors are chemical compounds with superconducting properties. In 2008, led by recently discovered iron pnictide compounds , they were in the first stages of experimentation and implementation...
s – the most recent class of high-temperature superconductors – allows to enhance their transition temperature to 56 K, which is the highest value achieved so far in this series.
Chemical properties
Freshly prepared samarium has a silvery luster. In air, it slowly oxidizes at room temperature and spontaneously ignites at 150 °CCelsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
. Even when stored under mineral oil
Mineral oil
A mineral oil is any of various colorless, odorless, light mixtures of alkanes in the C15 to C40 range from a non-vegetable source, particularly a distillate of petroleum....
, samarium gradually oxidizes and develops a grayish-yellow powder of the oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
-hydroxide
Hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
mixture at the surface. The metallic appearance of a sample can be preserved by sealing it under an inert gas such as argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
.
Samarium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form samarium hydroxide:
- 2 Sm (s) + 6 H2O (l) → 2 Sm(OH)3 (aq) + 3 H2 (g)
Samarium dissolves readily in dilute sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
to form solutions containing the yellow to pale green Sm(III) ions, which exist as [Sm(OH2)9]3+ complexes:
- 2 Sm (s) + 3 H2SO4 (aq) → 2 Sm3+ (aq) + 3 SO (aq) + 3 H2 (g)
Samarium is one of the few lanthanides that exhibit the oxidation state +2. The Sm2+ ions are blood-red in solutions.
Compounds
| Formula | color | symmetry | space group Space group In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct... |
No | Pearson symbol Pearson symbol The Pearson symbol, or Pearson notation, is used in crystallography as a means of describing a crystal structure, and was originated by W.B. Pearson. The symbol is made up of two letters followed by a number. For example:* Diamond structure, cF8... |
a (pm) | b (pm) | c (pm) | Z | density, g/cm3 |
|---|---|---|---|---|---|---|---|---|---|---|
| Sm | silvery | trigonal | Rm | 166 | hR9 | 362.9 | 362.9 | 2621.3 | 9 | 7.52 |
| Sm | silvery | hexagonal | P63/mmc | 194 | hP4 | 362 | 362 | 1168 | 4 | 7.54 |
| Sm | silvery | tetragonal | I4/mmm | 139 | tI2 | 240.2 | 240.2 | 423.1 | 2 | 20.46 |
| SmO | golden | cubic | Fmm | 225 | cF8 | 494.3 | 494.3 | 494.3 | 4 | 9.15 |
| Sm2O3 | trigonal | Pm1 | 164 | hP5 | 377.8 | 377.8 | 594 | 1 | 7.89 | |
| Sm2O3 | monoclinic | C2/m | 12 | mS30 | 1418 | 362.4 | 885.5 | 6 | 7.76 | |
| Sm2O3 | cubic | Ia | 206 | cI80 | 1093 | 1093 | 1093 | 16 | 7.1 | |
| SmH2 | cubic | Fmm | 225 | cF12 | 537.73 | 537.73 | 537.73 | 4 | 6.51 | |
| SmH3 | hexagonal | Pc1 | 165 | hP24 | 377.1 | 377.1 | 667.2 | 6 | ||
| Sm2B5 | gray | monoclinic | P21/c | 14 | mP28 | 717.9 | 718 | 720.5 | 4 | 6.49 |
| SmB2 | hexagonal | P6/mmm | 191 | hP3 | 331 | 331 | 401.9 | 1 | 7.49 | |
| SmB4 | tetragonal | P4/mbm | 127 | tP20 | 717.9 | 717.9 | 406.7 | 4 | 6.14 | |
| SmB6 | cubic | Pmm | 221 | cP7 | 413.4 | 413.4 | 413.4 | 1 | 5.06 | |
| SmB66 | cubic | Fmc | 226 | cF1936 | 2348.7 | 2348.7 | 2348.7 | 24 | 2.66 | |
| Sm2C3 | cubic | I3d | 220 | cI40 | 839.89 | 839.89 | 839.89 | 8 | 7.55 | |
| SmC2 | tetragonal | I4/mmm | 139 | tI6 | 377 | 377 | 633.1 | 2 | 6.44 | |
| SmF2 | purple | cubic | Fmm | 225 | cF12 | 587.1 | 587.1 | 587.1 | 4 | 6.18 |
| SmF3 | white | orthorhombic | Pnma | 62 | oP16 | 667.22 | 705.85 | 440.43 | 4 | 6.64 |
| SmCl2 | brown | orthorhombic | Pnma | 62 | oP12 | 756.28 | 450.77 | 901.09 | 4 | 4.79 |
| SmCl3 | yellow | hexagonal | P63/m | 176 | hP8 | 737.33 | 737.33 | 416.84 | 2 | 4.35 |
| SmBr2 | brown | orthorhombic | Pnma | 62 | oP12 | 797.7 | 475.4 | 950.6 | 4 | 5.72 |
| SmBr3 | yellow | orthorhombic | Cmcm | 63 | oS16 | 404 | 1265 | 908 | 2 | 5.58 |
| SmI2 | green | monoclinic | P21/c | 14 | mP12 | |||||
| SmI3 | orange | trigonal | R | 63 | hR24 | 749 | 749 | 2080 | 6 | 5.24 |
| SmN | cubic | Fmm | 225 | cF8 | 357 | 357 | 357 | 4 | 8.48 | |
| SmP | cubic | Fmm | 225 | cF8 | 576 | 576 | 576 | 4 | 6.3 | |
| SmAs | cubic | Fmm | 225 | cF8 | 591.5 | 591.5 | 591.5 | 4 | 7.23 |
Oxides
The most stable oxide of samarium is the sesquioxideSesquioxide
A sesquioxide is an oxide containing three atoms of oxygen with two atoms of another element. For example, aluminium oxide is a sesquioxide.Many sesquioxides contain the metal in the +3 oxidation state and the oxide ion, e.g., Al2O3, La2O3...
