Thermal Decomposition of Rare Earth Oxysulfides

Abstract

In a dynamic air atmosphere the rare earth oxysulfides are oxidized to oxysulfates between 600 and 900 °C. The oxysul-fate phase is unstable at higher temperatures, however, and decomposes to oxide. The oxidation of the heavier rare earth oxysulfides to oxysulfate occurs only partially before the decomposition to oxide begins.

In an inert atmosphere the oxysulfides are stable up to 1300 °C. In vacuum, Eu³⁺Y₂O₂S is stable up to at least 1000 °C.