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

Here, we reported a high electric field-induced strain value of 0.34% (Smax/Emax = 901 pmV−1) under a low electric field of 3.7 kV/mm as well as a large d33 (∼418 pC/N) in the (1−x)(K0.45Na0.55)(Nb1−ySby)O3 -xBi0.5Na0.5Zr1−zHfzO3 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)(K0.45Na0.55)(Nb1−ySby)O3 -xBi0.5Na0.5Zr1−zHfzO3 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 d33 ∼ 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)NbO3-based ceramics and then provide practical applications.