From High Temperature Superconductivity to Nonmetallic behavior in fully oxygenated Nd_(1+x)Ba_(2-x)Cu_3O_y

摘要

We report the results of measurements of resistivity up to 300K, of thermopower up to 400K, on fully oxygenated, ceramic samples of Nd_(1+x)Ba_(2-x)Cu_3O_y with 0 ≤ x ≤ 0.65, characterized by x-ray diffraction and iodometric titration. The results indicate that T_c and the temperature dependence of the thermopower in "1-2-3" compounds with substitutions on Ba-site or on the chain Cu site seem to be determined by a single parameter.