Microstructure and electrical properties of Li0.5Bi0.5TiO3-modified (Na0.5K0.5)NbO3 lead-free piezoelectric ceramics
Lead-free piezoelectric ceramics (1− x )(K 0.5 Na 0.5 )NbO 3 – x Li 0.5 Bi 0.5 TiO 3 (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: d 33 =172pC/N, k p =0.37, r =1479, tanδ =0.015 and T c =381°C, while the mechanical quality factor remains reasonably high ( Q m =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- x LBT ( 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.