GOALI: Investigating the Defect Structures in Superconducting Materials for Power and Electronic Applications

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NON-TECHNICAL DESCRIPTIONThe discovery of high-Tc superconductivity in the mid-80s held the promise of new, efficient, powerful, and sensitive electronic devices and power transmission wires. However, the sheer complexity of the materials issues related to these perovskite ceramics has so far severely limited the realization of this technology. Of particular importance for all applications involving superconductors are the properties of grain boundaries and other structural defects. In this program, the aim is to use advanced methods of structural and electronic characterization in state-of-the-art transmission electron microscopes to first understand and then potentially remove the deleterious properties of these defects. This work involves a strong collaboration with the US leader in superconductor technology, American Superconductor, and includes significant training of graduate students in both the most advanced characterization methods and their application to industrial research and development. An additional benefit of this program will be the establishment of a remote access collaboratory, allowing the microscope methods to be used off-site for research by anyone in the US and in particular, for outreach programs administered through the established Nanomaterials for the Environment, Agriculture and Technology (NEAT) initiative at UC-Davis.TECHNICAL DESCRIPTIONIn this program, it is proposed to investigate the structure-property relationships at grain boundaries in several high-Tc systems using a combination of atomic resolution Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM). These correlated techniques have been shown previously to provide accurate information on the link between structure, composition, and the local carrier concentration (which is related to the transition temperature, Tc, and the critical current, Jc). The current research program will take the experiments an important step further by utilizing unique experimental facilities (aberration corrected microscopes, monochromated microscopes and in-situ stages) to perform the atomic scale measurements both at elevated and lowered temperatures (i.e. below Tc) and in an ambient environment. These experiments will allow the effect of temperature (processing) history on the boundary properties to be characterized in the superconducting state. The program aims to work on three classes of materials at various stages of commercial development; primarily YBaCuO coated conductors, and also BiSrCaCuO wires and MgB2. Each of these systems presents their own experimental challenge, that range from determining the carrier interactions at grain boundaries to understanding the formation of the superconducting phases during heat treatments. Combining these studies into a correlated program with American Superconductor will develop a complete understanding of superconducting phenomena and allow these developments to be rapidly incorporated into new materials processing routes.