SCHEDULED MAINTENANCE
Solid-state miscibility gap and thermodynamics of the system BaO–SrO
Abstract
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: ΔGE=x(1–x){33 390–7.09Tx+(29 340–6.237T)(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.
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