Thermal Decomposition of Gadolinium(III) Oxalate

Abstract

The thermal decomposition of gadolinium (III) oxalate decahydrate, Gd2(C_2CO^2-)30 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 (Fig.1, 2):
Evolved gases are water vapor, carbon monoxide and carbon dioxide. Oxygen is consumed by the oxidation of carbon monoxide and deposited carbon in air. Carbon is markedly deposited in inert gases. In carbon dioxide the carbonate oxide is extremely stable, so that it decomposes at higher temperatures than in other gases.
The intermediates, Gd2(CO₃)3 and Gd2O₂.CO₂, reported by others are not detected.
From above results, the decomposition process of the oxalate is discussed, and a mechanism is proposed for the deposition of carbon.