Structure and Electrical Properties of (1-x)[(K_0.5Na_0.5)_0.95Li_0.05](Nb_0.95Sb_0.05)O₃-xSrTiO₃ Lead-Free Piezoelectric Ceramics with Improved Temperature Stability

Abstract

Lead-free piezoelectric ceramics (1-x)[(K_0.5Na_0.5)_0.95Li_0.05](Nb_0.95Sb_0.05)O₃-xSrTiO₃ (abbreviated as KNLNS-xST) were sintered by the conventional method. The effects of SrTiO₃ content on the structure, the electrical properties and the temperature stability of ceramics were investigated. The X-ray diffraction patterns revealed that all the ceramics have a perovskite structure, and the SEM micrographs revealed that the grain size of the ceramics was decreased with the increase of SrTiO₃ content_. The partial substitution of SrTiO₃ decreased the Curie temperature (T_c) and shifted the orthorhombic–tetragonal phase transition temperature (T_O–T) to below room temperature. It was found that the ceramics with x = 0.008 possess optimum piezoelectric properties (d₃₃ = 250 pC/N, k_p = 51.7%, ϵ_r ∼1143 and tanδ ∼ 4.45%), and the ceramics with x = 0.015 exhibit improved temperature stability, due to the shift of T_O-T to below room temperature. These results indicate that these materials are promising candidates for lead-free piezoelectric ceramics for practical applications.

Acknowledgment

This work was supported by the National Science Foundation of China (11075110).