Microstructure, phase structure and electrical properties of 0.954K1−x Na x NbO3–0.04Bi0.5Na0.5ZrO3–0.006BiFeO3 lead-free ceramics

Abstract

In this work, 0.954K1−x Na x NbO3–0.04Bi0.5Na0.5ZrO3–0.006BiFeO3 (KN x N–BNZ–BF) lead-free ceramics were fabricated by conventional ceramic technique. The effect of K/Na ratio on microstructure, phase structure and electrical properties was systematically investigated. The orthorhombic-tetragonal phase transition temperature (T O–T) increases and rhombohedral–orthorhombic phase transition temperature (T R–O) drops simultaneously with increasing the Na content, leading to an R–O–T phase boundaries in the ceramics with 0.44 ≤ x ≤ 0.60. By tailoring their K/Na ratio and optimizing the sintering temperature, an enhanced electrical properties (e.g. d 33 ~ 438 pC/N, k p ~ 0.51, T c ~ 320 °C, e r ~ 2304 and tan δ ~ 0.029) was obtained at the ceramics with x = 0.56 sintered at 1090 °C, which could be attributed to the preferably density as well as the R–O–T phase boundary nearer the room temperature. Therefore, we think that the KN x N–BNZ–BF ceramic is a promising candidate for piezoelectric devices.