[en] This paper reports on oxygen and oxidation effects in SrS powder that were investigated in order to improve luminance of SrS-based thin-film electroluminescent devices, XPS analysis revealed that the SrS powder surface was oxidized by the adsorption of water, giving the surface products SrSO₃ and free S. Adsorption of water on the surface proceeded rapidly when exposed to a moist atmosphere, and oxidation of the surface occurred when heated in a nitrogen atmosphere as well as in a vacuum. Higher luminance and a better build-up characteristic in the luminance-voltage curve of the EL cells were obtained through heat-treatment of evaporation sources in an H₂S atmosphere