Germanium dioxide
Encyclopedia
Germanium dioxide, also called germanium oxide and germania, is an inorganic compound
, an oxide
of germanium
. Its chemical formula is Ge
O
2. Other names include germanic acid, G-15, and ACC10380. It forms as a passivation layer on pure germanium in contact with atmospheric oxygen.
4);
tetragonal GeO2 (the mineral argutite
) has the rutile
-like structure of stishovite
(germanium having coordination number 6); and amorphous (glassy) GeO2 is similar to fused silica.
Germanium dioxide can be prepared in both crystalline and amorphous forms. At ambient pressure the amorphous structure is formed by a network of GeO4 tetrahedra. At elevated pressure up to approximately 9 GPa the germanium average coordination number
steadily increases from 4 to around 5 with a corresponding increase in the Ge-O bond distance. At higher pressures, up to approximately 15 GPa, the germanium coordination number
increases to 6 and the dense network structure is composed of GeO6 octahedra. When the pressure is subsequently reduced, the structure reverts back to the tetrahedral form. At high pressure, the rutile form converts to an orthorhombic CaCl2 form.
at 1000 °C forms germanium monoxide
(GeO).
The rutile form of germanium dioxide is more soluble than the hexagonal form and dissolves to form germanic acid, H4GeO4 or Ge(OH)4. GeO2 is only slightly soluble in acid but dissolves more readily in alkali to give germanates.
Germanium dioxide is not flammable. In contact with hydrochloric acid
, it releases the volatile and corrosive germanium tetrachloride
.
(1.7) of germanium dioxide and optical dispersion properties makes it useful as an optical material for wide-angle lens
es and in optical microscope
objective
lenses
. It is transparent in infrared
.
A mixture of silicon dioxide and germanium dioxide ("silica-germania") is used as an optical material for optical fiber
s and optical waveguides. Controlling the ratio of the elements allows precise control of refractive index. Silica-germania glasses have lower viscosity and higher refractive index than pure silica. Germania replaced titania
as the silica dopant for silica fiber, eliminating the need for subsequent heat treatment, which made the fibers brittle.
Germanium dioxide is also used as a catalyst in production of polyethylene terephthalate
resin, and for production of other germanium compounds. It is used as a feedstock for production of some phosphor
s and semiconductor materials.
In the manufacture of integrated circuits and transistors, germanium dioxide is a rather poor dielectric and is chemically unstable, which is one of the disadvantages of germanium in comparison with silicon.
Furthermore germanium dioxide is used in algaculture
as an inhibitor of unwanted diatom
growth in algal cultures since a contamination with the comparatively fast-growing diatoms often inhibits the growth of or outcompetes the original algae strains. GeO2 is readily taken up by diatoms and leads to silicon being substituted by germanium in biochemical processes within the diatoms, causing a significant reduction of the diatoms' growth rate or even a complete elimination of the contaminating algae practically without affecting non-diatom algal species. For this application the typically used concentration of germanium dioxide in the culture medium is between 1 and 10 mg/l, depending on the stage of the contamination and the species.
.
Germanium dioxide is used as a germanium supplement in some questionable dietary supplement
s and "miracle cures". High doses of these resulted in several cases of germanium poisonings.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
, an 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....
of germanium
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....
. Its chemical formula is Ge
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....
O
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
2. Other names include germanic acid, G-15, and ACC10380. It forms as a passivation layer on pure germanium in contact with atmospheric oxygen.
Structure
The forms of germanium dioxide to an extent parallel those of silicon dioxide. Hexagonal GeO2 has the same structure as β-quartz (germanium having coordination numberCoordination number
In chemistry and crystallography, the coordination number of a central atom in a molecule or crystal is the number of its nearest neighbours. This number is determined somewhat differently for molecules and for crystals....
4);
tetragonal GeO2 (the mineral argutite
Argutite
Argutite is a rare germanium oxide mineral. It is a member of the rutile group.It was first described for an occurrence in the Argut deposit, central Pyrenees, Haute-Garonne, France in 1983. The type locality is within a zinc ore deposit within lower Paleozoic sedimentary rocks that have...
) has the rutile
Rutile
Rutile is a mineral composed primarily of titanium dioxide, TiO2.Rutile is the most common natural form of TiO2. Two rarer polymorphs of TiO2 are known:...
-like structure of stishovite
Stishovite
Stishovite is an extremely hard, dense tetragonal form of silicon dioxide. It was long considered the hardest known oxide; however, boron suboxide has recently been discovered to be much harder...
(germanium having coordination number 6); and amorphous (glassy) GeO2 is similar to fused silica.
