Cesium iodide

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

Terbium-doped 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.

Variants include, for example, using praseodymium instead of terbium (CAS number, EINECS number 271-826-9), or using a mixture of dysprosium and terbium for doping (CAS number , EINECS number 271-824-8).