Abstract
Along with fine grain sizes to increase the structural integrity of ceramic parts, control of the microstructure in samples of the new ceramic cuprates will be necessary to make possible experiments designed to reveal structure-property- processing relationships, i.e., relationships between microstructure, critical current density, and magnetic field. The low critical current densities of existing polycrystalline samples can originate in such properties as: (a) the critical importance of stoichiometry on a macro- and microscale, particularly with respect to stoichiometry-driven crystal defects; (b) extreme anisotropy, which necessitates percolative current paths in randomly oriented polycrystalline materials; (c) microcracking at the grain boundaries; (d) highly resistive grain boundaries, at least for some orientations; and (e) the lack of classical grain-boundary pinning phenomena, similar to that observed in lower-temperature superconductors. If stoichiometry, grain size, crystallographic texture, and, in general, ceramic microstructure can be controlled, these questions could perhaps be resolved. We believe, based on past history and present advanced ceramics processing capabilities, that the technically important properties for ceramic superconductors will be substantially improved by this approach and that, perhaps more importantly, a technology base for the manufacture of these new superconductors will be established.
Published Version
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