Piezoelectric and dielectric properties of 0.995K 0.48 Na 0.48 Li 0.04 Nb (1−x) Sb x O 3 –0.005BiAlO 3 lead-free piezoelectric ceramics

Abstract Lead-free 0.995 K 0.48 Na 0.48 Li 0.04 Nb (1 −x ) Sb x O 3 –0.005BiAlO 3 piezoelectric ceramics with perovskite structure were designed and prepared with conventional ceramic fabrication techniques. The phase transitions of the ceramics were determined by X-ray diffraction patterns and the temperature dependence of dielectric properties. The ceramics possessed an orthorhombic–tetragonal phase boundary with x = 0 and exhibited the coexistence of rhombohedral–orthorhombic and orthorhombic–tetragonal phase boundaries at around room temperature, with 0.02 ≤ x ≤ 0.03. Upon further increasing the Sb content, the crystal structure transformed to the rhombohedral-tetragonal phase coexistence in the composition range of 0.04 ≤ x ≤ 0.05. Next, the phase structure turned to a sole rhombohedral symmetry with x ≥ 0.06. A clearly enhanced piezoelectric activity was demonstrated for the ceramic with the rhombohedral-tetragonal phase boundary composition x = 0.05, where the values of piezoelectric constant d 33 , planar and thickness electromechanical coupling coefficients reached 205 pC/N, 0.360 and 0.437, respectively.