Melting behaviour of oxide systems for heterogeneous transmutation of actinides. III. The system Am–Mg–O

Publisher Summary This chapter presents the phase diagrams and thermodynamic data for selected cuprates of alkaline-earth (A) and rare-earth (R) elements except Sc, along with the binary to quintenary oxides, and relevant solid-solution series with other elements. Short information on crystal structure is listed for each phase giving it its identity, as well as the concise chemical information which defines its character. The chemistry of phases is illustrated in mostly subsolidus isothermal phase diagrams, drawn after original sources, and referring to diverse chemical conditions defined by partial pressures of oxygen in particular. Reactivity towards CO2 and formation of oxide carbonates are treated systematically as well, having been one of the major experimental obstacles in pursuit of data relevant to pure oxides. The chapter also discusses the essential thermodynamic data for evaluations of phase equilibria appear in the form of entropies and enthalpies at standard and phase-transition temperatures together with heat-capacity functions. Other possibilities are temperature polynomials for standard Gibbs energies of formation or for partial pressures of gaseous components.

Chapter 190 Phase diagrams and thermodynamic properties

Equations correlating the standard enthalpy of formation, the standard entropy and the heat capacity of the oxygen non-stoichiometric compound YBa2Cu3O7-x with the oxygen contents have been derived based on equilibrium thermogravimetric data from the literature. The results show that the oxygen content exhibits a marked influence upon the thermochemical data. The derived equations correlating the enthalpy are in good agreement with the calorimetric results from the literature.

Xinmin Chen

Papers

Correlating thermochemical data of the oxygen non-stoichiometric compound YBa2Cu3O7 –x with the oxygen content