The Study of Nb3Sn Phase Content and Structure Dependence on the Way of Ti Doping in Superconductors Produced by Bronze Route

AbstractOne of the most effective ways to increase the current-carrying ability of Nb3Sn superconductor is doping of the superconducting phase by Ti, since it leads to Hc2 increase due to the rise of Nb3Sn phase electrical conductivity in normal state, and also to acceleration of the Nb3Sn layer growing during reaction and to critical current density increasing. The investigations of structure and composition of Nb3+xSn superconducting strands by SEM, TEM and EDXS microanalysis have been carried out. The structure and composition of Nb3Sn superconducting phase of the strands after reaction at 575°C 150 h+650°C 200h have been studied. The dependence of Ti content in Nb3Sn phase from the amount of Ti introduced in Nb filaments or in bronze matrix has been also studied. It was found, that the lowest Ti content corresponds to introduction of it through the matrix doping. It has been established that Nb content in Nb3Sn essentially exceeds the stoichiometric one (3:1). The Nb3Sn lattice parameters have been defined by XRD. It was found, that the lattice parameters in the samples with Ti doped matrix were the closest to the stoichiometric Nb3Sn. The correspondence between grain morphology and composition of superconducting phase and critical current density of studied strands has been established