Giant piezoelectric effect and high strain response in (1−x)(K0.45Na0.55)(Nb1−ySby)O3 -xBi0.5Na0.5Zr1−zHfzO3 lead-free ceramics

Abstract Here, we reported a high electric field-induced strain value of 0.34% ( S max / E max  = 901 pmV −1 ) under a low electric field of 3.7 kV/mm as well as a large d 33 (∼418 pC/N) in the (1− x )(K 0.45 Na 0.55 )(Nb 1− y Sb y )O 3 - x Bi 0.5 Na 0.5 Zr 1− z Hf z O 3 ceramics with x  = 0.035, y  = 0.04, and z  = 0.75, which is mainly ascribed to the involvement of R-T phase boundary as well as optimized compositions (Hf/Zr). We investigated the relationships among composition, phase boundary, and electrical properties through (1− x )(K 0.45 Na 0.55 )(Nb 1 −y Sb y )O 3 - x Bi 0.5 Na 0.5 Zr 1 −z Hf z O 3 ceramics. The R-T phase boundary is constructed in the ceramics with 0.035 ≤  x  ≤ 0.05, 0.04 ≤  y  ≤ 0.08, and 0 ≤  z  ≤ 1.0. Meanwhile, the highest piezoelectric coefficient of d 33  ∼ 442 pC/N were obtained for x  = 0.0375, y  = 0.04, and z  = 0.15 due to the coexistence of R and T phases. Both dielectric constant and remanent polarization can gain the most excellent values for R-T, which is responsible for the enhanced piezoelectricity. We believe that such an investigation can promote the electrical properties of (K, Na)NbO 3 -based ceramics and then provide practical applications.