Manipulation of perovskite dielectrics with high electric fields and large strains

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NON-TECHNICAL DESCRIPTION:It is a persistent and important challenge to achieve precise, reproducible, and dynamically adjustable control of materials with applications in electronics, sensing, and clean energy. Electric fields can be useful in this respect because they can produce dramatic and surprising changes in the electronic and structural properties of these materials. New technologies have resulted in the capability to apply large electric fields to very thin layers without destroying them, yielding large but not yet understood effects. This project probes the structural changes induced in thin films of a particular class of materials based on metal complex oxides. Experiments are being conducted using X-ray scattering, precisely characterizing the crystallographic structure in applied fields. Undergraduates and graduate students are involved in experiments at national X-ray scattering facilities and in the interpretation of the experimental results using theoretical calculations. Outreach activities based on the concepts in this project bring concepts related to how the atomic-scale structure of materials is modified by electric fields to wide audiences, including through the creation of on-line structural models.TECHNICAL DETAILS:High electric fields promise to provide a new degree of freedom in studying and ultimately controlling and exploiting structural phenomena in perovskite oxide materials. High fields have the potential to induce structural phase transitions, to modify the structural symmetry, and to increase the importance of electrostriction, a largely negligible effect at low electric fields. This project uses newly developed time-resolved X-ray microdiffraction characterization techniques to probe the properties of perovskite complex oxides in high electric fields and at large strains. Experiments are underway to examine the dynamics of recently reported electric-field-driven structural phase transitions between rhombohedral and tetragonal phases, probe the relationship between piezoelectricity and crystallographic symmetry in superlattices, and explore the limits of electrostrictive distortion in complex oxide dielectrics. The project is preparing undergraduates and graduate students for careers in science and technology and exposing them to research at national X-ray scattering facilities. The atomic structure of these complex oxide materials and the structural phenomena studied in this project are presented to broad audiences using a series of interactive on-line structural models.