Microstructure, phase structure and electrical properties of 0.954K_(1-x)Na_xNbO_3-0.04Bi_(0.5)Na_(0.5)ZrO_3-0.006BiFeO_3 lead-free ceramics

摘要

In this work, 0.954K_(1-x)Na_xNbO_3-0.04Bi_(0.5)Na_(0.5) ZrO_3-0.006BiFeO_3 (KNVN-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 (7"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 ℃, ε_r ~ 2304 and tan 5 ~ 0.029) was obtained at the ceramics with x = 0.56 sintered at 1090 ℃, 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 KNVN-BNZ-BF ceramic is a promising candidate for piezoelectric devices.