Effects of dopant on the dielectric properties of CaZrO₃ ceramic sintered in a reducing atmosphere

In this study, the influence of CaZrO₃ doped with three dopants, SiO₂, MnO, and Nb₂O₅, and then sintered in a reducing atmosphere on microstructure, phase formation, and electrical properties is investigated. SiO₂ plays the role of sintering aid to enhance the density of CaZrO₃ leading to better performance of electrical properties as a function of SiO₂ content. MnO, and Nb ₂O₅ were incorporated into the Zr-site of CaZrO ₃ to make stoichometric CaZrO₃ into non-stoichiometric CaZrO₃ with Zr excess resulting in the formation of a second phase, CaZr₄O₉, which has a lower dielectric constant (13) in comparison with that of the main phase of CaZrO₃ (32). Thus, the dielectric constant of CaZrO₃ doped with Nb₂O₅, or MnO is decreased markedly. In addition, Mn⁺² incorporated into Zr-sites of CaZrO₃ plays the role of acceptor, which compensates for the number of conduction electrons and contributes to better performance of electrical properties such as insulation resistance and tan δ. Conversely, Nb⁺⁵ incorporated into Zr-sites of CaZrO₃ plays the role of donor and provides more conduction electrons, leading to poor performance of electrical properties.