Preparation of Long Filaments of Superconducting Pb–Sn–Ge Alloy by Glass-coated Melt Spinning Method

Abstract

The melt spinning of Pb–Sn–Ge alloys with Pyrex glass was investigated as a means of producing a high temperature superconducting filament. Long filaments with T_c higher than 8.5 K of Pb_100-x-ySn_xGe_y (x≤30, y≤36) alloy were obtained from the molten state at 1500 K with a winding speed of 2.63 m/s. The filament was 20×10⁻⁶ m in diameter and had a mixed structure of lead (fcc) and germanium (diamond) phases. The germanium, lead and tin elements are homogeneously distributed in the filament.
In spite of such a hard heating treatment as heating at 673 K for 1800 s, the Pb₅₂Sn₂₀Ge₂₈ filament annealed exhibited the superconductivity with high T_c of 8.4 K and was found to be fine polycrystalline with a grain size of 2000×10⁻¹⁰ m and a ductile material with tensile strength of 54 MPa and elongation of 1.8%.