Ionic conductive and dielectric properties of samarium isovalent doping in non-stoichiometric bismuth sodium titanate perovskite

Oxide ion-conducting solid electrolytes are of considerable importance as fuel cell component. Recently, Bi0.5Na0.5TiO3 (BNT)-based perovskite-structured oxides become a new hotspot of solid electrolyte since it has potential in oxygen ion conduction. Considerable ionic conductivity is achieved in a Bi deficient or an acceptor doping composition. In this work, the role of Sm content without lone pair electrons substituted for isovalent Bi is studied on the electrical properties of non-stoichiometric (Bi0.45Ca0.04)Na0.5TiO2.965 (BCNT). In the solid solution range, a transformation from resistive BCNT to dominated oxide ionic conductive process is revealed despite no additional designed vacancies involved. Interestingly, employment of smaller Sm cations by doping favors the plateau formation of dielectric permittivity at higher frequencies. Lone pairs substitution conception and shrinkage of lattice parameters are proposed to be responsible for the anomalous dielectric relaxation.