Thermal conductivity of composite multi-filamentary iron-based superconducting tapes

The longitudinal thermal transport properties of composite multi-filamentary iron-based superconducting tapes are studied in magnetic fields up to 9 T. The Cu/Ag tape exhibits the highest thermal conductivity kappa(4.2 K) = 440 W m(-1)K(-1)at 0 T, which remains above 100 W m(-1)K(-1)at 9 T. After applying different alloys as the outer sheath, the overall thermal conductivity is considerably decreased. We utilize the equivalent heat current circuit model to analyze the temperature dependence of kappa. It is found that there exist two sources of diffusion into the inner Ag sheath: the doped Sn from the superconducting core and the elements from the outer sheath. It results in a suppressed thermal transport ability of the Ag sheath. Our studies provide insights and precautions for conductor designs for the future applications of iron-based superconducting wires and tapes.