Morphotropic phase boundary study of the BNT-BKT lead-free piezoelectric ceramics

A lead-free piezoelectric ceramic binary system based on bismuth sodium titanate (Bi_0.5Na_0.5)TiO₃ (BNT)-bismuth potassium titanate (Bi_0.5K_0.5)TiO₃ (BKT) was synthesized by conventional mixed-oxide technique. The XRD analysis showed that the rhombohedral-tetragonal morphotropic phase boundary (MPB) of the Bi _0.5 (Na_1-xK_x)_0.5 TiO₃ system was in the composition range of x = 0.16 - 0.20. In addition, the piezoelectric properties of this system were also investigated. It was indicated that the piezoelectric properties are better with the compositions near the rhombohedral phase within the MPB than the compositions near the tetragonal phase.