Texture Analysis of Coated Conductors by Micro-Raman and Synchrotron x-ray Diffraction
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Texture Analysis of Coated Conductors by Micro-Raman and Synchrotron x-ray Diffraction Teresa Puig, Anna Puig-Molina1, Narcís Mestres, Harm Van Seijen1, Francesc Alsina, Juan C. González, Xavier Obradors, Heinz Graafsma1, Alexander Usoskin2 and Herbert C. Freyhardt2 Institut de Ciència de Materials de Barcelona-CSIC, Campus UAB, 08193 Bellaterra, Spain 1 European Synchrotron Radiation Facility, BP. 220, 38043 Grenoble, France 2 Zentrum fuer Funktion Wekstoffe, Windausweg 2, D-37073 Goettingen, Germany ABSTRACT Two novel complementary and non-destructive techniques for texture analysis of YBCO coated conductors are presented. Micro-Raman (µ-Raman) spectroscopy enables an easy analysis of the film homogeneity by determining the distribution of a- and c-oriented grains within the tape with a 1 µm spatial resolution and acquisition times of 5 min/spot. In addition, synchrotron x-ray diffraction analysis in transmission geometry and 2D detectors enables, with acquisition times of 100 ms, simultaneous observation of a- and c- crystallites and in-plane textures of substrates, buffers and superconducting layer. Thus, opening the field of this technique to in-situ analysis of epitaxial growth of coated conductors prepared by ex-situ processes. Results from these two techniques for stainless steel tapes buffered with IBAD-YSZ and coated with PLD-YBCO are analyzed.
INTRODUCTION The achievement of a high degree of biaxial crystalline texture has been found to be a prerequisite for high critical current YBCO conductors [1]. Conventionally, the crystalline texture is determined ex-situ by x-ray diffraction in reflection geometry, however, it would be very appealing for the development of ex−situ growth processing methodologies, such as BaF2 evaporation or solution deposition techniques, to develop texture characterization techniques which can analyze in-situ the growth process. In addition, understanding the processes governing the formation of c-axis and a-axis crystals is an important issue since the formation of these 90º grain boundaries may strongly deteriorate the critical currents [2]. For this purpose, in-situ high energy synchrotron X-ray diffraction can be carried out in transmission geometry. In the present work, we analyze the capability of this technique, and we show its complementarity with microRaman spectroscopy, which enables spatially resolved measurements for crystalline texture and quantitative estimation of grain orientation. The samples chosen for our work were YBCO coated conductors deposited by PLD on YSZ – IBAD buffers grown on polycrystalline stainless steel substrates [3].
EXPERIMENTAL DETAILS µ-Raman and Synchrotron radiation diffraction techniques have been used to analyze the outof-plane and in-plane texture of 1 m YBCO coated conductor samples prepared by a reel-to-reel II5.6.1
technique. About 1 µm thick YBCO layers were evaporated by laser ablation on stainless steel substrates upon deposition of ~1 µm thick IBAD layers of YSZ. Detailed information on sample preparation is published elsewhere
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