Studies on Superconducting V<SUB>3</SUB>Si Tapes

Abstract

V3Si superconducting tapes were prepared by the following two processes. Dipping Process (DP): a vanadium tape was dipped into a molten Cu-Si alloy bath (Cu-16, 24 and 30 at% Si) and subsequently heat treated. Composite Process (CP): a composite of Cu-Si alloy matrix (Cu-5.0 and 9.5 at% Si) and a vanadium core was rolled into a tape and subsequently heat treated. Effects of the silicon concentration in the Cu-Si alloy on the thickness of compound layers formed by the heat treatment, superconducting transition temperature Tc and critical current density Jc of the tapes were studied. V-Si alloy ingots were also prepared by arc-melting and the values of Tc were measured.In DP- and CP-specimens, V5Si3 and V3Si compound layers are formed by the reaction between the vanadium core and the silicon diffused from the Cu-Si layer. Whenever silicon concentration in the Cu-Si layer is between 5 and 30 at%, the V5Si3 layer formed in the specimen is considerably thicker than the V3Si layer. Copper scarecely dissolves either in V5Si3 or V3Si and is not effective for enhancing the formation of V3Si unlike the case of the formation of V3Ga. Tc observed in DP-and CP-specimens is quite the same as that observed in the arc-melted specimen. Jc of the V3Si layer decreases with the increase of heat treatment temperature probably due to the grain growth of the compound. Critical current of DP-and CP-V3Si tapes are nearly one order of magnitute smaller than that of V3Ga tapes made by similar processes.