On the role of the reduction step in Nd Ce Cu O : 1.85 0.15 1"d y a study of thermodynamic properties and electrical resistivity at high temperature

A. SERQUIS; F. PRADO; A. CANEIRO

PHYSICA C - SUPERCONDUTIVITY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1999 vol. 313 p. 506 - 508

0921-4534

Resistivity and thermogravimetric measurements of the equilibrium oxygen partial pressure  pO2.. at 9008C have beenperformed for samples of Nd1.85Ce0.15Cu1"d Oy with nominal copper content of 0.99 and 1.01. The equilibrium pO2 . andresistivity data indicate a dependence of both properties on the nominal Cu content 1"d . of the samples. The data areanalyzed considering the existence of point defects in the cationic and anionic sublattices of the TX phase. Thesuperconducting response of samples with accurate control of copper and oxygen content is correlated with the presence ofsuch defects. Superconductivity appears suddenly in samples with 1qd)1.00 quenched at pO2. values just below theCuO–Cu2O equilibrium. The role of the ‘reduction step’ in the appearance of superconductivity is discussed in terms of twopossibilities: on one hand, the existence of randomly distributed interstitial oxygen atoms and on the other hand, the removalof microstrains present in the non-superconducting samples.