Large strain response in Li/Nb co-doped Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ lead-free piezoceramics

A series of (Bi_0.5Na_0.4K_0.1)Ti_0.98Nb_0.02O₃-xLi lead-free ceramics were fabricated using the solid-state reaction technique. The effects of Li/Nb cations on the structural and electrical properties of the ceramics were investigated. All the sintered ceramics exhibited pure perovskite structure and the average grain size increased slightly with increasing the Li content. Shape of the P-E loops illustrated the relaxor characteristic of all the samples. A giant strain of 0.4% was obtained at 60 kV/cm at x = 0.01 and the corresponding normalized strain was up to 683 pm/V, moreover, the strain exhibits excellent fatigue-resistance behavior. The giant strain can be attributed to the ferroelectric-relaxor phase transition under external driving electric field. These results indicate the sintered Li/Nb co-doped lead-free ceramics can be promising candidate for actuator applications.