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 show considerable solid‐solution ranges. At least two phases—δ‐Bi 2 O 3 and the rhombohedral β‐phase—are good oxygen‐ion conductors. Most of the phases are confined to the Bi 2 O 3 ‐SrO line at ambient oxygen partial pressure; however, in the SrO‐rich portion, there are at least two phases with oxygen in excess, i.e., with bismuth in the oxidation state Bi 5+ instead of the usual Bi 3+ . There are rather large differences between different experimental data sets; nevertheless, a reasonably consistent set of data can be chosen for the optimization.