Gadolinium oxysulfide

Gadolinium oxysulfide (Gd₂O₂S), also called gadolinium sulfoxylate, GOS or Gadox, is an inorganic compound, a mixed oxide-sulfide of gadolinium. Its CAS number is 12339-07-0.

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 (7.32 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 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-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. It is also used as a green phosphor in projection CRTs, though its drawback is marked lowering of efficiency at higher temperatures.[1] Variants include, for example, using praseodymium instead of terbium (CAS registry number 68609-42-7, EINECS number 271-826-9), or using a mixture of dysprosium and terbium for doping (CAS number 68609-40-5, EINECS number 271-824-8).