Lanthanum oxide sulfurization in ammonium rhodanide vapor

We have studied phase formation processes in the La-O-S system during La 2 O 3 sulfurization in ammonium rhodanide vapor and identified the sequence of steps in lanthanum oxide conversion into oxysulfides and lanthanum sulfide using X-ray diffraction, IR absorption spectroscopy, and Raman spectroscopy. In the initial stage of the sulfurization process, we observed the formation of lanthanum dioxydisulfide, which converted into lanthanum dioxymonosulfide and lanthanum sesquisulfide during further sulfurization. Our results demonstrate that low structural perfection of lanthanum oxide allows reactive sulfur to penetrate the surface layer, which probably favors lanthanum dioxydisulfide formation.