Ferroelectric Phase Transitions in Non-Stoichiometric Sodium-Bismuth Titanate Ceramics

Features are studied of the phase formation, structural parameters, microstructure, and dielectric and ferroelectric properties of non-stoichiometric (Na_{0.5 + x}Bi_0.5)TiO₃ ceramics with x = 0–0.1. The investigated samples exhibit ferroelectric phase-transition behavior as anomalies and peaks in dielectric permittivity near 400 and 600 K, respectively. Study of the second harmonic generation shows that phase transitions near 400 K exhibit relaxor-type behavior, indicating there are polar regions in the nonpolar matrix. An increase in the Na/Bi ratio in the initial compositions improves the dielectric and ferroelectric properties of the ceramics.