Preparation and Characterization on Piezo-/Ferro-electric Properties of(1-x)(KNN+LT)+xBI Ceramics

Lead free ferroelectric ceramics,(1-x)(0.97Na0.5K0.5NbO3+0.03LiTaO3)+xBiInO3[(1-x)(KNN+LT)+xBI] ternary solid solution system were prepared by conventional solid state reaction method. The polycrystal structure, dielectric and piezo-/ferro-electric properties were systematically characterized. The results show that the(1-x)(KNN+LT)+ xBI ceramics present pure perovskite structure in which the orthorhombic and tetragonal phases coexist at room temperature. With increasing of BI content, the tetragonal phase and the lattice parameter increase gradually and the Curie temperature Tc decreases, while the phase transition temperature To-t from orthorhombic to tetragonal phase increases. With more BI addition, the electric properties decrease with the appearance of oxygen vacancy due to Bi loss at high temperature. The optimal properties are achieved in the(1-x)(KNN+LT)+xBI ceramics(x=0.0015) with the Curie temperature Tc= 400℃, phase transition temperature To-t =126℃, piezoelectric constant d33 =160 pC/N, remnant polarization Pr=19.26 μC/cm2 and coercive field Ec =7.75 kV/cm.