Influences of processing temperatures on the nature of polarization phenomena in 85% (Bi_0.5Na_0.5)TiO₃-15%BaTiO₃ with different strategies of bismuth oxide non-stoichiometry

Adding excessive metal oxide doping to a powder batch is a known way to compensate for the loss of volatile cation species during high temperature sintering. An important case in the piezoelectric ceramics is the bismuth oxide in the lead-free ferroelectric ceramic bismuth sodium titanate (BNT). Building from the earlier knowledge about excessive bismuth oxide's influences on the properties of BNT, we further note that varying the sintering temperature can both control the distribution of excessive Bi³⁺ and impact the relaxor/normal ferroelectric behaviors and corresponding phase transition. In addition to the nature of polarization, the sintering temperature also significantly manipulates the electrical conductivity. A hypothetical mechanism for the resistive grain boundary is proposed, based on inferences from electrical—microstructure—processing relations in 85% Bi_0.5Na_0.5TiO₃-15% BaTiO₃ with batched Bi₂O₃ excess and acceptor Mg²⁺ in a co-doped strategy.