Effects of LiF on the Structure and Electrical Properties of (Na_0.52K_0.435Li_0.045)Nb_0.87Sb_0.08Ta_0.05O₃ Lead-Free Piezoelectric Ceramics Sintered at Low Temperatures

Abstract

The (Na 0.52 K 0.435 Li 0.045 )Nb 0.87 Sb 0.08 Ta 0.05 O 3 (KNNLST) + x wt% LiF piezoelectric ceramics, where x = 0, 2, 4, and 6, have been fabricated successfully by the conventional solid-state reaction method. The effect of LiF on the sintering temperature, the structure and electrical properties of KNNLST ceramics was systematically studied. The LiF addition significantly reduced the sintering temperature of the ceramics from 1100℃ to 930℃. Experimental results showed that with the doping of LiF, all the ceramic samples could be well sintered and exhibit a dense, pure perovskite structure. With increasing LiF content, the tetragonal-orthorhombic transition point (T O-T ) and the Curie temperature (T c ) of the ceramics shifted to the lower and higher temperatures, respectively. The specimens containing 4 wt% LiF sintered at 930℃ showed the good electrical properties: the density of 4.26 g/cm 3 ; the electromechanical coupling factor, k p = 0.27 and k t = 0.40; the dielectric constant, ε = 744; the piezoelectric constant (d 31 ) of 41 pC/N.