Effect of Li2O addition on the phase formation, microstructure and electrical properties of 0.79Bi0.5Na0.5TiO3-0.18Bi0.5K0.5TiO3-0.03BiFeO3 ceramics

Abstract Lead-free 0.79(Bi0.5Na0.5TiO3)-0.18(Bi0.5K0.5TiO3)-0.03(BiFeO3)-x(Li2O) (BNT-BKT-BF-xLi) piezoelectric ceramics, with x between 0 and 0.4 wt.%, were prepared by the conventional solid-state reaction method. In all compositions, the samples were calcined at 800 °C for 2 h and sintered at 1100 °C for 2 h. The added Li2O affected the phase formation, microstructure, dielectric and ferroelectric properties of the BNT-BKT-BF-Li ceramics were investigated. All ceramics exhibited coexisting rhombohedral and tetragonal phases. The rhombohedral phase and the average grain size increased with increase in x. All ceramics presented polygon grain shapes with anisotropic grain growth. The depolarization temperature and the maximum temperature (T d and T m) continuously increased with increase in Li2O content. The maximum dielectric constant (ε m) decreased from 6250 to 4868 when x increased from 0 to 0.4 wt.%. The P-E hysteresis loops had their squareness factor increase with rising x, indicating a harder ferroelectric was obtained with higher Li2O doping.