Some thermal and electrical properties of the high-Tc superconductors Y-Ba-Cu and Bi-Sr-Ca-Cu oxides

The heat capacity, Crho, has been measured in the range of 0.4 to 20 K and the linear thermal expansivity, α, in the range 2 to 283 K of YBa2Cu3O7. Below 4 K Crho exhibits a T-term (∼ 7.5 T mJ/mol.K), but in general both Crho(T) and --(T) have magnitudes and T-dependences that are not very different from other ceramics. The electrical resistance of YBa2Cu3O7 and Bi2Sr1.7CaCu2O8 samples have been measured in the range 20 to 120 K and in magnetic fields of up to 7 T. In all cases the value of Tc is highly sensitive to the applied magnetic field. The upper critical field, Bc2(0), is estimated to be 68.5 T for YBa2Cu3O7 and 55 T for Bi2Sr1.7CaCu2O8