Low-Temperature Sintering of Li-Modified (K, Na)NbO_3 Lead-Free Ceramics: Sintering Behavior, Microstructure, and Electrical Properties

摘要

With the assistance of excess Na_2O additives, LiNbO_3-doped (K, Na)NbO_3 lead-free piezoceramics were successfully prepared by conventional sintering at a temperature as low as 950℃. Shrinkage curve measurement and micrograph observation elucidate that the nature of the densiflcation behavior at 950 ℃ is liquid phase sintering, during which the liquid phase penetrated between initial small particles and large quadrate grains of 20-40 urn formed in the solution-precipitation process. Although the density and grain size show inappreciable changes during the final stage of the coalescence process, the piezoelectric properties of the sintered samples are greatly influenced by the soaking time, depending on the optimization of which the piezoelectric constant d_(33) and the planar mode of the electromechanical coupling factor k_p reached 280 pC/N and 48.3%, respectively. The present study revealed that good piezoelectric properties can be obtained in the Li-doped KNN ceramics even by normal sintering at a reduced temperature (950℃).