Electric field-induced strain mechanism in multi-cationic quenched fired BiFeO₃-based piezoceramics

Piezoceramic composition (1-z) (0.67Bi_1.05FeO₃–0.33BaTiO₃)–zBi(Mg_0.5Zr_0.5)O₃ (z = 0.00−0.10) were framed in this work. Regular firing technique succeeding by quenching method was applied. Effect of Bi(Mg_0.5Zr_0.5)O₃, abbreviated as BMZ, modification on structural and electrical properties were systematically analyzed. A large-field piezoelectric coefficient (S_max/E_max = d₃₃*) of 560 pm/V at 4 kV/mm and relatively small hysteresis (~ 28%) were obtained. The possible enhancement in strain, d₃₃ and P_r values near the optimal compositions z = 0.060, 0.080 can be ascribed to the augmented anharmonicity of lattice vibrations that may facilitate the flexiblity (at unit cell level) of these narrow compositions and triggers the enrichment of piezoelectric properties. A large piezoactuation constant with relatively low hysteresis loss and high working temperature (T_m around 415 ^οC) without unwanted depolarization temperature T_d made the investigated piezomaterial promising for the ceramic actuators’ applications. Unlike BNT-based systems, where mixed ergodic relaxor (ER) and nonergodic relaxor (NR) states are supposed to generate high strains, in the present BF-based ceramics, based on obtained results, BMZ-modified BF-BT materials are hypothesized to spontaneously switch from a high-temperature ER state to a ferroelectric state without transitioning to an intermediary NR state.