Microstructure and electrical properties of (1-x)K0.5Na0.5NbO3–xBi0.5Na0.5Zr0.85Sn0.15O3 lead-free ceramics

Highlights: • Pure and dense KNN-based ceramics were synthesized by solid reaction method. • The correlation between microstructure and electrical properties was established. • The phase coexistence of R-T was obtained in the range of 0.05 ≤ x < 0.07. • The ceramics with x = 0.05 possess a large d₃₃ and a high T_C. • The origin of such enhanced properties was attributed to the R-T phase coexistence. In this work, we simultaneously obtained a large d₃₃ and high T_C in a lead-free piezoelectric system of (1-x)K_0.5Na_0.5NbO₃–xBi_0.5Na_0.5Zr_0.85Sn_0.15O₃ [(1-x)KNN–xBNZS]. This lead-free piezoelectric system was synthesized by conventional solid-state method. We investigated the microstructure and electrical properties of this system. The rhombohedral-tetragonal (R-T) phase coexistence is demonstrated in the ceramics with 0.05 ≤ x ≤ 0.06. Owing to the R–T phase coexistence as well as the enhancement of ferroelectric and dielectric properties, the ceramics with x = 0.05 showed a large d₃₃ of ∼350 pC/N together with a high T_C of ∼315 °C, thereby illustrating that it is an effective way to obtain both large d₃₃ and high T_C in KNN-based ceramics. It is believed that such a ceramic system with large d₃₃ and high T_C is one of the promising candidates for piezoelectric devices.