Thermal Conductivity and Thermal Dilatation of Commercial BSCCO (DI-BSCCO) Tapes

We have measured the thermal conductivity, kappa(T), and thermal dilatation, deltaL(T)/L(300 K) , as a function of the temperature for four types of commercial (Bi,Pb)₂Sr₂Ca₂Cu₃O_10+x (Bi2223) tapes sheathed with silver-alloy (DI-BSCCO). kappa(T) of three Bi2223/Ag-alloy tapes [Type H, Type HT, and Type AC] shows a similar temperature dependence, but the absolute value of the kappa(T) depends on the structure and volume ratio of sheath part. The sheath material of types H and AC is a silver-alloy and that of type HT consists of both silver-alloy and stainless steel tapes. Type AC has the twisted Bi2223 filaments. On the other hand, kappa(T) of the Bi2223/Ag-5.4wt%Au-alloy tape [Type G] shows very low value and decreases monotonically with decreasing temperature. Near 77 K, the absolute values of the type H and type G tapes were about 260 W m^-1 K^-1 and 80 W m^-1 K^-1, respectively. deltaL(T)/L(300 K) of four tapes decreases with decreasing temperature, and approaches -0.31 ~ -0.38% below 25 K for all the tapes.