Gadolinium oxysulfide also called gadolinium sulfoxylate or GOS, is an inorganic compound, a mixed 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....

-sulfide

Sulfide

A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :...

 of 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...

. Its CAS number is .

Uses

The main use of gadolinium oxysulfide is in ceramic scintillators. Scintillators are used in radiation detectors for medical diagnostics. The scintillator is the primary radiation sensor that emits light when struck by high energy photons. Gd₂O₂S based ceramics exhibit final densities of 99.7% to 99.99% of the theoretical density (7.32g/cm3) and an average grain size ranging from 5 micrometers to 50 micrometers in dependence with the fabrication procedure. Terbium-activated gadolinium oxysulfide is frequently used as a scintillator for x-ray imaging. It emits wavelengths between 382-622 nm, though the primary emission peak is at 545 nm. Two powder preparation routes have been successful for synthesizing Gd₂O₂S: Pr, Ce, F powder complexes for the ceramic scintillators. These preparations routes are called the halide flux method and the sulfite precipitation method. The scintillation properties of Gd₂O₂S: Pr, Ce, F complexes demonstrate that this scintillator is promising for imaging applications. There are two main disadvantages to this scintillator; one being the hexagonal crystal structure, which emits only optical translucency and low external light collection at the photodiode. The other disadvantage is the high X-ray damage to the sample.

Terbium

Terbium

Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white rare earth metal that is malleable, ductile and soft enough to be cut with a knife...

-activated

Activator (phosphor)

In phosphors and scintillators, the activator is the element added as dopant to the crystal of the material to create desired type of nonhomogeneities....

 gadolinium oxysulfide is frequently used as a scintillator

Scintillator

A scintillator is a special material, which exhibits scintillation—the property of luminescence when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate, i.e., reemit the absorbed energy in the form of light...

 for x-ray

X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

 imaging. It emits wavelengths between 382-622 nm, though the primary emission peak is at 545 nm. It is also used as a green 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...

 in projection CRTs

Cathode ray tube

The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

, though its drawback is marked lowering of efficiency at higher temperatures.http://www.freepatentsonline.com/5115306.htmlVariants include, for example, using praseodymium

Praseodymium

Praseodymium is a chemical element that has the symbol Pr and atomic number 59. Praseodymium is a soft, silvery, malleable and ductile metal in the lanthanide group. It is too reactive to be found in native form, and when artificially prepared, it slowly develops a green oxide coating.The element...

 instead of terbium (CAS registry number

CAS registry number

CAS Registry Numbersare unique numerical identifiers assigned by the "Chemical Abstracts Service" toevery chemical described in the...

 , EINECS number 271-826-9), or using a mixture of dysprosium

Dysprosium

Dysprosium is a chemical element with the symbol Dy and atomic number 66. It is a rare earth element with a metallic silver luster. Dysprosium is never found in nature as a free element, though it is found in various minerals, such as xenotime...

 and terbium for doping (CAS number , EINECS number 271-824-8).

Gadolinium oxysulfide is a promising luminescent host material, because of its high density (7.32g/cm3) and high effective atomic number of Gd. These characteristics lead to a high stopping power for X-ray radiation. Several synthesis routes have been developed for processing Gd₂O₂S phosphors, including: solid state reaction method, reduction method, combustion synthesis method, emulsion liquid membrane method, and gas sulfuration method. The solid state reaction method and reduction methods are most commonly used because of their high reliability, low cost, and high luminescent properties. (Gd0.99, Pr0.01)2O2S sub-microphosphors synthesized by homogeneous precipitation method are very promising for a new green emitting material to be applied to the high resolution digital X-ray imaging field Gadolinium oxysulfide powder phosphors are intensively used for conversion of X-rays to visible light in medical X-ray imaging. Gd₂O₂S: Pr based solid state X-ray detectors have been successfully reintroduced to X-ray sampling in medical computed tomography (imaging by sections or sectioning, through the use of any kind of penetrating wave).

Crystal Structure

The crystal structure of gadolinium oxysulfide has trigonal symmetry and the space group with one formula unit per unit cell. Each gadolinium ion is coordinated by four oxygen atoms and three sulfur atoms in a non-inversion symmetric arrangement. The Gd₂O₂S structure is a sulfur layer with double layers of gadolinium and oxygen in between.

Toxicity

An approved respirator should be worn if exposure to dust could occur when working with gadolinium oxysulfide. Inhalation may result in lung injuries. Exposure to gadolinium compounds may cause lung and/or liver damage. Gloves are highly recommended when skin contact is likely. Contact with the skin may cause rash, redness or dermatitis. Gadolinium oxysulfide should be stored away from mineral acids, strong oxidizers and flammable materials. When Gadolinium oxysulfide comes in contact with mineral acids, hydrogen sulfide can be produced