PuCrO$_3$ compound synthesis, structural and thermodynamic studies
Abstract
The synthesis of PuCrO$_3$ compound starting from metallic and/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% H$_2$ + 850 ppm H$_2$O). The structure of the polycrystalline perovskite compound PuCrO$_3$ was investigated by means of an X ray powder pattern fitting. A Rietveld analysis was performed using the computer program JANA2000. PuCrO$_3$ crystallizes in the orthorhombic space group Pbnm with a = 549.58(3) pm, b = 771.99(3) pm and c = 543.97(3) pm. 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 PuCrO$_3$ have been calculated from the measured heat capacity and estimated data as a function of temperature.
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