M.S. (Master of Science)
Department of Physics
High temperature superconductivity; Copper oxide superconductors; Superconductivity; Solid state chemistry
The La[sub 2-x]Ca[sub 1+x]Cu[sub 2]O[sub 6+y] (0212) material, having the simplest double copper oxygen plane structure common to all high-T[sub c] superconductors, was synthesized in oxygen using pressures up to 600 bar and temperatures up to the melting point. Samples with 0 5 x < 0.5 synthesized in air usually contained a small amount of impurities and were not superconducting. Superconductivity was observed only for samples synthesized under high oxygen pressure and temperatures above 900°C. The range of single phase solid solutions depended on synthesis temperature and was the largest (0.1 £ x £0.3) at 1180°C. The crystal structure was studied by x-ray and neutron powder diffraction. The M(l) site was occupied by Ca atoms only, Ca substitution for La went into M(2) site. There was oxygen deficiency for samples synthesized in air. Oxygen content was increased after high pressure synthesis. The superconducting properties were determined by DC resistivity and AC susceptibility techniques. The highest T[sub c](10%) for a single-phase 0212 material was found to be about 60 K for a sample with x = 0.18, which was post-annealed in oxygen after high pressure synthesis.
Zhang-McCoy, Xiuqun, "Synthesis, structure and properties of La[sub 2-x]Ca[sub 1+x]Cu[sub 2]O[sub 6+y] high-temperature superconductors" (1993). Graduate Research Theses & Dissertations. 5195.
Northern Illinois University
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