Lead-free ceramics Bi0.5(Na0.925-x-yLi0.075KxAgy)0.5TiO3have been prepared by an ordinary sintering technique, and their ferroelectric and piezoelectric properties have been studied. From the results of x-ray diffraction, Li+, K+and Ag+diffuse into the Bi0.5Na0.5TiO3lattices to form a solid solution with a pure perovskite structure, and a morphotropic phase boundary (MPB) exists at 0.15 < x < 0.25. Compared with pure Bi0.5Na0.5TiO3, the substitutions of K+and Ag+lower the coercive field Ecgreatly and increase the remanent polarization Prof the ceramics. Because of the MPB and low Ec, the piezoelectricity is significantly enhanced. For the ceramics with compositions near the MPB, the piezoelectric coefficient d33= 178-219 pC N-1, the planar electromechanical coupling factors kP= 35-39% and kt= 44-51%. Also, the depolarization temperature Tdreaches a minimum value near the MPB. The results of the ferroelectric and dielectric properties at high temperatures suggest that the ceramics may contain both the polar and non-polar regions at temperatures above Td.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Acoustics and Ultrasonics
- Surfaces, Coatings and Films