Kenichi Kawaguchi1, Sang-Soo Oh2, Shojiro Ochiai3 and Kozo Osamura3
1Graduate Student, Kyoto University, Kyoto. Present address: Tsukuba Laboratory, Sanyo Co. Ltd., Tsukuba
In order to investigate the mechanism of crystal growth and superconducting properties of V3Ga compound as well as the influence of third element additions, the sandwich-type diffusion couples, which consisted of Cu-Ga or Cu-Ga-M (M=Al, Ti) alloy sheets and pure V foil inserted between them, were prepared.
The couples were heat-treated at temperatures between 923 and 1073 K to form the V3Ga compound.
The growth rate of the compound layer was enhanced by the Al addition, where V3Ga grains tended to become columnar when the specimen was annealed for a long time. On the other hand, a fine equiaxed grain structure was formed for the specimen with Ti addition by any annealing treatment.
Considering the time-exponent in the function, d=ktn, where d and t are the layer thickness and the time, respectively, it was suggested that the diffusion of Ga in the V3Ga compound controls the overall rate of crystal growth.
The relation between the maximum global pinning force, Fp,max and the grain size was investigated. It was concluded that Fp,max depends on the reciprocal grain size for the specimen without the third element.
The critical current density at a high magnetic field was found to be improved by the Al addition owing to the so-called peak-effect.
vanadium three gallium, crystal growth, superconducting property, layer thickness, diffusion of gallium, third element, critical current density, global pinning force
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