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A reel-to-reel MOCVD system has been designed to synthesize high quality YBCO coated tapes on Ni RABiTS (Rolling Assisted Biaxially Textured Substrates). Special buffer layer stackings have been deposited to improve the quality of the superconductor. Several buffer layers architectures rose in dense YBCO films with a similar texture, but fluctuations in critical current densities (Jc) were measured. Therefore, a more accurate and detailed measurement method such as Electron Backscattered Kikuchi Diffraction (BKD) has been used to assess the crystalline quality of the stackings. The studied sequence here was NiW /NiO /YSZ /CeO2 /YBCO. The grain and the subgrain structure as well as their size and disorientation have been analysed for each layer. First on Ni tape, secondly on the protecting NiO (200) buffer layer, then on the following CeO2 (200) film. Finally, unpublished BKD diagrams of the subsequent YBCO (001) films have been reported here. The grain evolution has been successfully studied showing the buffer layer effect on the grain growth. In this work we highlight the correlation between the misorientation of the grains (inducing NiO (111) growth and cracks) and the grain boundary morphology (size, grooves). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) |
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