The Influence of Poling Conditions on the Mechanical Properties of Ferroelectric Single Crystal PMN‐PT

ABSTRACT Relaxor ferroelectric Pb(Mg 1/3 Nb 2/3 )O 3 ‐(1‐ x )PbTiO 3 (PMN‐PT) exhibits excellent electromechanical coupling properties. During service, PMN‐PT is subjected to electromechanical loading, which may induce functional device failures, such as phase transitions, domain switching, and cracking. However, the associated damage mechanisms remain poorly understood. In this study, nanoindentation was employed to investigate the mechanical behavior and microstructural evolution of [001]‐oriented PMN‐0.28PT single crystals under alternating current‐poled (ACP), direct current‐poled (DCP), and unpoled (UNP) conditions. The results revealed that poling altered the domain‐wall state, increasing the hardness of the samples while reducing the fracture toughness. Compared with the DCP samples, the ACP samples exhibited improved piezoelectric properties along with degraded mechanical performance; furthermore, all samples exhibited a significant indentation size effect. Raman spectroscopy revealed phase transitions in the material under mechanical loading. Scanning transmission electron microscope analysis confirmed the occurrence of domain switching and a rhombohedral‐to‐tetragonal phase transition beneath the indent in the ACP samples. Furthermore, shear stress was identified as the dominant factor governing crack initiation. Based on these observations, a model describing microstructural evolution and crack propagation during mechanical loading was established. This study elucidates the microstructural evolution of PMN‐PT under mechanical loading and offers design strategies for enhancing its overall performance.