Thermally stable large strain in low‐loss (Na0.2K0.8)NbO3‐BaZrO3 for multilayer actuators

• Published in: Journal of the American Ceramic Society 2019-11, Vol.102 (11), p.6837-6849
• Main Authors: Kim, Sun‐Woo, Lee, Tae‐Gon, Kim, Dae‐Hyeon, Kim, Eun‐Ji, Kim, Dae Su, Kang, Woo‐Seok, Jo, Wook, Lee, Sang Jin, Han, Seung Ho, Kang, Hyung‐Won, Hong, Youn‐Woo, Nahm, Sahn
• Format: Article
• Language: English
• Subjects: Barium zirconates; Ceramics; Copper; Dielectric loss; Electric fields; lead‐free ceramics; Materials fatigue; Multilayers; Niobates; Piezoelectric actuators; piezoelectric materials/properties; Piezoelectricity; Polarization; strain; Thermal stability
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.16603

CuO‐doped (1–x)(Na0.2K0.8)NbO3‐xBaZrO3 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 (PD) developed between Cu2+ ions at Nb5+ 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 PDs. 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 106 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.