Sm2O3. As many other samarium compounds, it exists in several crystalline phases. The trigonal form is obtained by slow cooling from the melt. The melting point of Sm2O3 is rather high (2345 °C) and therefore melting is usually achieved not by direct heating, but with induction heating
Induction heating
Induction heating is the process of heating an electrically conducting object by electromagnetic induction, where eddy currents are generated within the metal and resistance leads to Joule heating of the metal...
, through a radio-frequency coil. The Sm2O3 crystals of monoclinic symmetry can be grown by the flame fusion method (Verneuil process
Verneuil process
The Verneuil process, also called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in 1902 by the French chemist Auguste Verneuil. It is primarily used to produce the ruby and sapphire varieties of corundum, as well as the diamond simulants...
) from the Sm2O3 powder, that yields cylindrical boules up to several centimeters long and about one centimeter in diameter. The boules are transparent when pure and defect-free and are orange otherwise. Heating the metastable trigonal Sm2O3 to 1900 °C converts it to the more stable monoclinic phase. Cubic Sm2O3 has also been described.
Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm2O3 with samarium metal at elevated temperature (1000 °C) and pressure above 50 kbar; lowering the pressure resulted in an incomplete reaction. SmO has the cubic rock-salt lattice structure.
Chalcogenides
Samarium forms trivalent sulfideSamarium(III) sulfide
Samarium sulfide is a chemical compound....
, selenide
Selenide
A selenide is a chemical compound in which selenium serves as an anion with oxidation number of −2 , much as sulfur does in a sulfide. The chemistry of the selenides and sulfides are similar....
and telluride
Telluride (chemistry)
The telluride ion is Te2−. It is the final stable member of the series of dianions O2−, S2−, and Se2− ....
. Divalent chalcogenides SmS, SmSe and SmTe with cubic rock-salt crystal structure are also known. They are remarkable by converting from semiconducting to metallic state at room temperature upon application of pressure. Whereas the transition is continuous and occurs at about 20–30 kbar in SmSe and SmTe, it is abrupt in SmS and requires only 6.5 kbar. This effect results in spectacular color change in SmS from black to golden yellow when its crystals of films are scratched or polished. The transition does not change lattice symmetry, but there is a sharp decrease (~15%) in the crystal volume. It shows hysteresis, that is when the pressure is released, SmS returns to the semiconducting state at much lower pressure of about 0.4 kbar.
Halides
Samarium metal reacts with all the halogens X = F, Cl, Br or I, forming trihalides:- 2 Sm (s) + 3 X2 (g) → 2 SmX3 (s)
Their further reduction with samarium, lithium or sodium metals at elevated temperatures (about 700–900 °C) yields dihalides. The diiodide can also be prepared by heating SmI3, or by reacting the metal with 1,2-diiodoethane in anhydrous tetrahydrofuran
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
at room temperature:
- Sm (s) + ICH2-CH2I → SmI2 + CH2=CH2
In addition to dihalides, the reduction also produces numerous non-stoichiometric
Non-stoichiometric compound
Non-stoichiometric compounds are chemical compounds with an elemental composition that cannot be represented by a ratio of well-defined natural numbers, and therefore violate the law of definite proportions. Often, they are solids that contain crystallographic point defects, such as interstitial...
samarium halides with a well-defined crystal structure, such as Sm3F7, Sm14F33, Sm27F64, Sm11Br24, Sm5Br11 and Sm6Br13
As reflected in the table above, samarium halides change their crystal structures when one type of halide atoms is substituted for another, which is an uncommon behavior for most elements (e. g. actinides). Many halides have two major crystal phases for one composition, one being significantly more stable and another being metastable. The latter is formed upon compression or heating, followed by quenching to ambient conditions. For example, compressing the usual monoclinic samarium diiodide and releasing the pressure results in a PbCl2-type orthorhombic structure (density 5.90 g/cm3), and similar treatment results in a new phase of samarium triiodide (density 5.97 g/cm3).
