Sixth DOE/BES Information Meeting on High T c Superconductors Discusses Search for Higher Critical Current
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Sixth DOE/BES Information Meeting on High Tc Superconductors Discusses Search for Higher Critical Current Douglas K. Finnemore and Ellen O. Feinberg The discovery of new materials and the search for higher critical currents were the main topics of the Sixth U.S. Department of Energy High Temperature Superconductivity Information Meeting. Sponsored by the Materials Science Division of the Office of Basic Energy Sciences of DOE, the meeting was one of a series that is providing a forum for coordinated high Tc Information exchange among DOE-sponsored laboratory programs. Over 75 scientists attended the Conference at the Arnes Laboratory, Arnes, Iowa, and at least 215 additional researchers at 17 sites participated via the NTU/AMCEE (National Technical University/Association for Media-Based Continuing Education for Engineers) satellite network. The meeting was divided into five panels: (1) the Status of the theory, (2) synthesis and structure of new materials, (3) properties of new materials, (4) role of flux creep and grain boundaries in critical currents, and (5) weak link effects in critical currents. The panels began following a brief, untelevised session. In order to accommodate the requirements of the teleconference, each panel consisted of a series of 10-20 minute presentations followed by a brief question-and-answer session. The television audience called in questions to which the panelists responded. Highlights of the meeting include a report by Dave Hinks (Argonne National Laboratory) of a new protocol for doping (BaK)Bi03, and a report by Duane Dimos (IBM Yorktown) of the critical current of isolated grain boundaries.
MRS BULLETIN/OCTOBER1988
Panel I—Status of the Theory Vic Emery (Brookhaven National Laboratory) gave an overview of new materials and the implication of these discoveries for theory. He divided these materials into two groups. The first was highly anisotropic materials based on Bi and Tl, which have structures dominated by copper-oxide sheets and transition temperatures up to 125 K. The second was isotropic perovskite structures based on (BaK)Bi03, with Tc
around 30 K. He outlined a series of careful experiments that wül be needed to lay the groundwork for a füll understanding of these two classes of materials. Dwight Jennison (Sandia National Laboratories) presented a more detailed Cluster calculation of Screening of localized holes on the oxygen sites. Within this model, weak Screening leads to localization and an electronically driven pairing. Panel II—Synthesis and Structure of New Materials Charles Torardi (Dupont Corporation) presented an overview of synthetic techniques for a wide ränge of new materials. He emphasized techniques to control the high vapor pressure of some components and methods to accurately control doping. He then briefly outlined the possibility of getting four or five copper-oxide sheets per unit cell. Bruno Morosin (Sandia National Laboratories) discussed the role of cation disorder, the effect of oxygen vacancies, and the broad implications of structural changes.
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