Structural and physical properties of the Metal (M) substituted YBa sub 2 Cu sub (3-x) M sub x O sub (7-y) Perovskite.

The mixed YBa sub 2 Cu sub (3-x) M sub x O sub (7-y) (M=Ni, Zn, Fe, Co and Al) phases have been characterized for their structural, magnetic and superconducting properties. The oxygen content in these phases is dependent on the nature and the amount of doping, especially for Co and Fe. The material remains orthorhombic when Cu is replaced by Ni or Zn whereas it evolves to tetragonal symmetry for the Fe, Co and Al doped compounds when x exceeds 0.05. Evidence for the major substitution of Co in the Cu-O chains only is obtained by means of thermogravimetric analysis and neutron diffraction measurements. The room temperature Mossbauer spectra of the Fe doped compounds consist of three doublets; their site assignments are proposed. DC resistance and AC susceptibility have shown that both magnetic and diamagnetic ions destroy T sub c in a similar manner.