CAREER: Property Tailoring and Reliability in Ferroic Film Actuators

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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. ***