Thermal Decomposition of Cerium(III) Acetate Hydrate by a Three-dimensional Thermal Analysis

Abstract

The thermal decomposition of cerium(III) acetate hydrate, Ce(CH₃CO₂)₃·1.5H₂O, in helium was successfully studied by the simultaneous measurement of TG-DTA and EGA by mass spectrometry (TG-DTA-MS) as well as that of X-ray diffractometry: DSC (XRD-DSC). TG-DTA-MS was useful to elucidate the complicated successive reactions accompanying the formation of intermediate products. Crystalline cerium(III) anhydrous acetate appeared at 212°C and transformed to another phase at 286°C. Cerium(III) anhydrous acetate decomposed in the temperature range of 300 - 700°C to cerium(IV) oxide via four decomposition steps; the chemical compositions of the three decomposition intermediate products were presumed to be Ce₂O(CH₃CO₂)₄, Ce₂O₂(CH₃CO₂)₂ and Ce₂O₂CO₃. The endothermic dehydration and the exothermic crystallization were characterized by simultaneous XRD-DSC. It has been demonstrated that cerium(III) changed to cerium(IV) in the final step. A detailed decomposition mechanism of Ce(CH₃CO₂)₃·1.5H₂O is discussed.