Bright reddish-orange emission and good piezoelectric properties of Sm2O3-modified (K0.5Na0.5)NbO3-based lead-free piezoelectric ceramics

Abstract

Reddish orange-emitting 0.948(K0.5Na0.5)NbO3-0.052LiSbO3-xmol%Sm2O3 (KNN-5.2LS-xSm2O3) lead-free piezoelectric ceramics with good piezoelectric properties were fabricated in this study, and the photoluminescence and electrical properties of the ceramics were systematically studied. Results showed that Sm2O3 substitution into KNN-5.2LS induces a phase transition from the coexistence of orthorhombic and tetragonal phases to a pseudocubic phase and shifts the polymorphic phase transition (PPT) to below room temperature. The temperature stability and fatigue resistance of the modified ceramics were significantly improved by Sm2O3 substitution. The KNN-5.2LS ceramic with 0.4 mol. % Sm2O3 exhibited temperature-independent properties (25–150 °C), fatigue-free behavior (up to 106 cycles), and good piezoelectric properties (d33* = 230 pm/V, d33 = 176 pC/N, kp = 35%). Studies on the photoluminescence properties of the samples showed strong reddish-orange emission upon blue light excitation; these emission intensities were strongly dependent on the doping concentration and sintering temperature. The 0.4 mol. % Sm2O3-modified sample exhibited temperature responses over a wide temperature range of 10–443 K. The maximum sensing sensitivity of the sample was 7.5 × 10−4 K at 293 K, at which point PPT occurred. A relatively long decay lifetime τ of 1.27–1.40 ms and a large quantum yield η of 0.17–0.19 were obtained from the Sm-modified samples. These results suggest that the KNN-5.2LS-xSm2O3 system presents multifunctional properties and significant technological potential in novel multifunctional devices.