Unveiling the Mechanisms of Oxide Ion Conduction in Nanbo3-Based Ceramics

Abstract

Sodium niobate based ceramics have been comprehensively researched for many years due to fine antiferroelectric properties. Generally, the charge carrier of sodium niobate is mainly electron or hole. Interestingly, our group recently evidenced that A-site bismuth doping could converted it to be pure oxygen ion conductor and the samples showed superior ionic conductivity at intermediate-temperature range. In this paper, the physical mechanisms responsible for oxygen ion conduction were discussed in detail. It is clarified that oxygen vacancies induced by bismuth and sodium evaporation act as oxide ion migration path. Meanwhile, high polarization of bismuth, microstructure and defect complexes have significant effects on oxide ion conductivity in bismuth doping sodium niobate. Combining dielectric loss and coupling theory analysis were given to obtain the migration energy of individual oxide ion between oxygen vacancies. Moreover, the ionic conductivity was slightly improved by Mg/Fe doping at B-site based on the enhancement of oxygen vacancy concentration.

Keywords: Sodium niobate, Oxygen ion coductor, Defect engineering, Activation energy