Stability of the Perovskite Compounds in the Ce—Ga—O and Pu—Ga—O Systems.

Cerium oxides are used as surrogates for plutonium oxides because of the similarities in their thermodynamic properties. In this study, the stability limits of both CeGaO3 and PuGaO3 with respect to the partial pressure of oxygen and temperature have been predicted by theoretical calculations. Using the results of the calculations as guidance, mixtures of CeO2 and Ga2O3 have been prepared and thermally treated at 1273, 1473, and 1673 K, in atmosphere of air, argon, or Ar–6% H2. In the samples annealed under low oxygen partial pressures, the CeGaO3 perovskite-type compound was identified. Based on Rietveld structure refinement, the orthorhombic space group (Pnma, 62) was confirmed.