Bismuth(III) oxide

Bismuth(III) oxide is perhaps the most industrially important compound of bismuth. It is also a common starting point for bismuth chemistry. It is found naturally as the mineral bismite (monoclinic) and sphaerobismoite (tetragonal, much more rare), but it is usually obtained as a by-product of the smelting of copper and lead ores. Bismuth trioxide is commonly used to produce the "Dragon's eggs" effect in fireworks, as a replacement of red lead.

Structure

The structures adopted by Bi₂O₃ differ substantially from those of arsenic(III) oxide, As₂O₃, and antimony(III) oxide, Sb₂O₃.

Bismuth oxide, Bi₂O₃ has five crystallographic polymorphs. The room temperature phase, α-Bi₂O₃ has a monoclinic crystal structure. There are three high temperature phases, a tetragonal β-phase, a body-centred cubic γ-phase, a cubic δ-Bi₂O₃ phase and an ε- phase. The room temperature α-phase has a complex structure with layers of oxygen atoms with layers of bismuth atoms between them. The bismuth atoms are in two different environments which can be described as distorted 6 and 5 coordinate respectively.