A survey of available experimental excess thermodynamic properties for the binary alkaline earth oxide mixtures is given. The known excess thermodynamic properties of the oxide mixtures are evaluated and missing values are estimated by analogy with the binary common-ion alkali halide mixtures. The phase diagrams of the oxide mixtures corresponding to the evaluated / estimated excess properties are calculated and compared with the available experimental phase diagrams.

Binary alkaline earth oxide mixtures: Estimation of the excess thermodynamic properties and calculation of the phase diagrams

The thermodynamic descriptions of the BaO-SrO-TiO2 pseudo-ternary and its lower order sub-systems have been made by critically evaluating all available experimental data. The temperature-dependent Gibbs energies of perovskite structural phases were evaluated to be relative to the standard element reference state (SER). The substitutional solution model for liquid and line compounds, Neumann-Kopp Rule for stoichiometric compounds were adopted. A set of self-consistent parameters reproducing most of the corresponding experimental data has been obtained.

Thermodynamic description of BaO-SrO-TiO2 system

A solid-state miscibility gap in the pseudo-binary system BaO-SrO is delineated by X-ray diffraction studies on samples equilibrated either in vacuum or under flowing inert gas at temperatures between 1073 and 1423 K. For the SrxBa1-xO solid solution an asymmetric phase boundary, characterized by a critical temperature of 1356 (+/-4) K and composition x=0.55 (+/-0.008), is obtained. Thermodynamic mixing properties of the solid solution, derived from the experimental phase boundary compositions and temperatures, can be represented by the expression:
Delta G(E)=x(1-x){33 390-7.09T)x+(29 340-6.23T)(1-x)} J mol(-1)It is necessary to include excess entropy terms to obtain a good fit to the experimental data. The chemical spinodal curve is computed from the thermodynamic parameters

Solid-state miscibility gap and thermodynamics of the system BaO–SrO

In order to provide an adequate basis for extrapolation into higher order oxide systems, a thermodynamic assessment was performed on the BaO-CaO, BaO-SrO, BaO-SiO2 and SrO-SiO2 binary systems by cr ...

R. Chastel

Papers

Determination of the excess molar Gibbs energy of {(1 − x)BaO + xSrO} (s) by means of Knudsen-effusion mass spectrometry