Preparation and Properties of （Na0.50＋xK0.50-2xLix）Nb0.9Ta0.1O3 Lead-Free Piezoelectric Ceramics by Sol-Gel Method

采用溶胶–凝胶法制备Li＋取代（K0.5Na0.5）＋及Ta5＋取代Nb5＋的（K0.5Na0.5）NbO3陶瓷粉体,采用无压烧结工艺制备（Na0.50＋xK0.50–2xLix）Nb0.9Ta0.1O3（x=0,0.02,0.04）陶瓷样品。研究了前驱体煅烧温度对陶瓷粉体物相组成的影响。分析了不同Li＋掺杂量对样品物相组成、微观结构、体积密度及电学性能的影响。结果表明：前驱体的最佳煅烧温度为600℃,通过透射电子显微镜分析陶瓷粉体的粒径为49nm;不同Li＋掺杂量制备的（Na0.50＋xK0.50–2xLix）Nb0.9Ta0.1O3陶瓷样品均为正交相钙钛矿结构;随着Li＋掺杂量的增加,（Na0.50＋xK0.50–2xLix）Nb0.9Ta0.1O3陶瓷的体积密度先增大后减小,介电常数逐渐升高,压电常数先降低再升高,剩余极化强度逐渐升高。Li＋掺杂量x为0.04时样品的压电常数（d33=94pC/N）、相对介电常数（εr=684.33）及剩余极化强度（Pr=98.27μC/cm2）较好。

Preparation and Properties of (Na0.50+xK0.50-2xLix)Nb0.9Ta0.1O3 Lead-Free Piezoelectric Ceramics by Sol-Gel Method

The ceramic powders, in which Li + substituted （K0.5Na0.5 ） + and Ta5+ substituted Nb 5+ , were prepared by a sol–gel method, and the (Na_0.50+xK_0.50-2xLi_x)Nb_0.9Ta_0.1O₃ （x=0,0.02,0.04） ceramics were prepared via a pressureless sintering method. The effect of calcining temperature on the phase composition of ceramic powders was investigated. The influence of the Li + substitution on the phase composition, microstructure, density and electrical properties of the ceramics was systematically analyzed. The results show that the optimal calcining temperature is 600 ℃. The analysis by transmission electron microscope indicated that the average size of the ceramic powders was 49 nm. The(Na_0.50+xK_0.50-2xLi_x)Nb_0.9Ta_0.1O₃ceramics had a single-phase perovskite structure with the orthorhombic symmetry. The density of the (Na_0.50+xK_0.50-2xLi_x)Nb_0.9Ta_0.1O₃ ceramics firstly increased and then decreased with the increase of Li + content, while piezoelectric constant had the opposite transformation. The dielectric constant and remnant polarization were both improved when Li + content was increased. When Li + content was 0.04, the samples had an excellent piezoelectric constant （d 33 = 94 pC/N）, relative dielectric constant （εr = 684.33） and remnant polarization （Pr = 98.27 μC/cm 2 ）.