Borides
SinteringSintering
Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature...
powders of samarium oxide and boron, in vacuum, yields a powder containing several samarium boride phases, and their volume ratio can be controlled through the mixing proportion. The powder can be converted into larger crystals of a certain samarium boride using arc melting
Electric arc furnace
An electric arc furnace is a furnace that heats charged material by means of an electric arc.Arc furnaces range in size from small units of approximately one ton capacity up to about 400 ton units used for secondary steelmaking...
or zone melting
Zone melting
Zone melting is a group of similar methods of purifying crystals, in which a narrow region of a crystal is molten, and this molten zone is moved along the crystal...
techniques, relying on the different melting/crystallization temperature of SmB6 (2580 °C), SmB4 (about 2300 °C) and SmB66 (2150 °C). All these materials are hard, brittle, dark-gray solids with the hardness increasing with the boron content. Samarium diboride is too volatile to be produced with these methods and requires high pressure (about 65 kbar) and low temperatures between 1140 and 1240 °C to stabilize its growth. Increasing the temperature results in the preferential formations of SmB6.
Samarium hexaboride is a typical intermediate-valence compound where samarium is present both as Sm2+ and Sm3+ ions at the ratio 3:7. It belongs to a class of Kondo insulator
Kondo insulator
In solid-state physics, Kondo insulators are understood as materials with strongly correlated electrons, that open up a narrow band gap at low temperatures with the chemical potential lying in the gap, whereas in heavy fermions the chemical potential is located in the...
s, that is at high temperatures (above 50 K), its properties are typical of a Kondo metal, with metallic electrical conductivity characterized by strong electron scattering, whereas at low temperatures, it behaves as a non-magnetic insulator with a narrow band gap
Band gap
In solid state physics, a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference between the top of the valence band and the...
of about 4–14 meV. The cooling-induced metal-insulator transition in SmB6 is accompanied by a sharp increase in the thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
, peaking at about 15 K. The reason for this increase is that electrons themselves do not contribute to the thermal conductivity at low temperatures, which is dominated by phonon
Phonon
In physics, a phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, such as solids and some liquids...
s, but the decrease in electron concentration reduced the rate of electron-phonon scattering.
Other inorganic compounds
Samarium carbideCarbide
In chemistry, a carbide is a compound composed of carbon and a less electronegative element. Carbides can be generally classified by chemical bonding type as follows: salt-like, covalent compounds, interstitial compounds, and "intermediate" transition metal carbides...
s are prepared by melting a graphite-metal mixture in an inert atmosphere. After the synthesis, they are unstable in air and are studied also under inert atmosphere. Samarium monophosphide SmP is a semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
with the bandgap of 1.10 eV, the same as in silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, and high electrical conductivity of n-type
N-type semiconductor
N-type semiconductors are a type of extrinsic semiconductor where the dopant atoms are capable of providing extra conduction electrons to the host material . This creates an excess of negative electron charge carriers....
. It can be prepared by annealing at 1100 °C an evacuated quartz ampoule containing mixed powders of phosphorus and samarium. Phosphorus is highly volatile at high temperatures and may explode, thus the heating rate has to be kept well below 1 °C/min. Similar procedure is adopted for the monarsenide SmAs, but the synthesis temperature is higher at 1800 °C.
A large number of crystalline binary compounds are known for samarium and one of the group-4, 5 or 6 element X, where X is Si, Ge, Sn, Pb, Sb or Te, and metallic alloys of samarium form another large group. They are all prepared by annealing mixed powders of the corresponding elements. Many of the resulting compounds are non-stoichiometric and have nominal compositions SmaXb, where the b/a ratio varies between 0.5 and 3.
Organometallic compounds
Samarium forms a cyclopentadienideCyclopentadiene
Cyclopentadiene is an organic compound with the formula C5H6. This colorless liquid has a strong and unpleasant odor. At room temperature, this cyclic diene dimerizes over the course of hours to give dicyclopentadiene via a Diels–Alder reaction...
Sm(C5H5)3 and its chloroderivatives Sm(C5H5)2Cl and Sm(C5H5)Cl2. They are prepared by reacting samarium trichloride with NaC5H5 in tetrahydrofuran
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
. Contrary to cyclopentadienides of most other lanthanides, in Sm(C5H5)3 some C5H5 rings bridge each other by forming ring vertexes η1 or edges η2 toward another neighboring samarium atom, thereby creating polymeric chains. The chloroderivative Sm(C5H5)2Cl has a dimer structure which is more accurately expressed as (η5-C5H5)2Sm(µ-Cl)2(η5-C5H5)2. There, the chlorine bridges can be replaced, for instance, by iodine, hydrogen or nitrogen atoms or by CN groups.
The (C5H5)– ion in samarium cyclopentadienides can be replaced by the indenide (C9H7)– or cyclooctatetraenide
Cyclooctatetraene
1,3,5,7-Cyclooctatetraene is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as [8]annulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature...
