Enhanced temperature stability in the R–T phase boundary with dominating intrinsic contribution

Abstract

In this study, 0.96KNNS_x–0.01SZ–0.03BNZ ceramics (x = 0–0.08) were used as examples to illustrate the effects of phase boundaries on strain property and temperature stability. The addition of Sb⁵⁺ resulted in a rhombohedral–tetragonal (R–T) phase boundary at x = 0.05–0.07, as confirmed by temperature-dependent Raman spectra. In the R–T region, an improved piezoelectric constant (d₃₃ = 390–440 pC N⁻¹) and high unipolar strain (S_uni = 0.14–0.15%) were observed due to the dominating intrinsic contribution. More importantly, a favorable temperature stability of S_uni was observed in the ceramics with x = 0.05; for example, there was a slight variation of +5% to −13% when the temperature was increased from 20 °C to 180 °C. Through systematic investigations of composition and temperature-dependent strain, methods to improve S_uni and consolidate its temperature stability in KNN-based ceramics were subsequently suggested. We believe that this study can promote the understanding and design of KNN-based ceramics with high strain and favorable temperature stability.