On the Structure of Bismuthsesquioxide: The α, β, γ, and δ-phase

The structures of four polymorphs of Bi2O3 were investigated by means of X-ray and neutron powder diffraction. The position parameters of the oxygen atoms in α-Bi2O3 were refined. High temperature neutron diffraction shows that a complicated disorder exists in the oxygen sublattice of the fluorite related structure of the solid electrolyte δ-Bi2O3. X-ray diffraction data on metastable β-Bi2O3 correspond with a distorted fluorites structure with the voids in the oxygen sublattice ordered in the 〈001〉 direction. X-ray and neutron diffraction data indicate that metastable γ-Bi2O3 is isomorphous to Bi12GeO20.