Atmosphere controlled conductivity and Maxwell-Wagner relaxation in Bi_0.5K_0.5TiO₃—BiFeO₃ ceramics Available to Purchase

Here, we report on a giant dielectric relaxation in (1 − x)Bi_0.5K_0.5TiO₃—xBiFeO₃ ceramics below ∼300 °C, which becomes more pronounced with increasing BiFeO₃ content. The relaxation was shown to be of Maxwell-Wagner type and associated with charge depletion at the electroded interfaces. It was also shown that the relaxation could be controlled or, eventually, removed by heat treatment in controlled partial pressure of oxygen. This was rationalized by the relationship between the electrical conductivity and variation in the oxidation state of Fe, which is strongly coupled to the partial pressure of oxygen. The results are discussed with emphasis on oxygen diffusion and point defect equilibria involving oxygen vacancies and iron in divalent and tetravalent state. Finally, the barrier-free dielectric properties of the (1 − x)Bi_0.5K_0.5TiO₃—xBiFeO₃ ceramics are reported.