Heat treatment influence on the superconducting properties of nanometric-scaleNb3Sn wires with Cu–Sn artificial pinning centers

Abstract

Since the discovery of Nb3Sn superconductors many efforts have been expended to improve the transportproperties in these materials. In this work, the heat treatment profiles forNb3Sn superconductor wires with Cu(Sn) artificial pinning centers (APCs) with nanometric-scalesizes were analyzed in an attempt to improve the critical current densities and uppercritical magnetic field. The methodology to optimize the heat treatment profiles in respectto the diffusion, reaction and formation of the superconducting phases is described.Microstructural characterization, transport and magnetic measurements were performed inan attempt to relate the microstructure to the pinning mechanisms acting in thesamples. It was concluded that the maximum current densities occur due to normalphases (APCs) that act as the main pinning centers in the global behavior of theNb3Sn superconducting wire. The APC technique was shown to be very powerful because it permittedmixing of the pinning mechanism. This achievement was not possible in other studies inNb3Sn wires reported up to now.