Oxygen content influence in the superconducting and electronic properties of Nd1.85Ce0.15Cu1.01Oy ceramics

Superconducting and electronic properties of Nd1.85Ce0.15Cu1.01Oy. ceramic samples have been studied as a function of the oxygen content. It has been observed that values of oxygen content 'y' above those corresponding to the CuO-Cu2O equilibrium partial oxygen pressure destroy superconductivity. On the other hand, for lower oxygen contents, resistivity and magnetic superconducting transitions are present with critical temperature values up to 20 K. The normal state Hall effect has also been measured presenting a negative R-H coefficient in all the samples. For superconducting samples, R-H is not significantly dependent on the oxygen content value, In addition, the Hall coefficient is almost temperature independent in these samples. It is in contrast with some of the non-superconducting samples where the absolute value of R-H increases as T decreases. These results reveal that, for samples obtained by annealing below the CuO-Cu2O equilibrium partial oxygen pressure, the enhancement of superconducting properties as oxygen is reduced is not produced by a change in the carrier density, pointing then to a structural ordering effect as an explanation. (C) 2001 Elsevier Science B.V. All rights reserved.