Phase transitional behavior and electrical properties of lead-free (K _0.44Na_0.52Li_0.04) (Nb_0.96-xTa _xSb_0.04)O₃ piezoelectric ceramics

Lead-free (K0.44 Na0.52 Li0.04) (Nb0.96-x Tax Sb0.04) 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 =252 pCN, planar coupling coefficient kp =0.42, dielectric constant εr =1503, and dielectric loss tan δ=0.025, and they show good stability. Lead-free superthin buzzer disks have been prepared by using piezoceramic membrane with x=0.20. (K0.44 Na0.52 Li0.04) (Nb0.96-x Tax Sb0.04) O3 ceramics are very promising as lead-free replacements for lead zirconate titanate.