STRUCTURAL CHEMISTRY AND PHYSICAL-PROPERTIES OF SOME TERNARY OXIDES IN THE BI2O3-TA2O5 SYSTEM

A high-resolution electron microscope has been used in structural investigation of the Bi2O3{single bond}Ta2O5 system. Several distinct phases in the compositional range between Bi2O3 and BiTaO4 have been examined. The β-Bi2O3-related solid solution and the δ-Bi2O3-related type I and type II solid solutions are isomorphous with the analogues in the Bi2O3{single bond}Nb2O5 system. Two monoclinic structures with the compositions of Bi7Ta3O18 (type II*) and Bi4Ta2O11 (type III) are proposed. The composition dependence of the structure transition and the structure dependences of band gaps and thermoelectric power of the materials are discussed. © 1992 Academic Press, Inc. All rights reserved.