High piezoelectric performance in KNN-based ceramics with multiphase coexistence for plateau climate applications

Abstract

As monitoring techniques are increasingly used in extreme environments, performance in extremely cold regions becomes a critical issue for sensing materials and devices. Due to reduced polarity and poor polarization rotation under external fields, optimizing the piezoelectric response remains challenging. Herein, rhombohedral–orthorhombic–tetragonal (R–O–T) phase boundary was successfully formed at −50 to 50 °C, with decreased phase transition temperatures in potassium sodium niobate ceramics. High polarity and enhanced polarization rotation were revealed with the R–O–T phase boundary, which was attributed to the refined domain structure and lowered polarization anisotropy, both of which could flatten the polarization energy barrier. Consequently, large piezoelectric properties (d₃₃ = 300–420 pC N⁻¹, k_p = 0.36–0.38), along with improved ferroelectricity, were achieved at −40 to 50 °C for the samples, which were superior to those of pure phase or rhombohedral–orthorhombic (R–O) phase boundary compositions. This study demonstrates a strategy for developing high-performance piezoelectric materials suitable for extremely cold regions, facilitating the application of monitoring techniques in plateau environments.