Phase evolution and associated high piezoelectric properties of sodium potassium niobate-based piezoelectric ceramics

(1-x)K0.5Na0.5Nb0.965Sb0.035O3-x (Bi0.9Al0.1)(0.5))Na0.5Zr0.42Hf0.58O3 [abbreviated as (1-x)KNNS-xBANZH] ceramics were synthesized by conventional solid reaction method to investigate combined effects of Al and Hf on electrical properties of sodium potassium niobate-based ceramics. The results showed that rhombohedral-tetragonal (R-T) phase boundary was constructed at x = 0.04-0.05 through co-doping, which was demonstrated by refined X-ray diffraction patterns, Raman spectra, transmission electron microscope analysis and temperature-dependent dielectric constants. Consequently, the ceramics with x = 0.045 exhibited significantly improved piezoelectric properties (d(33) -451 pC/N, d(33)* -404 p.m./V and k(p)similar to 0.46). According to calculated intrinsic piezoelectric constants (d(init)) by Rayleigh law, reversible non-180 degrees domain motion and efficient domain wall motion were of essential importance for x = 0.045, which also contributed a lot to d(33)*. Together with scanning electron microscope analysis, R-T phase coexistence and fine grains accounted for the property enhancement. As a result, the addition of (Bi0.9Al0.1)(0.5)Na0.5Zr0.42Hf0.58O3 [abbreviated as BANZH] is an effective method to promote electrical properties of K0.5Na0.5Nb0.965Sb0.035O3 [abbreviated as KNNS] piezoceramics and the ceramics with optimized electrical properties can be treated as promising candidates for Pb-based piezoceramics in some usage fields. (C) 2020 Elsevier B.V. All rights reserved.