Microstructure and electrical properties of Li0.5Bi0.5TiO3-modified (Na0.5K0.5)NbO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (1 − x)(K0.5Na0.5)NbO3–xLi0.5Bi0.5TiO3(KNN–LBT) were synthesized by conventional sintering process. Characterized effects of LBT on the microstructure and electrical properties of ceramics were studied. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases lies close to 0.01–0.02. The ceramic with x = 0.02 near the MPB achieves remarkable electrical properties: d33 = 172 pC/N, kp = 0.37, ɛr = 1479, tan δ = 0.015 and Tc = 381 °C, while the mechanical quality factor remains reasonably high (Qm = 102), revealing that the LBT-doping changes the KNN to “hard” piezoelectric ceramics. The addition of a small amount of LBT increases the relative density, which reaches an optimum value of 96.4% with x = 0.02. Moreover, impedance for high piezoelectric properties in (1 − x)KNN–xLBT (x = 0.0, 0.01, 0.02 and 0.05) ceramics were also discussed. It is found that the addition of LBT (x = 0.02) can improve poling procedures of the ceramics. These results demonstrate that the ceramic (x = 0.02) is an attractive candidate for lead-free piezoelectric materials.