CuO‐added KNbO3‐BaZrO3 lead‐free piezoelectric ceramics with low loss and large electric field‐induced strain
CuO‐added (1‐x)KNbO3‐x mol%BaZrO3 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 Ds) that formed between Cu2+ 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 Ds 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 106 cycles of 3.0 kV/mm.
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