INFLUENCE OF THE REDUCTION AND OF THE OXIDATION ON ND(2-X)CE(X)CUO(4+DELTA)

In order to obtain superconductivity in RE2CuO4 (RE rare earth : Pr, N d, Sm, Eu) all compounds have to be doped with Ce substituting the RE, additionally it is necessary to anneal the samples at high temperatur e in a reducing atmosphere. Single crystal neutron and X-ray diffracti on was used to study the reduction effects in Nd2-xCexCuO4+/-y, (with x=0 and 0.15). The study of as grown, reduced and oxygenated samples i ndicate different structural changes in doped and undoped samples. The oxygen loss in the CuO2 planes of Nd2CuO4-y (y=0.056(8)) and of Nd1.8 5Ce0.15CuO4-y (y=0.000(8)) is obtained from structural refinements of the same single crystals before and after reduction, and after reoxida tion. The second oxygen site remains unchanged with respect to thermal parameters and occupancy. The strong changes in extinction effects of the samples were observed to be reversible with oxidation/reduction t reatments.