Accession Number : ADA114243

Title :   Controlled Grain Boundary Structures in Superconductors.

Descriptive Note : Final rept. 1 Jan 77-31 Dec 81,

Corporate Author : CORNELL UNIV ITHACA NY DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Kramer,Edward J

PDF Url : ADA114243

Report Date : Mar 1982

Pagination or Media Count : 15

Abstract : Theoretical work supported by this grant has lead to the concept of the specific pinning force Q and the development of new methods to sum elementary interaction forces to find Q. Pinning due to changes in transition temperature or thermodynamic critical field in thin layers (e.g., a grain boundary), is greatly reduced due to the proximity effect and the stress field interaction due to the dislocations in the grain boundary has been shown to be negligible. The crystalline anisotropy (CA) and electron scattering (ES) interactions have been computed for the first time for an arbitrary boundary. Experiments on niobium bicrystals, polycrystalline niobium thin foils doped with oxygen, lead-bismuth alloy thin films and lead-bismuth alloy films in which either lead or thallium has been allowed to diffuse down the grain boundaries and out into the grains provide evidence that confirms the predictions of the theory. These results suggest that further improvements in grain boundary pinning in the A-15 compounds, which are relatively high purity, are possible by decreasing their impurity content if that can be accomplished without decreasing their thermodynamic critical field or transition temperature.

Descriptors :   *Superconductors, *Grain boundaries, *Control, *Grain structures(Metallurgy), Molecule molecule interactions, Control, Dislocations, High rate, Purity, Niobium, Foils(Materials), Polycrystalline, Thinness, Transition temperature, Anisotropy, Crystals, Electron scattering, Oxygen, Predictions, Theory

Subject Categories : Crystallography
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE