Phase Equilibria in the System Barium Titanate—Strontium Titanate

Phase equilibria in the system BaTiO₃–SrTiO₃ (with 0 to 7 mol% SrTiO₃) were studied at temperatures above 1600°C in air. Quenching experiments were performed using high-purity starting materials, and run products were examined by X-ray diffraction and differential scanning calorimetry to determine phase composition and Sr concentration. Melting involves a binary loop intersected by the invariant reaction hexagonal (Ba, Sr)TiO₃( ss ) ⇌ cubic (Ba, Sr)TiO₃( ss ) + liquid. In contrast with earlier work, these results indicate that there is no depression of the melting point with Sr addition and no congruent melting point in this compositional range.