Effects of Ba substitution on structure and dielectric response of Bi2Mn4O10 ceramics

Structure and dielectric response in barium substituted manganites Ba0.2Bi1.8Mn4O10 were investigated. The structural refinements showed that Mn3+ and Mn4+ occupy the pyramidal sites and the octahedral sites, respectively. The barium substitution has no distinct effect on the Mn4+–O distance, but significantly increases the Mn3+–O distances. Compared with Bi2Mn4O10, the barium substituted Bi2Mn4O10 showed weaker dielectric responses with two dielectric relaxations at low temperatures (125–200 K) and high temperatures (200–400 K). The increase of Mn3+–O distances weakens the low temperature dielectric relaxation and increases the activation energy. The significant decrease of the mobility of the defect complex composed of oxygen vacancies and conducting charge carriers results in the reduction of the high temperature dielectric response.