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
^-1
K
^-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.