Excellent piezoelectric properties of (K, Na)(Nb, Sb)O-3-CaZrO3-(Bi, Ag)ZrO3 lead-free piezoceramics

Abstract

Fe2O3-containing 0.96(K0.5Na0.5)(Nb0.93Sb0.07)-(0.04-x)CaZrO3-x(Bi, Ag)ZrO3 piezoceramics with 0.0 <= x <= 0.04 fabricated at 1090 degrees C show a dense microstructure without any secondary phases. The piezoceramic with x = 0.03 has an ideal rhombohedral-orthorhombic-tetragonal (R-O-T) multi-structure because its constituent structure proportions are similar. Its R-O-T phase transition temperature (TR-O-T) increases with increasing measuring frequency, indicating that this piezoceramic exhibits relaxor properties which develop near its ferroelectric-to-ferroelectric phase transition temperature, that is, its TR-O-T. This piezoceramic has nanodomains that are approximately 3 nm x 20 nm in size. The associated low boundary energies of these domains are expected to facilitate domain rotation. Furthermore, the piezoceramic has an extremely high piezoelectric constant (d(33)) of 680 +/- 10 pC/N, which exceeds the maximum d(33) reported in the literature for similar materials. This high d(33) is attributed to the existence of an ideal R-O-T multi-structure and nanodomains. (C) 2021 Published by Elsevier B.V.