Na/K比对(Na,K,Li)NbO_3压电陶瓷的结构和电学性能的影响

Effect of Na/K ratio on the microstructure and electrical properties of(Na,K,Li)NbO_3 ceramics

采用传统烧结工艺,在1 040℃下烧结2 h制备了(Na_xK_(1-x))_(0.945)Li_(0.055)NbO_3无铅压电陶瓷,研究了Na/K比对陶瓷的相结构、微观形貌和电学性能的影响。x=0.50～0.51时样品呈正交相(O),x=0.51～0.54时样品由正交相(O)转变为正交相-四方相(O-T)共存。介温谱显示O-T相转变温度随Na/K比的增加由75℃降低至室温,所有样品的居里温度T_C保持在460～470℃。随Na含量增加,晶粒尺寸呈减小趋势,剩余极化强度P_r从13.6μC/cm^2减小到6.2μC/cm^2,矫顽场E_c基本保持不变。由于O-T相共存,d_(33)和k_p在x=0.53处分别达到最高值263 pC/N和0.387。Li掺杂明显减低O-T相变温度,Li掺量高于0.05后改变Na/K比可获得具有多形态相变特征的陶瓷样品,且Li含量越高,可出现多形态相变的成分中Na/K比越小。

（NaxK1-x）0.945Li0.055 NbO3 piezoelectric ceramics were prepared by a normal sintering at 1 040 ~C for 2 h. The phase structure, microstructure and electrical properties were investigated with a special emphasis on the effect of the Na/K ratio. The samples at x=0. 50--0. 51 showed an orthorhombic （O） symmetry, while a polymorphic phase transition （PPT） between ortho- rhombic and tetragonal （O-T） phases appeared in samples at x=0. 51--0. 54. The TaT decreased from 75 ℃ to room temperature by increasing the Na/K ratio, while Tc maintained at 460--470 ℃. Increasing Na content led to a decreasing trend in grain size and Pr from 13 to 6μC/cm2 , while the Ec maintained at 2 kV/mm. Sample x=0. 053 showed excellent piezoelectric properties with d33 =263 pC/N, kp =0. 387 owing to the coexisted O-T phases. It was found presently that a PPT was obtainable by modif- ying the Na/K ratio when fixing Li content at a level higher than 0. 05, although the PPT was usually tailored by optimizing Li content. The composition of the ceramics with PPT characteristics showed a decreasing trend in the Na/K ratio when increasing Li content.