Novel uses of the thermo-microbalance in the determination of nonstoichiometry in complex oxide systems

Abstract

New uses of the thermo-microbalance are possible when studying complex oxide systems such as PbO-La2O3-ZrO2-TiO2 that incongruently and preferentially vaporize a single component. Several vapor phase equilibration procedures are possible when the microbalance is equipped with constant activity multiphase (CAMP) crucibles designed to provide an equilibrium source of, or sink for, PbO vapor. The compositional range of a compound's single-phase stability can be directly determined at temperature. The ionic substitutional lattice site, ionic valence, and resultant charge compensation mechanism that is associated with the solution of an impurity oxide into A-B-O compounds can be inferred from gravimetric data. The methods are applicable to the controlled sintering of these materials. An expanded version of the Knudsen effusion experiment is discussed whereby extensive information of the thermodynamics, phase equilibria, and nonstoichiometry of the oxide system can be generated by a single gravimetric experiment. The binary PbO-TiO2 system is offered as an illustration.