Enhanced temperature stability of piezoelectric properties and electrostrain via a diffused phase transition in LaMnO3-doped (K, Na)NbO3-based ceramics

Modern-generation electronic devices face a significant challenge in enhancing the temperature stability of their electrical properties, which are crucial for their practical applications. This study introduces an effective approach to diffused phase engineering, involving doping LaMnO ₃ to induce diffused phase transition. Consequently, the material achieves temperature-insensitive piezoelectric properties and electrostrain. We combine temperature-dependent X-ray diffraction, first-principle calculations, and other dielectric/piezoelectric properties to elucidate the relationship between dopants, structures, and properties in the (0.96-x)K _0.48Na _0.52NbO ₃-0.04Bi _0.5Na _0.5ZrO ₃-xLaMnO ₃ systems. Additionally, LaMnO ₃ doping in KNN-based ceramics maintains long-range ferroelectric order (LRFO) and enhance ferroelectric relaxor behavior, thereby optimizing the electrical properties (such as the d ₃₃*of ∼400 pm/V and the T _C of ∼300 °C) of ternary co-doped systems. The normalized unipolar strain (S _uni/S _RT) exhibits a variation of less than 12.2% over the temperature range of 25–150 °C, while d ₃₃ at 200 °C retains 80% of its value at 25°C. Moreover, LaMnO ₃ doping leads to an increase in both depolarization temperature (T _d) and d ₃₃. Overall, this study provides an effective paradigm for balancing T _d and d ₃₃ and designing the composition of temperature-insensitive commercial piezoelectronic devices.