Phenomenological analysis for intrinsic properties of nonstoichiometric BaTiO3

The defect and phase equilibria of nonstoichiometric BaTiO3 have been systematically investigated. Self-consistent data were obtained and successfully modeled analytically with defect reactions taking into account the dependent variables of Ba/Ti ratio, temperature, and oxygen partial pressure (Po2). The compositional dependence of the ferroelectric properties in the solid solution regime was described by the Landau-Devonshire theory allowing the parameters of the theory to be functions of stoichiometry. With this approach, we are able to self-consistently determine the spontaneous polarization, dielectric constant, and energetics of the paraelectric-ferroelectric phase transition of powder samples. This theoretical approach provided a way of predicting the intrinsic properties of nonstoichiometric BaTiO3, which have had no previous complete determination or consideration.