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-degrees-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) half-arrow-right-over-half-arrow-left 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.