Large electrostrictive effect and strong photoluminescence properties in Sm2O3-modified lead-free potassium sodium niobate-based piezoelectric ceramics

In this work, the phase transition behavior and electrostrictive and photoluminescence properties of Sm2O3-modified 0.965(K0.48Na0.52)(Nb0.95Sb0.05)–0.035Bi0.5(Na0.82K0.18)0.5HfO3 (KNNS–0.035BNKH) ceramics were investigated. Results showed that the phase structure of the Sm2O3-modified ceramics evolved from coexisting orthogonal and tetragonal ferroelectric phases to a relaxor pseudocubic phase along with the strong destruction of the long-range ferroelectric order. Domain switching in Sm-modified ceramics with a relaxor pseudocubic phase became difficult, evident from the PFM images. Consequently, large electrostrictive effect with an electrostrictive coefficient of 0.022 m4/C2 was obtained in 1.0 mol% Sm-modified samples. With regard to long-term stability, the materials exhibited temperature-independent (20–100 °C) and fatigue−free (up to 105 cycles) behavior, which guarantees their application in various devices. The KNNS–0.035BNKH–xSm ceramics have the advantages of photoluminescence performance with bright orange emission under 407 nm visible light excitation. Overall, KNNS−0.035BNKH−xSm ceramics have broad application prospects in multifunction devices due to their large electrostrictive effect, excellent photoluminescence performance, and long-term stability.