Near single-phase compositions in the (Hg0.65V0.35)Sr-2(Nd1-ySry)Cu2O6+delta system have been prepared in the narrow composition range 0.3 less than or equal to y less than or equal to 0.5, with a maximum T-c = 82 K observed for y = 0.5. The crystal structure of a phase with the refined composition (Hg0.60V0.40)Sr-2(Nd0.53Sr0.47)Cu2O6.94 was determined from a combination of V-51 solid state NMR and (X-ray and neutron) powder diffraction data. In this material, linear HgO22- units are partially substituted by 2 tetrahedral VO43- oxyanions, resulting in a significant distortion of the neighbouring CuO5 and SrO8+delta polyhedra. Annealing (Hg0.60V0.40)Sr-2(Nd0.53Sr0.47)Cu2O6.94 under flowing argon reduces T-c from 67 K in the as prepared material to 54 K in the annealed product; in contrast, annealing the as-prepared material under flowing oxygen does not change Tc significantly. (C) 2003 Elsevier B.V. All rights reserved.
- neutron diffraction
- crystal structure
- X-ray diffraction
- high-temperature superconductor