Estimation of Solid Solubility Curves by the Assumption of Regular Solution (Part 2) -Ternary Systems of Isomorphous Oxides-

Abstract

Binodal solid-solubility curves of ternary isomorphous oxide systems were estimated by the assumption of the regular solution. For the ternary system in which only pairs of components, 1-3 and 2-3, form continuous series of solid solutions, s 1 and s 2 respectively, it was assumed that the tie-lines were parallel to the side 1-2 (Fig.1). Then, the solubility of the binary system of s1(x₃)-s2 (x₃) was obtained by the equal tangents method through the calculation of Gibbs energy of mixing, ΔmG (x₂, x₃) = ΔmH* ( x₂, x₃) T ΔmS^id( x₂, x₃), where ΔmS^id is the entropy of ideal mixing of a ternary system, and ΔmH* is the enthalpy of mixing of s (x₃)2(x₃) binary system. The values of TΔmH* were calculated by applying the emp irical formula. Good agreement between estimated solubilities and experimental binoda l curves was found for the ternary systems of Al₂O₃-Fe₂O₃-Cr₂O₃ (1520 K) and CaTiO₃-BaTiO₃-SrTiO₃(1530 and 1700 K), for which experimental data had been available.