Lead-free K0.5Na0.5NbO3-Bi0.5Li0.5ZrO3-BiAlO3 ternary ceramics: Structure and piezoelectric properties

Lead-free perovskite (0.995-x)(K0.5Na0.5)NbO3-x(Bi0.5Li0.5)ZrO3-0.005BiAlO(3) ternary piezoelectric ceramics were projected and prepared by a conventional solid-state method. A research was conducted on the effects of (Bi0.5Li0.5)ZrO3 content on the structure and piezoelectric properties of the ceramics. By combining the X-ray diffraction patterns with the temperature dependence of dielectric properties, a rhombohedral-orthorhombic-tetragonal phase coexistence was identified for the ceramics with 0.02 ae x ae 0.025, and a rhombohedral-tetragonal phase boundary was determined in the composition x = 0.03. Upon further increasing the (Bi0.5Li0.5)ZrO3 content, the rhombohedral-tetragonal phase boundary transformed to a single rhombohedral structure with x ae0.035. An obviously improved piezoelectric activity was obtained for the ceramics with compositions in and around the rhombohedral-tetragonal phase boundary, among which the composition x = 0.025 exhibited the maximum values of piezoelectric constant d (33), and planar and thickness electromechanical coupling coefficients (k (p) and k (t)), of 252 pC/N, 0.366, and 0.466, respectively. In addition, the ceramic with x = 0.025 was found to possess a relatively high Curie temperature of 368 A degrees C, suggesting it may have a prospect for applications at elevated ambient temperatures.