(C8H8)2– ring, resulting in Sm(C9H7)3 or KSm(η8-C8H8)2. The latter compound has a similar structure to that of uranocene
Uranocene
Uranocene U2 is the most notable cyclooctatetraenide of the f elements and one of the first organouranium compounds to be synthesized. Uranocene is a member of the actinocenes, a group of metallocenes incorporating elements from the actinide series...
. There is also a cyclopentadienide of divalent samarium, Sm(C5H5)2 – a solid which sublimates at about 85 °C. Contrary to ferrocene
Ferrocene
Ferrocene is an organometallic compound with the formula Fe2. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are also known as sandwich compounds...
, the C5H5 rings in Sm(C5H5)2 are not parallel but are tilted by 40°.
Alkyls and aryl
Aryl
In the context of organic molecules, aryl refers to any functional group or substituent derived from an aromatic ring, be it phenyl, naphthyl, thienyl, indolyl, etc....
s of samarium are obtained through a metathesis reaction in tetrahydrofuran or ether
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
:
- SmCl3 + 3 LiR → SmR3 + 3 LiCl
- Sm(OR)3 + 3 LiCH(SiMe3)2 → Sm{CH(SiMe3)2}3 + 3 LiOR
Here R is a hydrocarbon group and Me stands for methyl.
Isotopes
Naturally occurring samarium has a radioactivityRadioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
of 128 Bq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
/g. It is composed of four stable isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s: 144Sm, 150Sm, 152Sm and 154Sm, and three extremely long-lived radioisotopes, 147Sm (half-life t½ = 1.06 years), 148Sm (7 years) and 149Sm (>2 years), with 152Sm being the most abundant (natural abundance
Natural abundance
In chemistry, natural abundance refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the atomic weight listed for the element in the periodic table...
26.75%). 149Sm is listed by various sources either as stable or radioactive isotope.
The long-lived isotopes,146Sm, 147Sm, and 148Sm, primarily decay by emission of alpha particles
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...
to isotopes of neodymium
Neodymium
Neodymium is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal that tarnishes in air. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach. It is present in significant quantities in the ore minerals monazite and bastnäsite...
. Lighter unstable isotopes of samarium primarily decay by electron capture
Electron capture
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
to isotopes of promethium
Promethium
Promethium is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only exclusively radioactive element besides technetium that is followed by chemical elements with stable isotopes.- Prediction :...
, while heavier ones convert through beta decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
to isotopes of europium
Europium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
.
The alpha-decay of 147Sm to 143Nd with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 1.06 years serve for samarium-neodymium dating
Samarium-neodymium dating
Samarium-neodymium dating is useful for determining the age relationships of rocks and meteorites, based on decay of a long-lived samarium isotope to a radiogenic neodymium isotope. Nd isotope ratios are used to provide information on the source of igneous melts as well as to provide age data...
The half-lives of 151Sm and 145Sm are 90 years and 340 days, respectively. All of the remaining radioisotopes have half-lives that are less than 2 days, and the majority of these have half-lives that are less than 48 seconds. Samarium also has five nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
s with the most stable being 141mSm (half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
22.6 minutes), 143m1Sm (t½ = 66 seconds) and 139mSm (t½ = 10.7 seconds).
History
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
chemist Paul Émile Lecoq de Boisbaudran
Paul Emile Lecoq de Boisbaudran
Paul Émile Lecoq de Boisbaudran was a French chemist known for his discoveries of the chemical elements gallium, samarium and dysprosium.-Biography:...
. Boisbaudran isolated samarium oxide and/or hydroxide in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
in 1879 from the mineral samarskite
Samarskite
Samarskite is a radioactive rare earth mineral series which includessamarskite- with formula: 22O8and samarskite- with formula 22O8 The formula for smarskite- is also given as: O4...
((Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16) and identified a new element in it via sharp optical absorption lines. The Swiss chemist Marc Delafontaine
Marc Delafontaine
Marc Delafontaine was a Swiss chemist who in 1878, along with Jacques-Louis Soret, first observed holmium spectroscopically. In 1879, Per Teodor Cleve chemically separated it from thulium and erbium. The three are given credit for the element's discovery....
announced a new element decipium
Decipium
Decipium was the proposed name for a new chemical element isolated by Marc Delafontaine from the mineral samarskite. He published his discovery in 1878 and a followup paper in 1881. Later it was shown that decipium was a mixture of samarium and other rare earth elements....
(from meaning "deceptive, misleading") in 1878, but later in 1880–1881 demonstrated that it was a mixture of several elements, one being identical to the Boisbaudran's samarium. Although samarskite was first found in the remote Russian region of Urals, by the late 1870s its deposits had been located in other places making the mineral available to many researchers. In particular, it was found that the samarium isolated by Boisbaudran was also impure and contained comparable amount of europium
Europium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
. The pure element was produced only in 1901 by Eugène-Anatole Demarçay.
