Phase transitional behavior and electrical properties of lead-free (K0.44Na0.52Li0.04)(Nb0.96−xTaxSb0.04)O3 piezoelectric ceramics

Lead-free (K0.44Na0.52Li0.04)(Nb0.96−xTaxSb0.04)O3 piezoelectric ceramics have been synthesized by conventional solid state sintering process. Two morphotropic phase boundaries (MPBs) respectively corresponding to the orthorhombic to tetragonal and tetragonal to pseudocubic phases are observed with increasing x. The ceramics with x=0.20 between the two MPBs show significantly enhanced electrical properties, which are as follows: piezoelectric constant d33=252pC∕N, planar coupling coefficient kp=0.42, dielectric constant εr=1503, and dielectric loss tanδ=0.025, and they show good stability. Lead-free superthin buzzer disks have been prepared by using piezoceramic membrane with x=0.20. (K0.44Na0.52Li0.04)(Nb0.96−xTaxSb0.04)O3 ceramics are very promising as lead-free replacements for lead zirconate titanate.