THERMODYNAMIC ASSESSMENT OF THE BISMUTH-STRONTIUM-OXYGEN OXIDE SYSTEM

The experimental data on the oxide portion of the Bi-Sr-O system have been reviewed, and an optimized thermodynamic description is presented . There are at least seven stable ternary oxide phases, two of which s how considerable solid-solution ranges. At least two phases-delta-Bi2O 3 and the rhombohedral beta-phase-are good oxygen-ion conductors. Most of the phases are confined to the Bi2O3-SrO line at ambient oxygen pa rtial pressure; however, in the SrO-rich portion, there are at least t wo phases with oxygen in excess, i.e., with bismuth in the oxidation s tate Bi5+ instead of the usual Bi3+. There are rather large difference s between different experimental data sets; nevertheless, a reasonably consistent set of data can be chosen for the optimization.