Niobates and Tantalates of Tervalent Elements

The types of compounds in the A₂O₃– B₂O₅ systems, where A = the p-, d-, and f-elements of Group III, the p-elements of Group V, and the d-elements of the fourth period in the tervalent state and B = Nb or Ta, are considered. An analysis of the methods of making the niobates and tantalates is given, their structure is described, and their physicochemical and electrophysical properties are reviewed. Special attention has been paid to the description of the rare-earth element meta-niobates, which exhibit the properties of electrets, and of the compounds of composition ABO₄ (A = Sb, Bi; and B = Nb, Ta), which belong to a new group of ferroelectrics. Bibliography of 147 references.