Nonlinear piezoelectricity in Li-modified (K,Na)NbO₃system ceramics

Abstract

The effects of Li substitution on the nonlinear piezoelectricity in lead-free (K,Na)NbO 3 (KNN) system ceramics were studied. The nonlinear piezoelectricity causes nonlinear phenomena such as the generation of nonlinear voltages, a change in the resonance frequency, and current jumping under high-power vibration. The magnitude of the nonlinear piezoelectricity was estimated by measuring the third-harmonic voltage generated in samples during constant-current driving. With the increase in the amount of substituted Li, the nonlinear piezoelectricity decreased and became a minimum at the phase boundary composition. The nonlinear piezoelectric coefficient at the phase boundary composition was less than one-tenth of the value in the nonsubstituted KNN ceramic.

Improvement effects of sinterability due to B-site excess composition in (K,Na)NbO3system ceramics

“…To reduce the sintering temperature of KNN system ceramics, we improved the sintering process or the preparation procedure of crystal particle templates for the orientation control. 1,17,[27][28][29]31) The A/B stoichiometry of KNN ceramics considerably affects the sinterability. It has been reported that the sintering temperature is lower for the KNN samples with excess amounts of alkali (A-site) relative to niobite (B-site) in the perovskite structure compared with that of the stoichiometric samples.…”

Orientation factor and piezoelectric property in textured (K,Na)NbO3system ceramics with minimal templates

“…[18][19][20][21][22][23][24][25][26][27][28][29][30] On the other hand, even when the templates with smaller sizes are employed, their grain sizes are usually one or two orders of magnitude larger than those of calcined powder. 1,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][27][28][29][30][31][32][33][34][35][36][37][38][39] To reduce the sintering temperature, it is more reasonable to reduce the mixing ratio of the templates to the calcined powder. In addition, even in the single-step molten salt synthesis, many 2SN 23,24,26,35) and relatively costly fabrication processes are needed to produce a large amount of NN templates.…”