Wikipedia
Barium sulfide
Barium sulfide is the inorganic compound with the formula Ba S. BaS is an important precursor to other barium compounds including BaCO and the pigment lithopone, ZnS/BaSO. Like other chalcogenides of the alkaline earth metals, BaS is a short wavelength emitters for electronic displays. It is colorless, although like many sulfides, it is commonly obtained in impure colored forms.