AC Complex Susceptibility of Superconducting La–Sr–Cu–O and Y–Ba–Cu–O Systems

The complex susceptibility x'-ix" of the superconducting La–Sr–Cu–O and Y–Ba–Cu–O systems were measured together with their electrical resistance. The recent best specimen of Y1Ba2Cu3O7-α shows the complete Meissner effect in the temperature width less than 1.7 K at Tc=91 K (mid-point). This specimen was found to be distorted to the orthorhombic structure by about 1.5%. This specimen was studied both in powdered and in recompressed into a pellet style. It is found that the semiconductive behavior in the electrical resistance comes from the grain boundary. DC susceptibility and ESR measurements of this specimen were carried out.