Microstructure and electrical properties of (1 -x)(K_(0.5)Na_(0.5))NbO_3-xBiFeO_3 piezoelectric ceramics

摘要

Lead-free ceramics (1-x)(K_(0.5)Na_(0.5))NbO_(3-x)BiFeO_3 doped with 1 mol% Fe_2O_3 (KNNBF/x) have been synthesized by pressureless sintering. With the Fe_2O_3 doping, the KNNBF/x ceramics can be well sintered at 1085-1100 ℃ and exhibit a pure perovskitc structure with x< 0.013. It was found that the crystal structure of the KNNBF/x ceramics changed from orthorhombic to tetragonal and then to pseudocubic phase with the increase of BiFeO_3 content. The compositionrnKNNBF/0.013 near the tetragonal symmetry that separates the orthorhombic and pseudocubic phases exhibits improved electrical properties: d_(33)= 173 pC/N, k_p = 0.40, ε_r = 905, tan δ = 4%, P_r = 26 μC/cm~2, and E_c = 11.2 kV/cm, with a high Curie temperature (T_c) of about 388 ℃. Our results suggest that KNNBF/x are promising lead-free high temperature piezoelectric ceramics.