采用传统固相反应法制备了K0.5Na0.5NbO3-xmol%La2O3(简称KNN-xLa)系列无铅压电陶瓷,研究了不同La2O3含量(x=0.0,0.05,0.15,0.25,0.35,0.5,1.0)样品的物相组成、显微结构、压电及介电性能。实验结果表明:La2O3的加入并没有改变陶瓷的相结构,体系仍为单一正交相钙钛矿结构。随着掺杂量x的增大样品的压电系数(d33)、机械品质因子(Qm)、平面机电耦合系数(kp)和样品密度(ρ)都呈现先增大后减少的变化趋势,而介质损耗(tanδ)呈现先变小后增大的变化趋势,烧成温度则随着x的增大而升高。当x=0.15时,材料的综合性能达到最佳,其中ρ=4.52g/cm3,d33=120pC/N,Qm=130,kp=0.41,tanδ=0.021。此外,随着x的增大,居里温度Tc则呈现出先升高后降低的趋势,而正交相向四方相的转变温度To-t与Tc变化相反,且当x=0.15时,To-t=189℃,Tc=404℃。
In this paper, Lead-free piezoelectric ceramics K0.5Na0.5NbO3-xmol%La2O3 (abbreviated as KNN-xLa) were prepared by traditional solid state reaction. The phase structure, microstructure, piezoelectric properties and dielectric properties were studied for KNN-xLa samples with different La2O3 content (x=0.0, 0.05, 0.15, 0.25, 0.35, 0.5, 1.0). It was found that the A-site substitution of La3+ does not change the crystal structure within the studied doping level and all the ceramics possess a single-phase perovs...