Anisotropic Thermal Conductivity of Silver Sheathed Bi2223 Superconducting Tape

Anisotropic thermal conductivity, κ(T), of a silver sheathed Bi2223 (Bi2223/Ag) tape was determined for three typical directions; the length (l), width (w), and thickness (t). κ(T) of the tape along the l-direction was measured directly and those along the w - and t -directions were estimated by measuring stacked samples in which several Bi2223/Ag tapes were soldered. κ(T) of the tape along the l- and w-directions was 250 W m^-1 K^-1 at 77 K and almost coincided with each other. On the other hand, κ(T) of the tape along the t-direction was about one order of magnitude smaller than those along other directions. The measured κ(T) curves were analysed using an equivalent heat current circuit. Results show that the applied heat flows through the Ag parts for three directions. The amount of the Ag parts being in the route of the heat current depends on the direction.