PuCrO3 compound: synthesis, structural and thermodynamic studies

The synthesis of PuCrO3 compound starting from metallic or sesquioxide chromium and PuO2 powder mixtures in stoichiometric ratios has been studied at different temperatures under atmospheres with a varying oxygen potential (Ar, Ar + 5% H2, Ar + 5% H2 + 850 ppm H2O). The structure of the polycrystalline perovskite compound PuCrO3 was investigated by X-ray powder pattern fitting. A Rietveld analysis was performed using the computer program JANA 2000. PuCrO3 crystallizes in the orthorhombic space group Pbnm with a = 543±2 Å, b = 549±2 Å and c = 771±2 Å. A XAS study gave oxidation states +III for both chromium and plutonium. The heat capacity of PuCrO3 was measured by means of a differential scanning calorimeter (DSC) in the temperature range of 373–1373 K. Debye temperature as well as electronic defect energies have been fitted from these measurements. Enthalpy increment, entropy and free energy function of PuCrO3 have been calculated from the measured heat capacity and estimated data as a function of temperature.