Thermal decomposition behavior of the rare-earth ammonium sulfate R2(SO4)3·(NH4)2SO4

Rare-earth ammonium sulfate octahydrates of R2(SO4)3·(NH4)2SO4·8H2O (R=Pr, Nd, Sm, and Eu) were synthesized by a wet process, and the stable temperature region for the anhydrous R2(SO4)3·(NH4)2SO4 form was clarified by thermogravimetry/differential thermal analysis, infrared, Raman, and electrical conductivity measurements. Detailed characterization of these double salts demonstrated that the thermal stability of anhydrous R2(SO4)3·(NH4)2SO4 is different between the Pr, Nd salts and the Sm, Eu salts, and the thermal decomposition behavior of these salts was quite different from the previous reports.