CuO‐added KNbO₃‐BaZrO₃ lead‐free piezoelectric ceramics with low loss and large electric field‐induced strain

Abstract

CuO-added (1-x)KNbO 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.

Thermally stable large strain in low‐loss (Na0.2K0.8)NbO3‐BaZrO3for multilayer actuators

“…However, the detailed crystal structures of these specimens could not be identified using normal XRD patterns. 24 The sample with x = 0.06 exhibited only a pseudocubic (220) P reflection ( Figure 2(F)), revealing its pure pseudocubic structure. Therefore, an orthorhombic-pseudocubic PPB structure, in which the orthorhombic and pseudocubic structures coexist, was formed in the sample with x = 0.05.…”

“…24 However, the thermal stability of the CuOdoped KNbO 3 ceramic was low, leading to a small effective strain at 75°C, 24 which hinders the application of CuO-doped KNbO 3 -BaZrO 3 ceramics in piezo actuators. 24 However, the thermal stability of the CuOdoped KNbO 3 ceramic was low, leading to a small effective strain at 75°C, 24 which hinders the application of CuO-doped KNbO 3 -BaZrO 3 ceramics in piezo actuators.…”

Piezoelectric properties of (Na0.5K0.5)(Nb1‐xSbx)O3‐SrTiO3 ceramics with tetragonal‐pseudocubic PPB structure

“…For (Bi,Na)TiO 3 ‐based Pb‐free ceramics, this sprout‐shaped S‐E curve is explained by a phase transition between an ergodic relaxor state and a ferroelectric state upon the application of an electric field . The sprout‐shaped S‐E curve obtained from acceptor‐doped Pb‐free‐piezoelectric ceramics is explained by the presence of a defect polarization induced between the acceptor ions and the oxygen vacancies …”

“…These lead‐free piezoelectric ceramics can be used for piezoelectric actuators. The large strain observed in these ceramics is attributed to the formation of a sprout‐shaped strain vs electric field ( S‐E ) curve without remnant strain . For (Bi,Na)TiO 3 ‐based Pb‐free ceramics, this sprout‐shaped S‐E curve is explained by a phase transition between an ergodic relaxor state and a ferroelectric state upon the application of an electric field .…”

“…Several investigations have been also conducted on (Bi,Na)TiO 3 ‐based and acceptor‐doped Pb‐free piezoelectric ceramics because they showed large electric field‐induced strain . These lead‐free piezoelectric ceramics can be used for piezoelectric actuators.…”