Superconducting transition temperature of Cu-Nb microcomposites
Abstract
An experimental study of Cu-Nb microcomposites was made, its purpose being to determine the dependence of their superconducting transition temperature on the structure and the Nb content. Specimens with 20 percent Nb and with 40 percent Nb were produced. Sintered compacts were drawn into wires 3.4 to 0.16 mm in diameter. The superconducting transition temperature was determined accurately within 0.2 K by the induction method with a carbon thermometer which had been calibrated against a Ge resistance thermometer and critical temperatures of several metals and alloys as reference points. The readings are compared with those pertaining to Nb fibers 3.4 to 0.16 gmm in diameter extracted from wires of correspondingly 1000 times larger diameter. The coherence radius was determined on the basis of measurement of the electrical resistance of the Cu matrix at a temperature between 4.2 K and 50 K, which yielded 0.05 gmm at 4.2 K. The results indicate two critical temperatures with a characteristic resistivity plateau between them for specimens without residual resistivity and thus becoming perfect superconductors. They also indicate that the temperature range of superconducting transition becomes narrower with a higher Nb content, with the plateau eventually vanishing, evidently owing to a closer packing of Nb fibers.
- Publication:
-
JPRS Report Science Technology USSR Space
- Pub Date:
- February 1988
- Bibcode:
- 1988RpScT.......25K
- Keywords:
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- Copper Alloys;
- Fiber Composites;
- Niobium;
- Niobium Alloys;
- Superconductivity;
- Superconductors;
- Transition Temperature;
- Content;
- Metal Fibers;
- Solid-State Physics