Evolution of phase structure, microstructure and piezoelectric properties in (1-x)(K0.4Na0.6)Nb0.96Sb0.04O3-xCa0.1(Bi0.5K0.5)0.9ZrO3 lead-free ceramics

New lead-free piezoelectric (1 - x)(K0.4Na0.6)Nb0.96Sb0.04O3-xCa(0.1)(Bi0.5K0.5)(0.9)ZrO3 ceramics were projected and prepared by using traditional ceramic preparation techniques, and we investigated the effects of Ca-0.1(Bi0.5K0.5)(0.9)ZrO3 content on their surface microstructure, phase structure and electrical properties. A phase pure perovskite structure was obtained for the ceramics within the studied composition range of 0 <= x <= 0.06, according to X-ray diffraction analysis. Additionally, it was found that adding Ca-0.1(Bi0.5K0.5)(0.9)ZrO3 into the ceramics caused a gradual evolution in the phase structure, and a rhombohedral-tetragonal phase boundary was identified at the composition x = 0.04. The ceramics showed an enhanced piezoelectric activity with compositions near the phase boundary. Furthermore, the phase diagram of the (1 - x)(K0.4Na0.6)Nb0.96Sb0.04O3-xCa(0.1)(Bi0.5K0.5)(0.9)ZrO3 solid solution was built up by combining the X-ray diffraction analysis with the measurement results of the temperature-dependent dielectric behavior. These results indicate that the structural state of (K,Na)NbO3-based ceramics can be easily altered by using a suitable amount of Ca-0.1(Bi0.5K0.5)(0.9)ZrO3 as additive, which will benefit the improvement of piezoelectric properties for such lead-free materials.