Defect structure, electrical properties and transport in barium titanate. II. Consistency requirements between defect models and crystal properties

Abstract

The defect disorder of nonstoichiometric compounds is considered in terms of several crystal properties such as electrical conductivity, thermo-power, work function and deviation from stoichiometry. Quantitative interrelationships between the properties are considered in terms of their consistency with a particular defect model. The consistency is analysed in terms of a p(O 2) exponent of crystal properties such as electrical conductivity, thermopower, Fermi energy and nonstoichiometry as well as the concentration of electron charge carriers. The analysis is performed for a ternary oxide such as undoped BaTiO 3. It has been concluded that construction of a defect structure model, especially for a compound of such complication as BaTiO 3, should be based on several properties rather than on an individual property. It is argued that defect models based solely on electrical conductivity, which combines both concentration and mobility terms, require a verification by other properties such as thermopower.