Flux Pinning and Critical Currents in A-15 Superconductors.
Abstract
The relationship between processing, microstructure, and properties was studied for A-15 compounds in multifilamentary composites produced by solid-state diffusion and in thin-film samples produced by vapor deposition. Grain sizes of A-15 superconducting compounds were measured by transmission electron microscopy of multifilamentary composites reacted at various temperatures. Critical current densities at 4.2 K and fields up to 6 T were found to be similar for niobium-tin, vanadium-gallium, and vanadium-silicon of the same grain size. Study of the Cu-V-Si phase diagram led to the production of improved multifilamentary vanadium-silicon conductors. The effects of various alloying elements on A-15 layers produced by solid-state diffusion were studied. The most promising new observation was that tantalum can be incorporated into niobium-tin reaction layers, leading to an enhancement of critical currents at high fields. The critical temperature of vapor-deposited, niobium-germanium films has been studied as a function of deposition rates, flux stoichiometry, substrate temperature, and, especially, gas composition. Introduction of controlled levels of oxygen has been found to expand the range of Nb-Ge flux ratios which yield high critical temperatures. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1978
- Accession Number
- ADA052618
Entities
People
- J. D. Livingston
- R. A. Sigsbee
Organizations
- General Electric