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

It is necessary to balance the piezoelectric constant (d(33)) and Curie temperature (Tc) of BiFeO3-BaTiO3-based lead-free ceramics. In this work, B-site ion substituted 0.7BiFe((1-x))CoxO(3)-0.3BaTiO(3) (BFCx-BT) ceramics were successfully prepared. The values of d33 and Tc were both enhanced from 165 pC/N and 455 degrees C (x = 0.00) to 191 pC/N and 482 degrees C (x = 0.004), respectively. The effects of the phase/domain structure and defects on the electrical properties of BFCx-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 Tc and d33. Moreover, the in situ electromechanical coupling properties show that BFC0.004-BT has a high depolarization temperature (T-d similar to 470 degrees C), which ensures the temperature stability of piezoelectric properties.