Effects of CuO doping on the structure and properties lead-free KNN-LS piezoelectric ceramics

(0.95Na_0.5K_0.5NbO₃-0.05LiSbO₃)-x mol% CuO (KNN-LS-xCuO) lead-free piezoelectric ceramics have been fabricated by a conventional solid-state reaction route at a lower sintering temperature and the effects of CuO-dopant on structure and properties of KNN-LS ceramics have been studied. It is found that the addition of CuO significantly improves the sinterability and properties of KNN-LS ceramics. X-ray diffraction data shows that a small amount of CuO does not change the phase structure of KNN-LS and a dense microstructure with smaller and more uniform grains is developed, probably due to liquid-phase sintering. With the increase of CuO content x, the relative density, d ₃₃ , k _p , tanδ and Q _m have been improved obviously when x < 0.45 due to the presence of the liquid phase and the refined grains, but excessive CuO would degrade the comprehensive properties of KNN-LS-xCuO ceramics. The best specimen with a high relative density of 98.53 % was fabricated when x = 0.45 at 1,060 °C, relating constants respectively are: d ₃₃  = 175pC/N, k _p  = 0.46, ε _r  = 551.23, tanδ = 1.41 %, Q _m  = 41.5.