Delayed thermal depolarization of Bi0.5Na0.5TiO3-BaTiO3 by doping acceptor Zn2+ with large ionic polarizability

In this paper, (Bi0.5Na0.5)0.94Ba0.06Ti1-xZnxO3 ceramics (0 ≤ x ≤ 0.06) were prepared by the solid oxide reaction route. The doping of Zn2+ into Bi0.5Na0.5TiO3-6BaTiO3 delays the crossover from nonergodic to ergodic states, and the thermal depolarization temperature T d is delayed from 85 °C for pure samples to 120 °C for samples doped by 6% Zn2+, as confirmed by temperature-dependent dielectric and ferroelectric measurements. It suggests that the variation of the T d could be ascribed to the reformation of the long-range ferroelectric order due to the large ionic polarizability of Zn2+. The high ionic polarizability of Zn2+ can result in a large dipole moment of BO6 octahedra, thus strengthening the coherence of neighboring dipoles and suppressing the ferroelectric–relaxor transition. These results improve our understanding on the thermal depolarization of Bi0.5Na0.5TiO3-based ferroelectrics.