Nanomechanics of Ferroelectric Fractures: Phase-Field Simulations and Piezoresponse Force Microscopy Characterizations

这项拨款的研究目的是阐明铁电材料的断裂，这是一个复杂的过程，涉及到纳米级裂纹扩展和铁电域转换之间的相互作用。发展了一种计算相场方法来模拟铁电材料中的裂纹扩展和磁畴转变，并将利用压电响应力显微镜来原位观察铁电材料在电、机械和热载荷下的这种微结构的演变。这两种技术将被结合起来研究各种铁电晶体和陶瓷的断裂行为，使得计算模拟和微观表征之间能够在与潜在的物理过程最相关的长度尺度上进行直接比较。铁电材料是一类重要的技术材料，广泛用作传感器、执行器、电容器和非易失性存储器，其许多应用依赖于外场触发的铁电域切换。铁电断裂过程与电畴转变密切耦合，对铁电器件的失效有重要影响。该项目将深入了解铁电材料中尚未被很好了解的复杂断裂过程，并将有助于提高铁电设备和系统的性能和可靠性。该项目还将培训研究生和本科生，改进研究生和本科课程，并为K-12学校的教师和学生提供外联活动。

The research objective of this grant is to elucidate the fracture of ferroelectrics, a complicated process that involves interplay between crack propagation and ferroelectric domain switching at nanometer scale. A computational phase-field method will be developed to simulate crack propagation and domain switching in ferroelectrics, and piezoresponse force microscopy will be applied for in-situ observation of such microstructure evolution in ferroelectrics under electrical, mechanical, and thermal loadings. These two techniques will be combined to investigate the fracture behavior of various ferroelectric crystals and ceramics, enabling direct comparison between computational simulations and microscopic characterization at a length scale that is most relevant to the underlying physical processes.Ferroelectrics is an important class of technological materials that are widely used as sensors, actuators, capacitors, and nonvolatile memories, and many of their applications depend on ferroelectric domain switching triggered by external fields. Ferroelectric fracture process is closely coupled with domain switching, and has important influences on the failure of ferroelectric devices. The project will shed insight on the complicated fracture processes in ferroelectric materials that is not well understood, and will help improve the performance and reliability of ferroelectric devices and systems. The project will also train graduate and undergraduate students, improve graduate and undergraduate curriculums, and offer outreach activities for K-12 school teachers and students.