Order-disorder in YBa2Cu3O7 |
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| Institution: | 1. Department of Physics, Payame Noor University, P.O.Box 19395-3697,Tehran, Iran;2. Department of Physics, Isfahan University of Technology, Isfahan, Iran;3. Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, 27606, USA;4. Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC, 27606, USA;5. Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC, 27606, USA;1. Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, Nizhny Novgorod 603950, Russia;2. Physics Department, Lomonosov Moscow State University, Leninskie Gory, 1 Moscow 119991, Russia;3. Lobachevsky State University of Nizhny Novgorod, Prospekt Gagarina, 23, Nizhny Novgorod 603950, Russia |
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| Abstract: | We summarize here results of a fairly detailed study by high-resolution electron microscopy and electron diffraction of the high-temperature superconductor YBa2Cu3O7−δ. Data from the perfect structure for (100), (110), and (001) zones indicate that the material has an oxygen-deficient perovskite structure as previously reported from X-ray and neutron diffraction studies. In some cases planar defects along (001) directions were observed. A more important observation is the existence of a phase with disorder of the Y and Ba ion positions and of an additional amorphous phase. The perfectly ordered (defect-free) phase grows from the disordered material, and the planar defects are probably due to mechanical deformation during preparation of the material. These defects probably are not related to the superconducting properties, as recently suggested. The conclusions are consistent with the commonly encountered problems in the preparation of superconductors in high yields. |
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