Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9841954 | Physica C: Superconductivity and its Applications | 2005 | 8 Pages |
Abstract
Superconducting YBa2Cu3O7âx thin films were prepared on pure MgO and Ag/MgO substrates (without and with Ag buffer layer) using an electron beam evaporation technique. The effects of isothermal annealing temperature and Ag diffusion on the crystalline structure and some superconducting properties were investigated by X-ray diffraction, scanning electron microscopy, critical temperature, critical current density and room temperature resistivity measurements. The optimum annealing conditions causing a high degree of preferential orientation with the c-axis perpendicular to the substrates were found to be the isothermal annealing at 930 °C for 5 h. Annealing of films on Ag/MgO substrates is accompanied by Ag diffusion from the buffer layer into YBCO films. The higher rate of crystallization of the YBCO films, the higher degree of c-axis orientation, the higher dense surface morphology, the increased lattice parameter c (by â0.1%), the reduced room temperature resistivity (2-3 times), the slightly enchanced critical temperature (Tc = 92 K at R = 0) and the critical current density (Jc = 4.2 Ã 105 A/cm2 at 77 K) were observed for the Ag-doped films (on Ag/MgO substrates) in comparison with those for the undoped films (on MgO substrates). The temperature dependence of the Ag diffusion coefficient in YBCO films in the range 600-800 °C was described by the relation D = 1.9 Ã 10â6 exp(â0.73 eV/kT).
Related Topics
Physical Sciences and Engineering
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Condensed Matter Physics
Authors
O. Görür, T. KüçükömeroÄlu, C. TerzioÄlu, A. Varilci, M. AltunbaÅ,