Determination of Atomic Scale Structure Property Relationships in High-Temperature Superconductors for Power Transmission Applications

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9803021 Browning This project will study the structure/property relationships in order to determine the optimum microstructure for the incorporation of high-TC superconductors into viable devices. The electronic conduction of these materials is extremely sensitive to atomic-scale defects that are introduced during the processing of the oxide material. The relationship between the atomic-scale defects and the electronic conduction can be determined by atomic resolution Z-contrast imaging and electron energy loss spectroscopy in the scanning transmission electron microscope (STEM). These techniques can be performed simultaneously in the STEM, with the image being used to determine the atomic structure and the spectrum being used to determine the electronic structure. Features of the spectrum can be correlated with the charge carrier concentration, allowing weak-links to be quantified on a scale below the coherence length. The atomic resolution analysis techniques will be applied to two systems that are currently being developed for power transmission and high-magnetic field applications. In collaboration with American Superconductor Corporation, a major thrust of the proposal is to investigate the properties of defects in Bi2Sr2Ca2Cu308 (2223) tapes and relate them to processing conditions. Building on an established successful collaborative program, this project will investigate the distribution of defects within the tapes and the relationship between the formation of the 2223 phase and the tape microstructure. The second goal of this proposal is to investigate the properties of YBa2Cu307 films produced on textured metal substrates. Although further from a viable product, this recently developed fabrication procedure offers a possible alternative to the 2223 tapes. Research will focus on a comparison of properties with the results from individual grain boundaries and single crystals, with the aim of determining the route to large-scale fabrication of t hese materials. %%% Since the discovery of high-TC superconductivity in the ceramic oxides, these materials have held the promise of efficient, powerful and sensitive electronic devices and power transmission wires. The results of this research will help determine the processing route to produce improved tapes suitable for commercial applications. The research will have a significant impact on the applications of high-TC superconductors. ***