SUBSTITUTION EFFECTS AND NEUTRON DIFFRACTION STUDY OF YBa_2(Cu_(0.95)M_(0.05))_3O_(7-δ)

YBa2(Cu_(0.95)M_(0.05))_3O_(7-δ) were identified as single phase with M = Ti, V, Cr, Mn, Fe, Co, N_1, Cu and Zn. Substitution of Fe, Co, Ni and Zn for Cu makes T_o, decrease significantly, while at the same content, no distructuve effect on T_c was observed in the replacement of Cu with Ti, V, Cr and Mn. The site occupation of Ti, Mn, Fe and Co ions has been investigated by using neutron diffraction technique, and strong site preference for these ions were observed. Based on these results, the two diffrent Cu sites and their relationship to the superconductivity in YBa_2Cu_3sO_(7-δ) are discussed. The substitution effect for copper on magnetic properties in YBa2(Cu_(0.95)M_(0.05))3O_(7-δ) and the correlation between magnetic and superconduc-tiviting properties are reported.