Enhanced Piezoelectric Properties From the Electric Field-Induced Ferroelectric Transition at the MPB of BiGaO₃-Substitued NaBiTiO₃-BaTiO₃(NBT-BT).

A ternary solid solution of lead-free NaBiTiO-BaTiO and BiGaO (NBT-BT-BG) was prepared using conventional, solid-state synthesis. Compositions were prepared near the morphotropic phase boundary (MPB) of ( 1- x )NBT- x BT, located near x = 0.04 -0.09 , and then systematically substituted with 2-5 mol% BG to investigate the effect of the compositional change on the accompanying properties. Dielectric, ferroelectric (FE), and piezoelectric properties were analyzed and compared for all prepared compositions. The FE to ergodic (ER) relaxor transition temperature ( [Formula: see text]) and the reversible electric field-induced relaxor to FE transition were investigated to determine their effects on the strain response. It was found that the MPB composition of 0.93NBT-0.07BT required the least amount of the tertiary phase, 3 mol% BG, to reach a disordered, ER state while also requiring the largest electric fields to induce an FE phase compared with similarly substituted NBT- x BT samples. This led to a maximum unipolar strain of 0.53% (d = 866 pm/V) for the 0.93NBT-0.07BT-0.04BG composition. The largest strains for each system occurred in compositions that were in the ER region at room temperature. These results demonstrate that the addition of BG most effectively destabilizes the long-range dipole order near the MPB composition of NBT-BT, which results in an enhanced electric field-induced strain.