抄録
The thermal decomposition of praseodymium oxalate decahydrate, Pr2(C2O4)3·10H2O, was studied in atmospheres of He+O2, He and CO2 by a multiple technique of simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) coupled with evolved gas analysis (EGA). The decomposition proceeded basically by the following steps in all the atmospheres:
Pr2(C2O4)3·10H2O→Pr2(C2O4)3→Pr2O(CO3)2→Pr2O2CO3→Pr oxide,
yielding Pr7O12 in (4:1) He+O2 mixture, and Pr2O3 in He and in CO2 as end products. In CO2 atmosphere, the decomposition of anhydrous oxalate took place at higher temperatures than in other atmospheres owing to the stabilization of intermediate carbonates. All the DTA peaks were endothermic in He and in CO2, whereas exothermic peaks were also detected in He+O2 probably due to the oxidation of CO and deposited carbon, and the disproportionation of CO. In inert atmospheres, finely divided carbon particles were markedly deposited, and then reacted with CO2 which was evolved during the decomposition of Pr2O2CO3. Instead of the disproportionation of CO, the direct formation of carbon and CO2 from Pr2O(CO3)2 was proposed as a possible mechanism for the deposition of carbon particles.
