Effect of Li content on the microstructure and properties of lead-free piezoelectric(K_0.5Na_0.5)_1-xLi_xNbO₃ ceramics prepared by SPS

Pei Zhao Boping Zhang Ke Wang Limin Zhang Hailong Zhang School of Materials Science and Engineering,University of Science and Technology Beijing,Beijing 100083,China

摘 要：<正>Lead-free piezoelectric(K_0.5Na_0.5)_1-xLi_xNbO₃（x=0at%-20at%）ceramics were synthesized by spark plasma sintering（SPS） at low temperature and the effects of LiNbO₃ addition on its crystal structure and properties were also studied.When the Li content was less than 6at%,a single proveskite phase with the similar structure of(K_0.5Na_0.5)NbO₃ was formed;and a secondary phase with K₃Li₂Nb₅O₁₅ structure was observed in the 6at%≤x≤20at% compositional range.Furthermore,LiNbO₃ existed as the third phase when the Li content was higher than 8at%.The grain sizes increased from 200-500 nm to 5-8μm when the K₃Li₂Nb₅O₁₅ and LiNbO₃ like phases were formed.With increasing Li content,the relative density of the ceramics first decreased from 97% to 93% and then kept constant.The piezoelectric coefficient d₃₃,dielectric constant,and planner electromechanical coupling factor exhibited a de- creasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K₃Li₂Nb₅O₁₅ and LiNbO₃.The formation of dense microstructure with a single phase is necessary in improving the properties of the (K_0.5Na_0.5)_1-xLi_xNbO₃ ceramics.

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