Crystal structure and piezoelectric properties of 0.79(NaBi)TiO-0.05BaTiO-0.16(KBi)TiO ceramics prepared by solid-state method.

The solid-state reaction technique was employed to synthesize lead-free ceramics, specifically (1-x-y)(NaBi)TiO-xBaTiO-y(KBi)TiO. For attaining a pure perovskite phase, it was found that the optimal calcination temperature is 1000 °C, maintained for a duration of 4 h. Through X-ray diffraction (XRD) analysis, the morphotropic phase boundary (MPB) was detected in (1-x-y)NBT-xBT-yKBT ceramics for certain molar compositions, specifically in 0.95NBT-0.05BT, 0.84NBT-0.16KBT, and 0.79NBT-0.05BT-0.16KBT. For 4 h, the sintering temperature was fixed at 1100 °C in order to improve densification. Scanning electron microscopy (SEM) images exhibited homogeneous distribution and dense packing of the grains in the ceramics, indicating a uniform microstructure. These materials exhibited favorable characteristics, including high dielectric permittivity, low dielectric loss, and diffused phase transition behavior. The ceramics composed of 0.79NBT-0.05BT-0.16KBT exhibited the highest piezoelectric constant (d33 = 148 pC/N) and electromechanical coupling factor (kp = 0.292) among all compositions studied. This enhancement in piezoelectric properties can be attributed to the presence of the morphotropic phase boundary (MPB) in the material. This study introduces an interesting approach to enhance the performance of lead-free ferroelectric systems with formula 0.79(NaBi)TiO-0.05 BaTiO-0.16 (KBi) TiO.