中文摘要：

采用传统陶瓷工艺和电子陶瓷公司在工业生产中使用的原料，制备了LiNbO3改性的K0.5Na0.5NbO3基无铅压电陶瓷（KNN＋xLN，x=0～10％（摩尔分数）），并研究了陶瓷的晶相、显微结构和电性能。当x≤4％时，陶瓷为单一的正交钙钛矿结构；当x≥6％时，出现了四方钨青铜结构的K3Li2Nb5O15第二相。介电常数-温度曲线表明，随着LiNbO3含量的增加，陶瓷的正交→四方结构的相变温度TO-T向低温方向移动，而四方→立方结构的居里温度Tc向高温方向移动。当x=4％时，陶瓷具有较好的性能：相对密度达98％，压电常数d33=116pC／N，机电耦合系数kp=40．6％，剩余极化强度Pτ=21．0μC／cm^2，矫顽场Ec=0．96kV／mm，Tc=452℃。该体系陶瓷具有较高的Tc（420-495℃）和较大的kp，是一种应用前景良好的高温压电铁电材料。

英文摘要：

LiNbO3 modified K0.5 Na0. 5 NbO3 （abbreviated as KNN ＋ xLN, x = 0 - 10 %） lead-free piezoelectric ceramics have been synthesized by using the conventional mixed oxide process and electronic grade raw materials. The crystalline phase, microstructure and electric properties of the ceramics were studied. When x≤4%, the ceramics with perovskite structure possesses the orthorhombic phase, and when x ≥ 6%, a second phase of K3 Li2 Nb5 O15 with tetragonal tungsten bronze structure appears. With LiNbO3 amount increasing, the phase transition temperature （TO-T） of orthorhombic to tetragonal is shifted to the lower temperatures while the Curie temperature Tc is shifted to the higher temperatures in the dielectric constant-temperature curves. At x=4%, the optimal electric properties were obtained., piezoelectric constant d33 = 116 pC/N, planar electromechanical coupling factor kp =40.6%, remanent polarization Pr=21.0 μC/cm^2, coercive filed Ec=0.96 kV/mm, and the Curie temperature Tc = 452 ℃ respectively. The results show that KNN＋xLN is a good candidate for lead-free piezo-and ferroelectric ceramics for a wide range of temperature application because of their larger planer electromechanical coupling coefficient and higher Curie temperature.