Bi2O3

Bi2O3, also known as bismuth(III) oxide, is a dense, pale yellow to white crystalline solid. It is a stable oxide of bismuth and is relatively insoluble in water but dissolves in acids to form bismuth salts. The compound is used as a precursor for other bismuth compounds and as a pigment in some glazes and ceramics.

Bi2O3 exists in several polymorphs that are temperature dependent. The commonly encountered forms include alpha-Bi2O3 (low-temperature, monoclinic), and higher-temperature beta and gamma polymorphs. A high-temperature fluorite-type phase, delta-Bi2O3, exhibits unusually high oxide-ion conductivity. In many applications, the delta phase is stabilized at room temperature by doping with oxides of rare earth elements (for example Y2O3 or Sm2O3), producing a solid solution used as an oxide-ion conductor in solid oxide fuel cells and related electrochemical devices.

Synthesis and preparation typically involve calcination or calcination of bismuth salts or carbonates. Bi2O3 can be produced by heating bismuth-containing precursors such as bismuth nitrate, carbonate, or oxide precursors to high temperatures, driving off water and other volatiles to yield the oxide.

Applications center on its role as a component in catalysts, pigment and glaze formulations, and as a source material for preparing doped bismuth oxides with high oxide-ion conductivity. The doped delta-like phases are especially important in electrochemical devices, while the pure oxide serves in various ceramic and catalytic contexts.

Safety considerations are generally modest; Bi2O3 has relatively low toxicity compared with many heavy metal compounds, but inhalation of dust should be avoided and standard industrial hygiene practices observed.