Electrical Performance and Conduction Mechanism of Potassium Sodium Niobate-Based Lead-Free Piezoceramics via Two-Step Sintering Route

(1-x)(Li0.02Na0.48K0.48Ag0.02)(Nb0.95Sb0.05)O-3-x(Ba0.4Bi0.3Na0.3)ZrO3 (LNKANbS-xBBiNZ, x = 0.04, 0.045, 0.05, 0.055 and 0.06) lead-free piezoelectric ceramics were prepared by the conventional solid-state reaction method via the two-step sintering route. The effects of the content of BBiNZ on electrical properties and microstructural morphology of the LNKANbS-xBBiNZ ceramics were studied systematically. The designing of forming rhombohedral-tetragonal phase boundary in the LNKANbS-xBBiNZ system is confirmed by XRD Rietveld refinement and Raman spectroscopy, whose phase proportion is affected greatly by the BBiNZ amount. The LNKANbS-xBBiNZ ceramics exhibit complicated dielectric behavior, whose dielectric response characteristic can be fitted by the quadratic law and the Curie-Weiss law, and both having some deviation. The high-temperature conductivity of the LNKANbS-0.045BBiNZ ceramics is controlled by oxygen vacancies detected by both conductive activation energy and relaxation activation energy fitting. The LNKANbS-0.045BBiNZ ceramics exhibit excellent electrical properties, correlating with appropriate R-T phase composition proportion and improved densification and microstructural homogeneity obtained by adjusting the BBiNZ content and using the two-step sintering method.