Two-step synthesis strategy for long-range ordered and relaxor ferroelectrics to achieve excellent electrical performance and thermal stability in BF-BT-based ceramics

Abstract

Achieving high piezoelectric performance in BiFeO₃–BaTiO₃-based ceramics while enhancing the stability of the piezoelectric coefficient (d₃₃) during depolarization presents a significant challenge. The poor thermal stability stems from intrinsic defects and disruption of the long-range ferroelectric order induced by doping with foreign elements. This study employs a two-step synthesis strategy, combining long-range-ordered ferroelectrics with relaxor ferroelectrics. By modifying the domain-structure characteristics, the energy barrier for switching polar structures is increased, thereby enhancing the thermal stability. This process yields a high d₃₃ value (93 pC N⁻¹) and high depolarization temperature (T_d ≈ 650 °C) while effectively mitigating the continuous decline in d₃₃ observed in relaxor ferroelectrics from room temperature to T_d. After depolarization at 650 °C for 3 hours, the variation in d₃₃ (Δd₃₃/d₃₃) was only 17.2%. The resistivity (ρ) remained high at 1.3 × 10⁶ Ω cm at 300 °C. Ultrasonic experiments based on this piezoelectric material confirmed that at 300 °C, the symmetric (S₀) and antisymmetric (A₀) zero-order modes maintained high signal-to-noise ratios of 21.6 dB and 20.3 dB, respectively. These results highlight the strong potential of the ceramic for high-temperature ultrasonic structural health monitoring (SHM) systems.