Boisbaudran named his element samaria after the mineral samarskite, which in turn honored Vasili Samarsky-Bykhovets
Vasili Samarsky-Bykhovets
Vasili Evgrafovich Samarsky–Bykhovets was a Russian mining engineer and the chief of Russian Mining Engineering Corps between 1845 and 1861. The mineral samarskite and chemical element samarium are named after him...
(1803–1870). Samarsky-Bykhovets was the Chief of Staff of the Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n Corps of Mining Engineers who granted access for the German mineralogists, brothers Gustav Rose
Gustav Rose
Gustav Rose was a German mineralogist who was a native of Berlin. He was a brother of mineralogist Heinrich Rose , the son of pharmacologist Valentin Rose , and the father of noted surgeon Edmund Rose and the classicist Valentin Rose.He was a graduate of the University of Berlin, where he was a...
and Heinrich Rose
Heinrich Rose
Heinrich Rose was a German mineralogist and analytical chemist. He was the brother of the mineralogist Gustav Rose and a son of Valentin Rose....
, to study the mineral samples from the Urals. In this sense samarium was the first chemical element to be named after a person. Later the name samaria used by Boisbaudran was transformed into samarium, to conform with other element names, and samaria nowadays is sometimes used to refer to samarium oxide, by analogy with yttria, zirconia, alumina, ceria, holmia, etc. The symbol Sm was suggested for samarium; however an alternative Sa was frequently used instead until the 1920s.
Prior to the advent of ion-exchange separation technology in the 1950s, samarium had no commercial uses in pure form. However, a by-product of the fractional crystallization purification of neodymium was a mixture of samarium and gadolinium that acquired the name of "Lindsay Mix" after the company that made it. This material is thought to have been used for nuclear control rod
Control rod
A control rod is a rod made of chemical elements capable of absorbing many neutrons without fissioning themselves. They are used in nuclear reactors to control the rate of fission of uranium and plutonium...
s in some of the early nuclear reactors. Nowadays, a similar commodity product has the name "samarium-europium-gadolinium
Gadolinium
Gadolinium is a chemical element with the symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare-earth metal. It is found in nature only in combined form. Gadolinium was first detected spectroscopically in 1880 by de Marignac who separated its oxide and is credited with...
" (SEG) concentrate. It is prepared by solvent extraction from the mixed lanthanide
Lanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
s isolated from bastnäsite (or monazite). Since the heavier lanthanides have the greater affinity for the solvent used, they are easily extracted from the bulk using relatively small proportions of solvent. Not all rare earth producers who process bastnäsite do so on large enough scale to continue onward with the separation of the components of SEG, which typically makes up only one or two percent of the original ore. Such producers will therefore be making SEG with a view to marketing it to the specialized processors. In this manner, the valuable europium content of the ore is rescued for use in phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
manufacture. Samarium purification follows the removal of the europium. Currently, being in oversupply, samarium oxide is less expensive on a commercial scale than its relative abundance in the ore might suggest.
Occurrence and production
Samarium is not found free in nature, but, like other rare earth elements, is contained in many minerals, including monazite
Monazite
Monazite is a reddish-brown phosphate mineral containing rare earth metals. It occurs usually in small isolated crystals. There are actually at least four different kinds of monazite, depending on relative elemental composition of the mineral:...
, bastnäsite
Bastnasite
The mineral bastnäsite is one of a family of three carbonate-fluoride minerals, which includes bastnäsite- with a formula of CO3F, bastnäsite- with a formula of CO3F, and bastnäsite- with a formula of CO3F. Most bastnäsite is bastnäsite-, and cerium is by far the most common of the rare earths in...
, cerite
Cerite
Cerite is a complex silicate mineral group containing cerium, formula 963. The cerium and lanthanum content varies with the Ce rich species and the La rich species...
, gadolinite
Gadolinite
Gadolinite, sometimes also known as Ytterbite, is a silicate mineral which consists principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula 2FeBe2Si2O10...
and samarskite
Samarskite
Samarskite is a radioactive rare earth mineral series which includessamarskite- with formula: 22O8and samarskite- with formula 22O8 The formula for smarskite- is also given as: O4...
; monazite (in which samarium occurs at concentrations of up to 2.8%) and bastnäsite are mostly used as commercial sources. World resources of samarium are estimated at two million tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s; they are mostly located in China, US, Brazil, India, Sri Lanka and Australia, and the annual production is about 700 tonnes. Country production reports are usually given for all rare-earth metals combined. By far, China has the largest production with 120,000 tonnes mined per year; it is followed by the US (about 5,000 tonnes) and India (2,700 tonnes). Samarium is usually sold as oxide, which at the price of about 30 USD/kg is one of the cheapest lanthanide oxides. Whereas mischmetal
Mischmetal
Mischmetal is an alloy of rare earth elements in various naturally occurring proportions. It is also called cerium mischmetal, rare earth mischmetal or misch metal. A typical composition includes approximately 50% cerium and 25% lanthanum, with small amounts of neodymium and praseodymium...
