Comprehensive investigation of structural and electrical properties of (Bi, Na) CoZrO3-doped KNN ceramics

Highlights: • KNNS-BNC_xZ possess excellent piezoelectric property: d₃₃ (∼418 pC/N), k_p = 0.48. • The correlations between d₃₃ and grain sizes growth are given and explained. • The visualized crystal structure of ceramics is given to explain its properties. • Excellent performance of thermal stability is obtained. This study utilized the traditional solid state reaction method to fabricate 0.965(K_0.48Na_0.52)Nb_0.96Sb_0.04O₃-0.035[(Bi_0.5Na_0.5)_1-xCo_xZrO₃](KNNS-BNC_xZ) lead-free ceramics for the sake of investigating the influences of BiCoZrO₃-doped on the crystalline structure, microstructure, and dielectric/piezoelectric properties of the ceramics. The KNNS-BNC_xZ ceramics exhibited a perovskite structure, which changed from a three-phase coexistence of rhombohedral-orthorhombic-tetragonal (R-O-T) to orthorhombic (O) with increasing x. The surface morphologies further indicated that different amounts of (BiNa)CoZrO₃ played a large effect on the grain growth. In addition, the optimal combined properties (d₃₃ = 418 pC/N, k_p = 0.48, T_c = 263 °C) were simultaneously obtained at x = 0.1. Particularly, good thermal stability was observed in a broad temperature range (T_a = 265 °C d₃₃ ≥ 351 pC/N). These results induced that KNNS-BNC_xZ ceramics were appropriate candidates for lead-free electronical applications.