采用传统固相烧结工艺, 在1000℃成功制备了致密度较高、微观形貌较好的Li0.05+x(Na0.535K0.48)0.95NbO3 (LxNKN)压电陶瓷. 考察了Li补偿量对LxNKN陶瓷致密度、微观结构、相结构、居里温度及电学性能的影响. 结果发现: 添加过量Li不仅促进陶瓷的烧结, 而且降低陶瓷的烧结温度. XRD图谱分析和相应的晶格常数计算表明, 在x=0.010~0.015范围内出现了四方?正交两相共存的多形态相界(PPT). 由于PPT的出现, 在最佳补偿量x=0.015处, 陶瓷的压电常数d33、机电耦合系数kp、介电常数εr和剩余极化强度Pr分别达到各自的最大值282 pC/N、44%、942和27 μC/cm2. 与化学计量比的LNKN陶瓷相比, LxNKN陶瓷的居里温度随Li补偿量的增加变化很小, 这可能是由于Li主要是起助烧作用而进入主相晶格很少的缘故. 研究工作为低温制备高性能铌酸盐系压电陶瓷提供了一种新的思路.
High dense Li0.05+x(Na0.535K0.48)0.95NbO3 (LxNKN) lead-free piezoelectric ceramics with fine morphology were synthesised by conventional mixed-oxide method at 1000℃, and its microstructure, phase structure and electrical properties were investigated as a function of excessive Li addition. The results revealed that the excess Li content facilitated the sinterability and improved the piezoelectric properties for LxNKN ceramics. A PPT bridging tetragonal and orthorhombic symmetry was found at x= 0.01-0.015 by using the X-ray diffraction patterns and the corresponding calculation of lattice parameters. Owing to such transitional behavior, the piezoelectric coefficient (d33), electromechanical coupling coefficient (kp), dielectric constant (εr) and remanent polarization (Pr) were enhanced to peak values, 282 pC/N, 44%, 942 and 27 μC/cm2, respectively. Compared with LNKN ceramics, the variation in Curie temperature (Tc) by the compensation amount of Li was much smaller for LxNKN ceramics. The reason is that the amount of Li that entered into crystal lattice is relatively rare for LxNKN ceramics. The results provide a way to low-temperature sintering of LNKN-based lead-free piezoceramics with high performance.
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