Thermodynamic modelling of the cerium–oxygen system

The published data for the thermochemical properties and phase relationships of the cerium–oxygen system have been critically examined. No major inconsistencies in the experimental database have been found. Thermodynamic model parameters of all phases, i.e., liquid, fcc-Ce, bcc-Ce, A-, H-, and X-Ce₂O_3−x, Ce₃O_5±x (Mn₂O₃-type), CeO_2−x, as well as Ce₁₁O₂₀, Ce₆₂O₁₁₂, Ce₄₀O₇₂, Ce₁₉O₃₄, Ce₉O₁₆, and Ce₇O₁₂ have been derived by the least-squares minimization procedure using Thermo-Calc® software. The models are simple to be compatible with the standard Gibbs energy minimization procedure, but provide enough flexibility to account for the crystal structure, defect chemistry, and thermodynamic properties of phases in the Ce–O system. The backward compatibility of the refined parameters with experimental data has been demonstrated by calculation of phase and property diagrams. The Ce–O phase diagram in the whole range of compositions and at elevated temperature, a complete list of invariant reactions as well as the enthalpy and entropy of formation of Ce_nO_2n −2m phases are presented for the first time.