Structure and Superconductivity of Hg Ba_2Ca_2Cu_30

Structure and Superconductivity of Hg Ba_2Ca_2Cu_30_8+\delta

Session Q09 - HTSC: STRUCTURES AND DEFECTS
Mixed session, Friday morning, March 24, 8:00
Ballroom A5, San Jose Convention Center

[Q09.01] Structure and Superconductivity of Hg Ba_2Ca_2Cu_30_8+\delta

J.L. Wagner (Department of Physics, University of North Dakota),B.A. Hunter (Australian Nuclear Science and Technology Organization, Lucas Heights Research Laboratories),D.G. Hinks,J.D. Jorgensen (Material Science Division, Argonne National Laboratory)

We have investigated the structure, defect concentration and superconducting properties of Hg Ba_2Ca_2Cu_3O_8+\delta by neutron powder diffraction, thermogravimetric analysis (TGA) and AC susceptibility. Samples with three oxygen contents, obtained through different annealing conditions, were studied with T_c 's ranging from 135 to 94 K. Two different oxygen defects sites were observed in all samples. The concentration of the variable defect site, located in the center of the Hg- O_\delta plane, is found to vary from 0.18(2) to 0.10(2) oxygen atoms per formula unit as T_c decreases from 135 to 94 K. An additional oxygen defect, presumably related to the substitution of Cu on the Hg site, is found to have a fixed concentration of \sim 0.09(2) oxygen atoms per formula unit. Experiments on the nature of Hg-1223 in the overdoped regime will also be presented.

Part Q of program listing