CuO‐added KNbO 3 ‐BaZrO 3 lead‐free piezoelectric ceramics with low loss and large electric field‐induced strain

CuO‐added (1‐ x ) KN bO 3 ‐ x mol%BaZrO 3 ceramics with 0.0≤ x ≤7.0 were sintered at 960°C. Large double polarization vs electric field ( P‐E ) and sprout‐shaped strain vs electric field ( S‐E ) hysteresis curves were obtained from the specimens with x ≤2.0. They exhibited large polarizing electric fields ( E P ) owing to the presence of a large number of defect dipoles ( P D s) that formed between Cu 2+ ions and oxygen vacancies. Small double P‐E hysteresis curves were observed for the specimens with x ≥3.0 with reduced E P because of the decreased number of P D s and the presence of a polymorphic phase structure containing both orthorhombic and pseudocubic structures. In particular, the specimen with x =5.0 exhibited a large strain of 0.16% at 8.0 kV/mm with a small E P of 1.2 kV/mm and good fatigue property: this specimen maintained a strain of 0.13% at 6.0 kV/mm after 10 6 cycles of 3.0 kV/mm.