Measurement of oxygen potential of (U0.8Pu0.2)O2±x at 1773 and 1873 K, and its analysis based on point defect chemistry

Oxygen potential, G¯O2, of (U0.8Pu0.2) O2±x was measured at 1773 and 1873 K by a gas equilibrium method using a thermogravimeter. The measurement data were analyzed based on point defect chemistry, and the partial Gibbs energies at stoichiometric composition were determined from the analysis results which were obtained by using the relationship between deviation of stoichiometric composition x and oxygen partial pressure PO2, x∝PO2±1/2, in the near stoichiometric region. The G¯O2 was represented as functions of the deviation x and temperature, being the calculation results in good agreement with experimental data. The G¯O2 at stoichiometric composition was described by the equation: G¯O2(J/mol)=−517.5×103+116.5⋅T.