Preparation and electrical properties of Al and Te co-doped BNT-BKT ceramics

Abstract

0.8Bi_0.5Na_0.5TiO₃(BNT)–0.2Bi_0.5K_0.5TiO₃(BKT) ceramics co-doped with Al₂O₃ and TeO₂ (BNT-BKT-xAT) were prepared using conventional solid-state-reaction method. X-ray diffraction (XRD) analysis of samples with doping concentrations x ≤ 0.10 confirmed a pure perovskite phase, with relative densities over 95%. The sample with x = 0.05 exhibited better dielectric, ferroelectric and piezoelectric performances, i.e., a dielectric constant of 4900 at 1 kHz, a coercive electric field (E_c) of 42.8 kV/cm, remanent polarization (P_r) of 31.8 µC/cm², saturation polarization (P_s) of 45.8 µC/cm², and a piezoelectric coefficient (d₃₃) of 160 pC/N. Increasing the doping concentration resulted in a rise in the phase transition temperature. Moreover, at a higher doping level (x = 0.16), the samples exhibited semiconducting behavior, i.e., a temperature-dependent electrical resistivity. These findings indicate that such Al/Te co-doped BNT-BNT ceramics, particularly with x = 0.05 and x = 0.16, are promising candidates for piezoelectric and temperature sensing applications.