Germanium dioxide can be prepared in both crystalline and amorphous forms. At ambient pressure the amorphous structure is formed by a network of GeO4 tetrahedra. At elevated pressure up to approximately 9 GPa the germanium average coordination number
Coordination number
In chemistry and crystallography, the coordination number of a central atom in a molecule or crystal is the number of its nearest neighbours. This number is determined somewhat differently for molecules and for crystals....
steadily increases from 4 to around 5 with a corresponding increase in the Ge-O bond distance. At higher pressures, up to approximately 15 GPa, the germanium coordination number
Coordination number
In chemistry and crystallography, the coordination number of a central atom in a molecule or crystal is the number of its nearest neighbours. This number is determined somewhat differently for molecules and for crystals....
increases to 6 and the dense network structure is composed of GeO6 octahedra. When the pressure is subsequently reduced, the structure reverts back to the tetrahedral form. At high pressure, the rutile form converts to an orthorhombic CaCl2 form.
Reactions
Heating germanium dioxide with powdered germaniumGermanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....
at 1000 °C forms germanium monoxide
Germanium monoxide
Germanium monoxide, GeO, is a chemical compound of germanium and oxygen. It can be prepared as a yellow sublimate at 1000°C by reacting GeO2 with Ge metal. The yellow sublimate turns brown on heating at 650°C.. GeO is not well characterised...
(GeO).
The rutile form of germanium dioxide is more soluble than the hexagonal form and dissolves to form germanic acid, H4GeO4 or Ge(OH)4. GeO2 is only slightly soluble in acid but dissolves more readily in alkali to give germanates.
Germanium dioxide is not flammable. In contact with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
, it releases the volatile and corrosive germanium tetrachloride
Germanium tetrachloride
Germanium tetrachloride is a colourless liquid used as an intermediate in the production of purified germanium metal. In recent years, GeCl4 usage has increased substantially due to its use as a reagent for fiber optic production.-Production:...
.
Uses
The refractive indexRefractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
(1.7) of germanium dioxide and optical dispersion properties makes it useful as an optical material for wide-angle lens
Wide-angle lens
From a design perspective, a wide angle lens is one that projects a substantially larger image circle than would be typical for a standard design lens of the same focal length; this enables either large tilt & shift movements with a view camera, or lenses with wide fields of view.More informally,...
es and in optical microscope
Optical microscope
The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly designed in their present compound form in the...
objective
Objective (optics)
In an optical instrument, the objective is the optical element that gathers light from the object being observed and focuses the light rays to produce a real image. Objectives can be single lenses or mirrors, or combinations of several optical elements. They are used in microscopes, telescopes,...
lenses
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
. It is transparent in infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
.
A mixture of silicon dioxide and germanium dioxide ("silica-germania") is used as an optical material for optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
s and optical waveguides. Controlling the ratio of the elements allows precise control of refractive index. Silica-germania glasses have lower viscosity and higher refractive index than pure silica. Germania replaced titania
Titanium dioxide
Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...
as the silica dopant for silica fiber, eliminating the need for subsequent heat treatment, which made the fibers brittle.
Germanium dioxide is also used as a catalyst in production of polyethylene terephthalate
Polyethylene terephthalate
Polyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...
resin, and for production of other germanium compounds. It is used as a feedstock for production of some 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...
s and semiconductor materials.
In the manufacture of integrated circuits and transistors, germanium dioxide is a rather poor dielectric and is chemically unstable, which is one of the disadvantages of germanium in comparison with silicon.
Furthermore germanium dioxide is used in algaculture
Algaculture
Algaculture is a form of aquaculture involving the farming of species of algae.The majority of algae that are intentionally cultivated fall into the category of microalgae...
as an inhibitor of unwanted diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
growth in algal cultures since a contamination with the comparatively fast-growing diatoms often inhibits the growth of or outcompetes the original algae strains. GeO2 is readily taken up by diatoms and leads to silicon being substituted by germanium in biochemical processes within the diatoms, causing a significant reduction of the diatoms' growth rate or even a complete elimination of the contaminating algae practically without affecting non-diatom algal species. For this application the typically used concentration of germanium dioxide in the culture medium is between 1 and 10 mg/l, depending on the stage of the contamination and the species.
Toxicity and medical
Germanium dioxide has low toxicity, but in higher doses it is nephrotoxicNephrotoxicity
Nephrotoxicity is a poisonous effect of some substances, both toxic chemicals and medication, on the kidneys. There are various forms of toxicity. Nephrotoxicity should not be confused with the fact that some medications have a predominantly renal excretion and need their dose adjusted for the...
.
Germanium dioxide is used as a germanium supplement in some questionable dietary supplement
Dietary supplement
A dietary supplement, also known as food supplement or nutritional supplement, is a preparation intended to supplement the diet and provide nutrients, such as vitamins, minerals, fiber, fatty acids, or amino acids, that may be missing or may not be consumed in sufficient quantities in a person's diet...
s and "miracle cures". High doses of these resulted in several cases of germanium poisonings.