Enhanced electric field induced strain in complex-ion Ga3+ and Ta5+-doped 0.93BNT-0.07BT piezoceramic

The 0.93(Bi_0.5Na_0.5)TiO₃-0.07BaTiO₃ doped with different amount of (Ga_0.5Ta_0.5)⁴⁺ complex-ion from 0 to 4 mol% (abbreviated as BNBT-100xGT) ceramics were prepared. Phase analysis revealed that up to x = 0.035, Ga³⁺ and Ta⁵⁺ completely dissolve in BNBT perovskite structure and substitute in B-site. Increase in x more than 0.02 resulted in formation of pinched P-E loops accompanied by sharp decrease in P_r. This observation can be attributed to the phase transition from ferroelectric (FE) to a non-polar ergodic relaxor (ER) which could be transformed reversibly to a FE phase by applying an electric field. According to temperature-dependence dielectric constant results, transition temperature from FE to ER phase decreased and for ceramic with x = 0.03 shifted to lower than room temperature with increasing GT content. As a result, enhanced unipolar electric field-induced strain (0.4% under 60 kV/cm) corresponding to d₃₃^* of 667 pm/V was obtained in this ceramic. The large electrostrain is accompanied with relatively large hysteresis, which should be lowered for actuator applications. However (Ga_0.5Ta_0.5)⁴⁺ complex-ion doping of BNT-based ceramics, could be considered as an efficient approach to enhance electrical properties, especially electrostrain characteristic of these ceramics, as competitive alternatives to lead-based ceramics.