Dielectric property and relaxor phase transition of NBT-KBT-LBT ceramics

(1-x)(0.8Na0.5Bi0.5TiO3- 0.2K0.5Bi0.5TiO3)- xLi0.5Bi0.5TiO3(NBT-KBT-xLBT) lead-free piezo-electric ceramics were prepared by the conventional ceramic preparation method. Crystal structure, dielectric, ferroelectric and piezoelectric properties of the ceramics were investigated. According to XRD patterns, the morphotropic boundary lies in the composition range of 0.08≤x≤0.10. The temperature dielectric anomalous peak Tf which was corresponding to the depolarization temperature towards to higher temperature while the ferroelectric-paraelectric phase transition peak Tm shift towards to lower temperature. Relaxor phase transition characteristics become stronger. The relationship between relaxation phase transition characteristics and A-site local structure are further discussed based on inhomogeneous distribution and disorder range in atomic scale. The ferroelectric properties of the NBT-KBT ceramics are further improved with the introduction of the LBT content. And the coercive field Ec decreases from 14.5 kV/cm (x=0.06) to 12.3 kV/cm (x=0.12). The piezoelectric activity was enhanced with an increase in LBT content and piezoelectric constant d33 reaches 145 pC/N at the morphotropic phase boundary(x=0.10). The lower sintering temperature, higher d33 and lower Ec value for NBT-KBT system could be obtained by the LBT incorporation.