Doped gamma-Bi2O3: synthesis of microcrystalline samples and crystal chemical analysis of structural data

Abstract

A series of microcrystalline products containing the gamma-Bi2O3 phase doped with Co, Fe, Mn, Pb, Sb, Si, Ti, V and Zn has been prepared by solid state reaction. Based on the heating temperature and heating time, the following order of increasing relative stability of the doped gamma-Bi2O3 phases was established: Sb 51 lt Co2+ Mn4+ lt Fe3+ approximate to Si4+ lt Ti4+ lt V5+ lt Zn2+ lt Ph2+. The unit cell parameters of the prepared samples were compared with available structural data, which were also further analyzed concerning the geometrical parameters and overall reliability. The analysis confirmed the socalled Radaev's model for the doped gamma-Bi2O3 structure, which assumes the presence of Bi2(3+) ions slightly displaced from the tetrahedral M site and corresponding vacancies (resulting from a lone pair on Bi2(3+)) in the coordinating oxygen positions. In addition, the analysis suggested that this model can be further improved. The existence of an approximate linear relationship between the unit cell parameters of the doped gamma-Bi2O3 phases and the ionic radii of the M cations was found.