DEFECT STRUCTURE, ELECTRICAL-PROPERTIES AND TRANSPORT IN BARIUM-TITANATE .2. CONSISTENCY REQUIREMENTS BETWEEN DEFECT MODELS AND CRYSTAL PROPERTIES

The defect disorder of nonstoichiometric compounds is considered in te rms of several crystal properties such as electrical conductivity, the rmo-power, work function and deviation from stoichiometry. Quantitativ e 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(O2) exponent of crystal properties such as el ectrical 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 BaTiO3. It has been concluded that construction of a defect structure model, especially fo r a compound of such complication as BaTiO3, should be based on severa l 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.