CAREER: Property Tailoring and Reliability in Ferroic Film Actuators

本研究解决了铁薄膜行为中尚未解决的基本问题，包括畴壁对薄膜性能的影响方式、微观结构与机电各向异性之间的相关性、薄膜应力状态的作用以及执行器装置的可靠性。将利用激光烧蚀技术制备厚度为0.1 ~ 10微米的锆酸铅和锆酸铅钛改性薄膜。最初的重点将放在开发在平面和非平面基底上的厚膜沉积条件。研究中特别感兴趣的是了解薄膜微观结构和应力分布如何调节铁电薄膜的机电各向异性。温度、偏置电场、薄膜应力和电极材料中的应力对材料性能的影响将被评估，并用于开发铁弹性畴与二维应力相互作用的模型。这些研究将与确定薄膜和厚膜致动器的主要退化和失效机制相结合。特别强调将放在确定在应力集中和裂纹产生器件几何的作用。有限元建模将用于计算几种不同致动器结构中的应力。将制定膜基致动器可接受应力集中的准则。作为本研究的附属部分，功能分级薄膜将被研究。了解薄膜铁电材料的基本特性将具有重要的科学和技术意义。此外，该项目还有一个强大的教育部分，强调新课程的开发，并专注于指导研究生，本科生和大学预科学生。首席研究员将开设“材料的光学性质与光学特性”和“电子与光子材料的性质”两门新课程。拟议的本科生和大学预科学生指导计划的基石是参与者融入正在进行的研究项目。目前还没有开设材料科学课程的4年制大学教员的教材开发等教育活动也在计划之中。＊＊＊

9502431 Trolier-McKinstry This research addresses unresolved fundamental issues in the behavior of ferroic films, including the manner in which domain walls contribute to film properties, correlation between microstructure and electromechanical anisotropy, the role of thin film stress states, and the reliability of actuator devices. Laser ablation will be utilized to prepare modified lead zirconate and lead titanium zirconate films in the range of 0.1 - 10 micrometer thickness. Initial emphasis will be placed on developing deposition conditions for thick films on planar and non-planar substrates. Of especial interest in the research is the development of understanding how film microstructure and stress distribution modulate the electromechanical anisotropy of ferroelectric films. The influence on the material properties of temperature, bias electric field, film stress, and stress in the underlying electrode material will be evaluated and utilized to develop a model for the way in which ferroelastic domains interact with two-dimensional stresses. These studies will be coupled with a determination of the principal degradation and failure mechanisms in thin and thick film actuators. Special emphasis will be placed on determining the role of device geometry in stress concentration and crack generation. Finite element modeling will be used to calculate the stresses present in several different actuator structures. Guidelines for acceptable stress concentrations in film-based actuators will be developed. As a subsidiary component of this research, functionally graded films will be investigated. %%% The understanding of fundamental features of thin film ferroelectric materials will be of scientific and technological significance. Additionally, there is a strong educational segment to this project which stresses development of new courses and a focus on mentoring graduate, undergraduate, and pre-college students. The principal investigator will develop two new courses in ''Optical Propert ies and Optical Characterization of Materials" and ''Properties of Electronic and Photonic Materials." The cornerstone of the proposed mentoring program for undergraduate and pre-college students is integration of participants into ongoing research projects. The educational activities planned also include course materials development for faculty at four year colleges currently without materials science courses. ***