Thermal Conductivity of YBCO Coated Conductors Reinforced by Metal Tape

We have measured the thermal conductivity, κ(T), of YBCO coated conductors (YCCs) reinforced by Cu or CuNi tape. κ(T) of YCC reinforced by Cu tape with 100-300 μm in thickness, YCC-Cu, was 250-400 W m^-1K^-1 at 77 K, which depended on the thickness of Cu tape and was roughly one order of magnitude larger than that of the bare YCC. On the other hand, κ(T) of YCC reinforced by CuNi tape of 300 μm thickness, YCC-CuNi, was comparable to that of the bare YCC except for the low temperatures. The contribution of each reinforcing material to the thermal transport was estimated by analyzing the measured κ(T) using an equivalent heat current circuit. The applied heat flows mainly through the Cu tape for the YCC-Cu tapes and through both CuNi tape and stabilizing Ag layer for the YCC-CuNi tapes, respectively. Phonons cannot be ignored as thermal carriers in YCC-CuNi tapes.