THE INFLUENCE OF LITHIUM INTERCALATION AND IODINE ON THE ELECTRICAL-PROPERTIES OF THE SUPERCONDUCTOR ND1.82CE0.18CUOZ

As-prepared Nd1.82Ce0.18CuOz pellets treated by electrochemical lithiu m intercalation and iodine vapour were studied. It was found that the sample Li0.06Nd1.82Ce0.18CuOz intercalated by lithium at 705-degrees-C , using LiF/KF melt electrolyte, became superconductive at T(c) = 23.5 K. The mechanism is considered to be that lithium has been inserted i nto the interstitial site near the Cu-O square and has donated its ele ctron to the CuO2 plane, while the extra oxygen atom has been removed. The insertion of lithium using LiClO4 polypropylene carbonate electro lyte cells at room temperature was very slow and no superconductivity was observed. For these samples with lithium inserted at room temperat ure and then annealed at 900-degrees-C in air, the defect oxygen atoms can be introduced into the structure along with lithium as shown by t he increase of resistivity with the lithium amount. The samples treate d with iodine at 200-degrees-C showed a resistivity drop between 9.9 a nd 13.9 K, which might indicate superconductivity in a small portion w ith possible composition Nd1.82Ce0.18CuOz-yIy. Combined with the resul ts of the luminescence spectra, the mechanism of deoxygenation can be considered as the delocalization of the doped electrons in the crystal .