Effects of metal substitution on superconductivity and crystal structure of HgBa2CuO4+delta

High-T-c superconducting oxides with nominal compositions of HgBa2Cu1-xMxO4 +delta (M = Fe, Co, Ni, Zn and Mg, x = 0-0.03) were prepared, and crystal s tructure and substitution effects on superconducting properties were studie d using X-ray powder diffraction, susceptibility and resistivity. Almost al l single-phase samples were obtained for M = Fe, Co, Zn and Mg, while impur ities such as Ni3Ba3O8 were detected for M = Ni. A significant decrease in T-c and an increase in lattice parameter a for the samples with Zn and Mg i ndicated that these metals were successfully substituted for Cu. On the oth er hand, there was no remarkable change in T-c for the sample with Fe and C o, which suggests a possibility of substitution for Hg. Zn- and Mg-substitu tion effects on superconductivity were discussed from the viewpoint of stru ctural change, in comparison with the cases of La2-xSrxCuO4 and YBa2Cu3O6+d elta. (C) 2001 Elsevier Science B.V. All rights reserved.