Gadolinium oxysulfide ( Gd₂ O₂ S), also called gadolinium sulfoxylate, GOS or Gadox, is an

inorganic An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''. Inor ...

compound, a mixed

oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

gadolinium Gadolinium is a chemical element; it has Symbol (chemistry), symbol Gd and atomic number 64. It is a silvery-white metal when oxidation is removed. Gadolinium is a malleable and ductile rare-earth element. It reacts with atmospheric oxygen or moi ...

Uses

The main use of gadolinium oxysulfide is in ceramic

scintillator A scintillator ( ) is a material that 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. re-emit the ab ...

s. Scintillators are used in

radiation detector In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify ionizing particles, such as those produced by nucl ...

s 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 (7.32 g/cm³) and an average grain size ranging from 5 micrometers to 50 micrometers in dependence with the fabrication procedure. 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 In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fl ...

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phe ...

method and the

sulfite Sulfites or sulphites are compounds that contain the sulfite ion (systematic name: sulfate(IV) ion), . The sulfite ion is the conjugate base of bisulfite. Although its acid (sulfurous acid) is elusive, its salts are widely used. Sulfites are ...

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

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 An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

damage to the sample.

Terbium Terbium is a chemical element; it has Symbol (chemistry), symbol Tb and atomic number 65. It is a silvery-white, rare earth element, rare earth metal that is malleable and ductile. The ninth member of the lanthanide series, terbium is a fairly ele ...

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gadolinium oxysulfide is frequently used as a

for

x-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

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 A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or ...

in projection CRTs, though its drawback is marked lowering of efficiency at higher temperature

Variants include, for example, using

praseodymium Praseodymium is a chemical element; it has symbol Pr and atomic number 59. It is the third member of the lanthanide series and is considered one of the rare-earth metals. It is a soft, silvery, malleable and ductile metal, valued for its magnetic ...

instead of terbium ( CAS registry number 68609-42-7, EINECS number 271-826-9), or using a mixture of

dysprosium Dysprosium is a chemical element; it has symbol Dy and atomic number 66. It is a rare-earth element in the lanthanide series with a metallic silver luster. Dysprosium is never found in nature as a free element, though, like other lanthanides, it ...

and terbium for doping (CAS number 68609-40-5, EINECS number 271-824-8). Gadolinium oxysulfide is a promising luminescent host material, because of its high density (7.32 g/cm³) and high effective atomic number of Gd. These characteristics lead to a high interaction probability 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 An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloi ...

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 (space group number 164). 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.Gadolinium Oxysulfide; MSDS nline R.H. Mangels: Hackettstown, NJ, March 15, 1997. http://www.nonius.nl/manualspdf/msdsGadolinumOxysulfide.pdf (accessed October 17, 2011)

References

{{Sulfur compounds Gadolinium compounds Oxides Sulfides Phosphors and scintillators Mixed anion compounds