Grain Boundaries and Jc in High-Tc Oxide Superconductors

Superconductors are materials which carry electrical current without resistive loss below a certain critical temperature (Tc). There are many potential uses for materials that are superconducting, but until recently the Tc's of known materials were too low to be useful in large-scale applications such as power transmission. However, with the discovery of high Tc oxide superconductors, the feasibility of such projects are now being considered. The problem with the oxide superconductors is not that their critical temperature is too low (the Tc's of the oxides are almost an order of magnitude better than the metal superconductors), but rather that in bulk form their current carrying capacity (Jc) is too low. It is known that the bulk Jc is determined by intergranular conductivity. Low values for Jc may occur because of: (a) a change of stoichiometry at the grain boundaries, or (b) because of misorientation of adjacent grains. High Jc's can be achieved in thin films by texturing the material so that there are few grain boundaries across the direction of current flow but many grain boundaries perpendicular to the current flow.

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High Resolution Electron Microscopy of internal interfaces in layered materials

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100174734 ◽

1990 ◽

Vol 48 (4) ◽

pp. 320-321

Author(s):

Yoichi Ishida ◽

Hideki Ichinose ◽

Yutaka Takahashi ◽

Jin-yeh Wang

Keyword(s):

Grain Boundaries ◽

Mirror Symmetry ◽

Functional Materials ◽

High Resolution Electron Microscopy ◽

Layered Materials ◽

Plane Boundary ◽

Chemical Information ◽

Layer Plane ◽

High Tc ◽

Cubic Metals

Layered materials draw attention in recent years in response to the world-wide drive to discover new functional materials. High-Tc superconducting oxide is one example. Internal interfaces in such layered materials differ significantly from those of cubic metals. They are often parallel to the layer of the neighboring crystals in sintered samples(layer plane boundary), while periodically ordered interfaces with the two neighboring crystals in mirror symmetry to each other are relatively rare. Consequently, the atomistic features of the interface differ significantly from those of cubic metals. In this paper grain boundaries in sintered high-Tc superconducting oxides, joined interfaces between engineering ceramics with metals, and polytype interfaces in vapor-deposited bicrystal are examined to collect atomic information of the interfaces in layered materials. The analysis proved that they are not neccessarily more complicated than that of simple grain boundaries in cubic metals. The interfaces are majorly layer plane type which is parallel to the compound layer. Secondly, chemical information is often available, which helps the interpretation of the interface atomic structure.

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High Tc Oxide Superconductors

MRS Bulletin ◽

10.1557/s0883769400059479 ◽

1990 ◽

Vol 15 (6) ◽

pp. 31-33

Author(s):

M. Brian Maple

Keyword(s):

Physical Properties ◽

Energy Gap ◽

Vortex State ◽

Oxide Superconductors ◽

High Tc ◽

Superconducting Energy Gap ◽

Consistent Picture ◽

Novel Processing ◽

Processing Techniques

This issue of the MRS BULLETIN is devoted to high Tc superconductivity. It is the sequel to a previous series of articles on the same subject which appeared in the MRS BULLETIN in January 1989. While the articles in the January 1989 issue emphasized the families of high Tc superconducting oxides known at that rime, as well as novel processing techniques and thin films, the papers in this issue focus on the physical properties of high Tc oxide superconductors.The quality of polycrystalline and single-crystal bulk and thin-film materials has improved to the point where researchers can now make reliable measurements of many physical properties representative of the intrinsic behavior of these materials. As a result, a broad spectrum of important issues such as the nature of the electronic structure, the type of superconducting electron pairing, the magnitude and temperature dependence of the superconducting energy gap, the behavior of fluxoids in the vortex state, etc., can be addressed meaningfully. Presently emerging is a consistent picture of the physical properties of the high Tc oxides, which will form the foundation to eventually developing an appropriate theory for the normal and superconducting states of these remarkable materials.

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