– a mixture of rare earth metals containing about 1% of samarium – has long been used, relatively pure samarium has been isolated only recently, through ion exchange
Ion exchange
Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion...
processes, solvent extraction techniques, and electrochemical deposition. The metal is often prepared by electrolysis of a molten mixture of samarium(III) chloride
Samarium(III) chloride
Samarium chloride , also known as samarium trichloride, is a compound of samarium and chlorine. It is a pale yellow solid which rapidly absorbs water on exposure to moist air to form a hexahydrate, SmCl3.6H2O. Simple rapid heating of the hydrate alone may cause small amounts of hydrolysis...
with sodium chloride
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
or calcium chloride
Calcium chloride
Calcium chloride, CaCl2, is a salt of calcium and chlorine. It behaves as a typical ionic halide, and is solid at room temperature. Common applications include brine for refrigeration plants, ice and dust control on roads, and desiccation...
. Samarium can also be obtained by reducing its oxide with lanthanum
Lanthanum
Lanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and...
. The product is then distilled to separate samarium (boiling point 1794 °C) and lanthanum (b. p. 3464 °C).
Samarium-151 is produced in nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
with the yield of about
0.4% of the total number of fission events. It is also synthesized upon neutron capture
Neutron capture
Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge they can enter a nucleus more easily than positively charged protons, which are repelled...
by samarium-149, which is added to the control rod
Control rod
A control rod is a rod made of chemical elements capable of absorbing many neutrons without fissioning themselves. They are used in nuclear reactors to control the rate of fission of uranium and plutonium...
s of nuclear reactors. Consequently, samarium-151 is present in spent nuclear fuel
Nuclear fuel
Nuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
and radioactive waste.
Applications
Samarium-cobalt magnet
A samarium–cobalt magnet, a type of rare earth magnet, is a strong permanent magnet made of an alloy of samarium and cobalt. They were developed in the early 1970s. They are generally the second-strongest type of magnet made, less strong than neodymium magnets, but have higher temperature ratings...
s, which have a nominal composition of SmCo5 or Sm2Co17. They have high permanent magnetization, which is about 10,000 times that of iron and is second only to that of neodymium magnet
Neodymium magnet
A neodymium magnet , the most widely-used type of rare-earth magnet, is a permanent magnet made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. Developed in 1982 by General Motors and Sumitomo Special Metals, neodymium magnets are the strongest...
s. However, samarium-based magnets have higher resistance to demagnetization, as they are stable to temperatures above 700 °C (cf. 300–400 °C for neodymium magnets). These magnets are found in small motors, headphones, high-end magnetic pickups for guitars and related musical instruments. For example, they are used in the motors of a solar-powered
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...
electric aircraft Solar Challenger
Solar Challenger
|-See also:-External links:*...
and in the Samarium Cobalt Noiseless
Vintage Noiseless
The Vintage Noiseless series is a line of electric guitar pickups made by Fender. Introduced in 1998, they feature a stacked-coil design. The range includes models for electric guitars and basses. The Vintage Noiseless pickups were an original equipment material on the American Deluxe series...
electric guitar and bass pickups.
Another important application of samarium and its compounds is as catalyst and chemical reagent. Samarium catalysts assist decomposition of plastics, dechlorination of pollutants such as polychlorinated biphenyl
Polychlorinated biphenyl
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...
s (PCBs), as well as the dehydration and dehydrogenation
Dehydrogenation
Dehydrogenation is a chemical reaction that involves the elimination of hydrogen . It is the reverse process of hydrogenation. Dehydrogenation reactions may be either large scale industrial processes or smaller scale laboratory procedures....
of ethanol. Samarium(III) triflate (Sm(OTf)3, that is Sm(CF3SO3)3) is one of the most efficient Lewis acid
Lewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
catalysts for a halogen-promoted Friedel–Crafts reaction with alkenes. Samarium(II) iodide
Samarium(II) iodide
Samarium iodide is a green solid composed of samarium and iodine, with a melting point of 520 °C where the samarium atom has a coordination number of seven in a capped octahedral configuration...
is a very common reducing and coupling agent in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
, for example in the desulfonylation reactions
Desulfonylation reactions
Desulfonylation reactions are chemical reactions leading to the removal of a sulfonyl group from organic compounds. As the sulfonyl functional group is electron-withdrawing, methods for cleaving the sulfur-carbon bonds of sulfones are typically reductive in nature...
; annulation
Annulation
Annulation in organic chemistry is a chemical reaction in which a new ring is constructed on another molecule ....
; Danishefsky
Danishefsky Taxol total synthesis
The Danishefsky Taxol total synthesis in organic chemistry is an important third Taxol synthesis published by the group of Samuel Danishefsky in 1996...
