Thermally stable large strain in low‐loss (Na 0.2 K 0.8 )NbO 3 ‐BaZrO 3 for multilayer actuators

CuO‐doped (1–x)(Na 0.2 K 0.8 )NbO 3 ‐xBaZrO 3 ceramics (0.0 ≤ x ≤ 0.06) were densified at 960°C. The ceramic with x = 0 exhibited a large sprout‐shaped strain vs electric‐field ( S‐E ) curve and a double polarization vs electric‐field ( P‐E ) hysteresis curve, owing to the defect polarization ( P D ) developed between Cu 2+ ions at Nb 5+ sites and oxygen vacancies. The sizes of the S‐E and P‐E loops decreased with increasing x, owing to the decrease in the number of P D s. The ceramic with x = 0.04 displayed small S‐E and P‐E curves, indicating its small dielectric loss. It exhibited large strain (0.19% at 8.0 kV/mm) at room temperature, which was maintained at 200°C. A similar strain was observed after applying 10 6 cycles of an electric field (3.0 kV/mm). Hence, this specimen exhibited large strain with excellent thermal and fatigue properties. Moreover, the synthesized multilayer actuator using the ceramic with x = 0.04 showed excellent vibrational properties, making it promising for applications in multilayer piezoelectric actuators.