Preparation, structure and superconductivity of Ru1222 and Ta-doped Ru1212

The samples Ru3-chiTachiSr2GdCu2Ogamma (Ru1212) (chi = 0. 0.05, 0.15) and R uSr2Gd1.4Ce0.6Cu2Ogamma (Ru1222) were syn thesized by solid-state reaction. X-ray diffraction data indicate that all samples are in a single phase. Ta doping apparently suppresses superconductivity for Ru1-chiTachiSr2GdCu2Oga mma system. The effect of the annealing procedure on superconductivity is s ignificant for Ru1212 system. Oxygen content is crucial to superconductivit y accompanied by an apparent change of lattice parameters for Ru1222. the i ncrease of oxygen content results in a decrease of lattice pa rameters and an increase of T-c. (C) 2001 Elsevier Science B.V. All rights reserved.