, Kuwajima
Kuwajima Taxol total synthesis
The Kuwajima Taxol total synthesis by the group of Isao Kuwajima of the Tokyo Institute of Technology is one of several efforts in taxol total synthesis published in the 1990s...
, Mukaiyama
Mukaiyama Taxol total synthesis
The Mukaiyama taxol total synthesis published by the group of Teruaki Mukaiyama of the Tokyo University of Science between 1997 and 1999 was the 6th successful taxol total synthesis. The total synthesis of Taxol is considered a hallmark in organic synthesis....
and Holton Taxol total syntheses
Holton Taxol total synthesis
The Holton Taxol total synthesis, published by Robert A. Holton and his group at Florida State University in 1994 was the first total synthesis of Taxol ....
; strychnine total synthesis
Strychnine total synthesis
Strychnine total synthesis in chemistry describes the total synthesis of the complex biomolecule strychnine. The first reported method by the group of Robert Burns Woodward in 1954 is considered a classic in this research field....
; Barbier reaction
Barbier reaction
The Barbier reaction is an organic reaction between an alkyl halide and a carbonyl group as an electrophilic substrate in the presence of magnesium, aluminium, zinc, indium, tin or its salts. The reaction product is a primary, secondary or tertiary alcohol...
and other reductions with samarium(II) iodide
Reductions with samarium(II) iodide
Reductions with samarium iodide involve the conversion of various classes of organic compounds into reduced products through the action of samarium iodide, a mild one-electron reducing agent.-Introduction:...
.
In its usual oxidized form, samarium is added to ceramics and glasses where it increases absorption of infrared light. As a (minor) part of mischmetal
Mischmetal
Mischmetal is an alloy of rare earth elements in various naturally occurring proportions. It is also called cerium mischmetal, rare earth mischmetal or misch metal. A typical composition includes approximately 50% cerium and 25% lanthanum, with small amounts of neodymium and praseodymium...
, samarium is found in "flint
Flint
Flint is a hard, sedimentary cryptocrystalline form of the mineral quartz, categorized as a variety of chert. It occurs chiefly as nodules and masses in sedimentary rocks, such as chalks and limestones. Inside the nodule, flint is usually dark grey, black, green, white, or brown in colour, and...
" ignition device of many lighter
Lighter
A lighter is a portable device used to generate a flame. It consists of a metal or plastic container filled with a flammable fluid or pressurized liquid gas, a means of ignition, and some provision for extinguishing the flame.- History :...
s and torches.
Radioactive samarium-153 is a beta emitter with a half-life of 46.3 hours. It is used to kill cancer cells in the treatment of lung cancer
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
, prostate cancer
Prostate cancer
Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...
, breast cancer
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
and osteosarcoma
Osteosarcoma
Osteosarcoma is an aggressive cancerous neoplasm arising from primitive transformed cells of mesenchymal origin that exhibit osteoblastic differentiation and produce malignant osteoid...
. For this purpose, samarium-153 is chelated
Chelation
Chelation is the formation or presence of two or more separate coordinate bonds between apolydentate ligand and a single central atom....
with ethylene diamine tetramethylene phosphonate (EDTMP
EDTMP
EDTMP or ethylenediamine tetra is a phosphonic acid. It has chelating and anti corrosion properties. EDTMP is the phosphonate analog of EDTA.-Properties:...
) and injected intravenously. The chelation prevents accumulation of radioactive samarium in the body that would result in excessive irradiation and generation of new cancer cells. The corresponding drug has several names including samarium (153Sm) lexidronam and its trade name is Quadramet.
Samarium-149 has high cross-section for neutron capture
Neutron capture
Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge they can enter a nucleus more easily than positively charged protons, which are repelled...
(41,000 barns
Barn (unit)
A barn is a unit of area. Originally used in nuclear physics for expressing the cross sectional area of nuclei and nuclear reactions, today it is used in all fields of high energy physics to express the cross sections of any scattering process, and is best understood as a measure of the...
) and is therefore used in the control rods of nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s. Its advantage compared to competing materials, such as boron and cadmium, is stability of absorption – most of the fusion and decay products of samarium-149 are other isotopes of samarium which are also good neutron absorbers. For example, the cross sections of samarium-151 is 15,000 barns, it is on the order of hundred barns for samarium-150, 152, 153, and is 6,800 barns for natural (mixed-isotope) samarium. Among the decay products in a nuclear reactor, samarium-149 is regarded as the second most important for the reactor design and operation after xenon-135
Xenon-135
Xenon-135 is an unstable isotope of xenon with a half-life of about 9.2 hours. 135Xe is a fission product of uranium and Xe-135 is the most powerful known neutron-absorbing nuclear poison , with a significant effect on nuclear reactor operation...
.
