The evolution of phase structure, dielectric, strain, and energy storage density of complex-ions (Sr1/3Nb2/3)4+ doped 0.82Bi0.5Na0.5TiO3-0.18Bi0.5K0.5TiO3 ceramics

Abstract

Lead-free Bi0.5(Na0.82K0.18)0.5Ti1-x(Sr1/3Nb2/3)xO3 (abbreviated as BNKT-xSN, x = 0.02–0.045) ceramics were fabricated via the conventional ceramic process, and the (Sr1/3Nb2/3)4+ complex-ions were used to modify the phase transition and multifarious electrical responses of BNKT-xSN ceramics. The SN complex-ions absolutely incorporate into the lattice of BNKT matrix to form perovskite structure. The grain morphologies and size are almost unaffected by SN complex-ions. The phase transition concerning ferroelectric type transforming into ergodic relaxor happens with increasing SN content, and the corresponding critical point is x = 0.035. The phase transformation process results in the improvement of energy storage density (W = 0.754 J/cm3) at 80 kV/cm and a high bipolar strain (S = 0.25%) with small hysteresis. The dielectric constant at Tm peaks gradually decreases with increasing SN content, and the ferroelectric-relaxor transition temperature (TF-R) is depressed to room temperature. The evolution behaviors might facilitate our cognition about the mechanism between phase structure and multiple electrical properties of BNT-based ceramics.