Effect of atmospheric composition on the phase formation in the Ba-Bi-O system

The phase formation in the Ba-Bi-O system is significantly affected by oxygen pressure during its synthesis. The reason for the sensitivity of this system to oxygen pressure consists in mobile coexistence of bismuth ions in different oxidation states in the same oxide (Bi⁵⁺ and Bi³⁺, Bi³⁺ and Bi²⁺, etc.). This circumstance determines the oxide structure type and the ability to formation of structural subtypes, i.e., oxides of an isostructural homologous series. The presence of bismuth ions in different oxidation states in the same oxide determines the variety of properties of both bismuth oxides and complex oxides on their basis (ferroelectric, semiconducting, superconducting, and other properties).