Non-commercial and potential applications
Samarium-doped calcium fluorideCalcium fluoride
Calcium fluoride is the inorganic compound with the formula CaF2. This ionic compound of calcium and fluorine occurs naturally as the mineral fluorite . It is the source of most of the world's fluorine. This insoluble solid adopts a cubic structure wherein calcium is coordinated to eight fluoride...
crystals were used as an active medium in one of the first solid-state laser
Solid-state laser
A solid-state laser is a laser that uses a gain medium that is a solid, rather than a liquid such as in dye lasers or a gas as in gas lasers. Semiconductor-based lasers are also in the solid state, but are generally considered as a separate class from solid-state lasers .-Solid-state...
s designed and constructed by Peter Sorokin
P. P. Sorokin
Peter P. Sorokin is an American physicist and co-inventor of the dye laser. Sorokin and his colleague J. R. Lankard, at IBM Research Laboratories, used a ruby laser to excite a near infrared laser dye. Their report was quickly followed by that of F. P. Schäfer. In 1974 Sorokin received the Albert...
(co-inventor of the dye laser
Dye laser
A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a much wider range of wavelengths. The wide bandwidth makes them particularly suitable for tunable lasers and...
) and Mirek Stevenson at IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
research labs in early 1961. This samarium laser emitted pulses of red light at 708.5 nm. It had to be cooled by liquid helium and thus did not find practical applications.
Another samarium-based laser became the first saturated X-ray laser
X-ray laser
An X-ray laser is a device that uses stimulated emission to generate or amplify electromagnetic radiation in the near X-ray or extreme ultraviolet region of the spectrum, that is, usually on the order of several of tens of nanometers wavelength.Because of high gain in the lasing medium, short...
operating at wavelengths shorter than 10 nanometers. It provided 50-picosecond pulses at 7.3 and 6.8 nm suitable for applications in holography
Holography
Holography is a technique that allows the light scattered from an object to be recorded and later reconstructed so that when an imaging system is placed in the reconstructed beam, an image of the object will be seen even when the object is no longer present...
, high-resolution microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...
of biological specimens, deflectometry, interferometry
Interferometry
Interferometry refers to a family of techniques in which electromagnetic waves are superimposed in order to extract information about the waves. An instrument used to interfere waves is called an interferometer. Interferometry is an important investigative technique in the fields of astronomy,...
and radiography
Radiography
Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
of dense plasmas related to confinement fusion and astrophysics
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
. Saturated operation meant that the maximum possible power was extracted from the lasing medium, resulting in the high peak energy of 0.3 mJ. The active medium was samarium plasma produced by irradiating samarium-coated glass with a pulsed infrared Nd-glass laser
Nd:YAG laser
Nd:YAG is a crystal that is used as a lasing medium for solid-state lasers. The dopant, triply ionized neodymium, typically replaces yttrium in the crystal structure of the yttrium aluminium garnet , since they are of similar size...
(wavelength ~1.05 µm).
The change in electrical resistivity in samarium monochalcogenides
Samarium monochalcogenides
Samarium monochalcogenides are chemical compounds with the composition SmX, where Sm stands for the lanthanide element samarium and X denotes any one of three chalcogen elements, sulfur, selenium or tellurium, resulting in the compounds SmS, SmSe or SmTe...
can be used in a pressure sensor or in a memory device triggered between a low-resistance and high-resistance state by external pressure, and such devices are being developed commercially. Samarium monosulfide also generates electric voltage upon moderate heating to about 150 °C that can be applied in thermoelectric power converters.
The analysis of relative concentrations of samarium and neodymium isotopes 147Sm, 144Nd and 143Nd allows the determination of the age and origin of rocks and meteorites in samarium-neodymium dating
Samarium-neodymium dating
Samarium-neodymium dating is useful for determining the age relationships of rocks and meteorites, based on decay of a long-lived samarium isotope to a radiogenic neodymium isotope. Nd isotope ratios are used to provide information on the source of igneous melts as well as to provide age data...
. Both elements are lanthanides and have very similar physical and chemical properties. Therefore, Sm-Nd dating is either insensitive to partitioning of the marker elements during various geological processes, or such partitioning can well be understood and modeled from the ionic radii
Ionic radius
Ionic radius, rion, is the radius of an atom's ion. Although neither atoms nor ions have sharp boundaries, it is important to treat them as if they are hard spheres with radii such that the sum of ionic radii of the cation and anion gives the distance between the ions in a crystal lattice...
of the involved elements.
Health issues
Samarium metal has no biological role in human body. Its salts stimulate metabolism, but it is unclear whether this is the effect of samarium or other lanthanides present with it. The total amount of samarium in adults is about 50 micrograms, mostly in liver and kidneys and with about 8 micrograms per liter being dissolved in the blood. Samarium is not absorbed by plants to a measurable concentration and therefore is normally not a part of human diet. However, a few plants and vegetables may contain up to 1 part per million of samarium. Insoluble salts of samarium are non-toxic and the soluble ones are only slightly toxic.When ingested, only about 0.05% of samarium salts is absorbed into the bloodstream and the remainder is excreted. From the blood, about 45% goes to the liver and 45% is deposited on the surface of the bones where it remains for about 10 years; the balance 10% is excreted.