Strain-induced lead-free morphotropic phase boundary

作者：Reza Namdar Ghanbari, Harikrishnan KP, Kinnary Patel, Hua Zhou, Tao Zhou, Rui Liu, Liyan Wu, Aarushi Khandelwal, Kevin J. Crust, Sankalpa Hazra, John M. Carroll, Cedric J. G. Meyers, Jiayue Wang, Sergey Prosandeev, Huimin Qiao, Young‐Hoon Kim, Yoji Nabei, Miaofang Chi, Dali Sun, Nina Balke, Martin V. Holt, Venkatraman Gopalan, Jonathan E. Spanier, David A. Muller, L. Bellaïche, Harold Y. Hwang, Ruijuan Xu · 发表于：Nature Communications · 年份：2025 · DOI：10.1038/s41467-025-63041-w · 被引用次数：10 · 研究领域：Ferroelectric and Piezoelectric Materials、Acoustic Wave Resonator Technologies、Ultrasonics and Acoustic Wave Propagation

Enhanced susceptibilities in ferroelectrics often arise near phase boundaries between competing ground states. While chemically-induced phase boundaries have enabled ultrahigh electrical and electromechanical responses in lead-based ferroelectrics, precise chemical tuning in lead-free alternatives, such as (K,Na)NbO3 thin films, remains challenging due to the high volatility of alkali metals. Here, we demonstrate strain-induced morphotropic phase boundary-like polymorphic nanodomain structures in chemically simple, lead-free, epitaxial NaNbO3 thin films. Combining ab initio simulations, thin-film epitaxy, scanning probe microscopy, synchrotron X-ray diffraction, and electron ptychography, we reveal a labyrinthine structure comprising coexisting monoclinic and bridging triclinic phases near a strain-induced phase boundary. The coexistence of energetically competing phases facilitates field-driven polarization rotation and phase transitions, giving rise to a multi-state polarization switching pathway and large enhancements in dielectric susceptibility and tunability across a broad frequency range. Our results open new possibilities for engineering lead-free thin films with enhanced functionalities for next-generation applications. The authors demonstrate strain-induced morphotropic phase boundary-like nanodomains in lead-free NaNbO3 thin films, enabling multi-state switching and large enhancements in dielectric susceptibility and tunability over a broad frequency range.