A review of bismuth-rich binary oxides in the systems Bi2O3-Nb2O5, Bi2O3-Ta2O5, Bi2O3-MoO3, and Bi2O3-WO3

Bismuth-rich phases in the Bi2O3-Nb2O5, Bi2O3-Ta2O5, Bi2O3-MoO3 and Bi2O3-WO3 systems have been investigated using synchrotron X-ray diffraction (XRD) and electron diffraction (ED) to resolve outstanding problems concerning phase relationships, unit cells, and symmetry. A temperature-composition phase diagram for the Bi2O3-Nb2O5 system is presented. Single-phase powder specimens have been prepared for most phases. A modulated structure approach has been applied to the characterization of phases, and space groups or superspace groups assigned. The most appropriate description (commensurate modulation, incommensurate modulation or superstructure) for the structure of each of the phases is discussed. (C) 1998 Academic Press.