THE CRYSTAL STRUCTURES OF SOME TRANSITION METAL STABILISED MERCURY CUPRATE SUPERCONDUCTORS

摘要

The synthesis, crystal structures and superconducting properties of three families of transition metal stabilised mercury cuprates are discussed. The crystal structures of (Hg{sub}0.60V{sub}0.40)Sr{sub}2(Nd{sub}0.53Sr0.47)Cu{sub}2O{sub}6.94, (Hg{sub}(0.78)Re{sub}0.22)Sr{sub}2Nd(o.59Ca{sub}0.41)Cu2O6.88 and (Hgo.75Moo.25)Sr2CuO4.6 were determined from Rietveld analysis of X-ray and neutron powder diffraction data. These data demonstrate that the linear HgO{sub}2{sup}(2-) units in (Hg{sub}0.60V{sub}0.40)Sr{sub}2(Nd{sub}0.53Sr{sub}0.47)Cu{sub}2O{sub}6.94, (Hgo.78Reo.22)Sr{sub}2Nd(o.59Cao.41)Cu2O{sub}6.88 and (Hgo.75Mo{sub}0.25)Sr{sub}2CuO{sub}4.6, are partially substituted by tetrahedral VO{sub}4{sup}(3-), octahedral ReO{sub}6{sup}(6-) and tetrahedral MoO{sub}4{sup}(2-) species, respectively. Hole doping in these systems arises from a combination of oxyanion substitution, cation substitution and intercalation of labile oxygen anions.