Thermal Decomposition of Gadolinium(III) Carbonate

Abstract

The thermal decomposition of gadolinium(M) carbonate trihydrate, Gd2(CO₃)3.3 H₂O, has been studied by thermogravimetry (TG), differential thermal analysis (DTA), evolved gas analysis (EGA), infrared absorption spectrometry and X-ray diffraction analysis. The results indicate that the decomposition proceeds basically by the following steps in atmospheres of air, carbon dioxide and inert gases such as nitrogen, argon and helium:
The intermediates, Gd2O^2-2.5 CO₂ and Gd2O^2-. CO, are particularly stable in carbon dioxide.
Evolved gases are water vapor and carbon dioxide, and all detectable reactions are endothermic. The outgassing process of carbon dioxide is complicated, suggesting the existence of some metastable steps. The carbonate oxide obtained under various conditions are not always iden- tical with respect to the crystal structure and the decomposition behavior. Further, the decomposition temperature of Gd2(CO₃)3 is lower than that of Gd2(C₂O₂)3, so that the formation of Gd2 (CO₃)3 is not confirmed in the decomposition of the oxalate.