正方晶YBa2Cu3O6.76の構造および物性に与える酸素アニールの効果

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The phase change of the non-superconducting tetragonal- I phase(YBa2Cu3O6.76) by annealing in oxygen atmosphere was studied.Tetragonal-III(YBa2Cu3O7.06) and Orthorhombic-III(YBa2Cu3O7.11) are formed under the annealing conditions:(1)900°C×2hr+400°C×10hr and (2)400°C×100hr, respectively.Examination with a high resolution electron microscope revealed that T- I has homogeneous tetragonal structure without any microdomain structure. However T-III has partial inhomogeneity which is caused by microdomain structure or twinning. O-III has homogeneous orthrhombic structure with slightly different a and b axes. T-III and O-III show the superconducting transition at 92K and 60K, respectively as obtained by magnetic susceptibility measurements. The set of results supports the importance of ordering of oxygen in the Cu(1)-O chain site for the occurrence of the high temperature superconductivity in the Y-Ba-Cu-O system.
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