Simultaneous enhancement of piezoelectric properties and Curie temperature in BiFeO3–BaTiO3 lead-free ferroelectrics via simple B-site modification

Abstract

It is necessary to balance the piezoelectric constant (d₃₃) and Curie temperature (T_c) of BiFeO₃–BaTiO₃-based lead-free ceramics. In this work, B-site ion substituted 0.7BiFe_(1−x)Co_xO₃–0.3BaTiO₃ (BFC_x–BT) ceramics were successfully prepared. The values of d₃₃ and T_c were both enhanced from 165 pC/N and 455 °C (x = 0.00) to 191 pC/N and 482 °C (x = 0.004), respectively. The effects of the phase/domain structure and defects on the electrical properties of BFC_x–BT were systematically studied. It is found that the lattice distortion is increased after introducing Co ions, which can be confirmed by the reinforcement of oxygen octahedron torsion. The evolution of the domain structure reveals that appropriate Co substitution could facilitate domain switching due to reduced oxygen vacancies and suppressed leakage currents. These results contribute to the improved T_c and d₃₃. Moreover, the in situ electromechanical coupling properties show that BFC_0.004–BT has a high depolarization temperature (T_d ∼ 470 °C), which ensures the temperature stability of piezoelectric properties.