外场作用下铁电陶瓷材料裂纹尖端畴变的原位Raman光谱研究

Observation and mastering of the law of domain switching at crack tips of Vickers indent in ferroelectric materials under applied electric and stress field is crucial to investigate the mechanism of degradation and failure of these materials. Nevertheless, the current methods for such observations are only limited to theoretical speculation or ex-situ experiment. In this project, we proposed an "in-situ" technique to observe at micro scale the domain switching under applied electric or stress field with TriVista Laser Confocal-Micro-Raman Spectrometer, and build Raman spectroscopy method to quantitative characterize domaiin swtiching with in-situ observation. Based on the technique, a Vickers indent is to be first introduced in PLZT ferroelectric materials specimen and then the change of Raman spectrum associated with the domain switching arround the crack tips either by applied electric field or by stress field is to be measured and studied. Finally, mapping either for the domain switching region or for the stress field distribution around the crack tips is supposed to be obtained. The final goal of the project is aimed at providing an effective technique to quantitatively characterize the domain switching of the crack tips as well as the crack propagation so that we can find an effective route to further understand the mechanism of degradation and failure of ferroelectric ceramic materials.

掌握力电场作用下铁电陶瓷材料裂纹尖端的畴变规律对研究其疲劳失效机理具有重要的理论指导意义，目前观测裂纹尖端畴变行为的各种方法都局限于理论推测或者非原位实验观测。本研究采用三级共焦显微Raman光谱技术，探索建立外场作用下具备"原位微区观测"能力的畴变观测方法和实验技术，构筑能根据原位观测结果定量表征铁电畴变的Raman光谱分析方法。应用此技术，通过对掺镧锆钛酸铅(PLZT)多晶陶瓷材料裂纹尖端区域在力电耦合外场作用下畴变行为的原位Raman光谱观测和理论分析，获得裂纹尖端在外场作用下的畴变区和应力场分布图，探索利用Raman光谱技术研究铁电陶瓷材料裂纹尖端畴变和裂纹扩展的规律，从而为进一步理解铁电材料性能衰变机理奠定关键的科学途径。

掌握力电场作用下铁电陶瓷材料裂纹尖端的畴变规律对研究其疲劳失效机理具有重要的理论指导意义，目前观测裂纹尖端畴变行为的各种方法都局限于理论推测或者非原位实验观测。本研究自行设计和搭建外场下畴变的原位Raman观测装置,利用Raman光谱技术发展一种对铁电陶瓷材料的畴变进行原位观测的实验方法和表征技术。 采用传统固相法合成晶粒平均尺寸为5µm、四方结构的掺镧锆钛酸铅（PLZT）铁电陶瓷材料，在陶瓷表面引入维氏压痕和施加外加电场，在力电耦合作用下，利用Raman光谱技术原位观测裂纹尖端附近区域不同空间位置处的Raman谱变化，获得Raman软模E(2TO)和E(3TO+2LO)+B1的峰强随裂尖观测点空间位置的变化规律。结果表明PLZT陶瓷材料裂纹尖端在外场作用下的电致应变和畴变行为与空间位置的分布关系，并获得外场下裂纹尖端的畴变及裂纹扩展的规律，为探明铁电陶瓷材料的疲劳失效机理提供有力的理论依据。