Structure, dielectric, ferroelectric, and field-induced strain response properties of (Mg1/3Nb2/3)4+ complex-ion modified Bi0.5(Na0.82K0.18)0.5TiO3 lead-free ceramics

In this work, Bi0.5(Na0.82K0.18)0.5Ti1-x(Mg1/3Nb2/3)xO3 (BNKT-xMN) lead-free ceramics with x = 0.02-0.045 were fabricated by conventional solid state reaction sintering method. The effects of MN content on the phase structure, microstructure, dielectric, ferroelectric, energy storage and strain response were investigated. The MN diffuses into the lattice of BNKT matrix and forms solid solution. The MN doping pinches the hysteresis loops, and improves the energy storage density and efficiency. Meanwhile, the electric field-induced strain response with low hysteresis is also promoted. The B-site modification induces the transition from ferroelectric phase to ergodic relaxor. The significant enhancement in energy storage and strain response is attributed to the compositionally induced phase transition. A noticeable diffuse phase transition is confirmed by dielectric analysis. Thus, the energy storage and strain properties of BNKT ceramics can be modified by complex-ion induced phase transition.