Large strain with low hysteresis in Bi4Ti3O12 modified Bi1/2(Na0.82K0.18)1/2TiO3 lead-free piezoceramics

In order to obtain BNT-based ceramic system with excellent electric-field-induced strain performance for actuator applications, a novel solid solution (100-x)Bi-1/2(Na0.82K0.12)(1/2)TiO3-xBi(4)Ti(3)O(12) ((100-x)BNKT-xBiT, x = 0-12 wt%) was designed and fabricated by solid state synthesis. The microstructure and related electrical properties of this material were systematically investigated. It was found that BiT is dissolved into the lattice structure of the BNKT, leading to a greater increase in the volatilization of Na and K, thus produce more A-site vacancies compared with the undoped BNKT. The 9 wt%BiT doped sample not only has sufficient A-site vacancies to destroy the long-range ferroelectric order of the base composition but also favors the presence of extremely stable relaxor phase at room temperature. Further, the ferroelectric-to-relaxor phase transition temperature TF-R can be effectively tuned to about 0 degrees C, giving rise to a large signal piezoelectric coefficient d*(33) of 485 pm/V with a small hysteresis eta of 23%.