Morphology and Structure of Diffusion Layers in Nb3Sn-Based Superconductors of Different Geometry

Abstract

The evolution of structure and morphology of superconducting Nb3Sn layers forming under various regimes of the diffusion annealing in multifilamentary Nb/Cu–Sn superconductors of different design is briefly reviewed based on the authors’ (with their coauthors) original studies and the available publications. Different modes of the solid-state diffusion formation of the superconducting phase are compared. Possible mechanisms of the Nb3Sn nucleation upon the diffusion reaction of the Nb filaments and bronze matrixes are discussed. The effects of different doping elements, especially Ti, on the formation of the superconducting phase, its structure and morphology, and, consequently, on the current-carrying capacities of multifilamentary Nb3Sn-based wires are considered. Special attention is paid to the effect of the mode of Ti doping, the content of this alloying element and the regimes of the diffusion annealing on the structure, morphology and resulting performance of the bronze-processed wires with coupled Nb filaments worked out at Bochvar Institute of Inorganic Materials for the creation of International Thermonuclear Experimental Reactor.