Effects of texture on microstructure, Raman vibration, and ferroelectric properties in 92.5%(Bi0.5Na0.5)TiO3-7.5%BaTiO3 ceramics

Structure, polarization, dielectric and piezoelectric properties were studied as functions of electric (E) field and temperature in the textured 92.5%(Bi0.5Na0.5)TiO3-7.5%BaTiO3 (BNT-7.5BT) ceramics. The textured BNT-7.5BT ceramics display a high (h 0 0) texture degree up to 0.735 and a coexistence of tetragonal (P4mm + P4bm) phases. The enhanced d33, E-field induced strain, and polarization responses in textured BNT-7.5BT are attributed to the E field induced lattice distortion. High-resolution synchrotron XRD and Raman spectra show a significant phase transition sequence of tetragonal (P4mm + P4bm) → tetragonal (P4bm) → cubic upon heating. The poled specimen displays a long-range-ordered character below depolarization temperature (Td), above which a phase transition takes place from ferroelectric state to relaxor state (TF-R). Compared with Td ∼ 90 °C in the randomly oriented BNT-7.5BT ceramic, the textured BNT-7.5BT ceramic shows a higher Td ∼ 140 °C. This work suggests that the texture technique can promote structural thermal stability of long-range-ordered ferroelectric state.