Abstract
We report the results of measurements of resistivity up to 300 K and of thermoelectric power up to 400 K on ceramic samples of Nd1+xBa2−xCu3Oy with 0 ≤ x ≤ 0.65. The samples were fully oxygenated; they were characterized by x-ray diffraction and iodometric titration. The results are compared with data from literature reporting on effects of substitutions on the Ba site in 1–2–3 compounds and with our earlier experiments on substitution of Co for chain Cu. The focus is on the metal-nonmetal transition and on the nonmetallic regime in all these systems. Tc and the temperature dependence of S close to the metal-nonmetal transition and in the nonmetallic state seem to be determined by a single parameter, irrespective of the nature of the dopant. This result and its implications on the electronic structure of Rba2Cu3Oy (R = Y, or lanthanide ion) will be discussed.
Published Version
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