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Nucleation of YBa2Cu3O7 From Precursor Films Using the Barium Fluoride Process.
- Source :
- IEEE Transactions on Applied Superconductivity; Jun2005 Part 3 of 3, Vol. 15 Issue 2, p2739-2742, 4p
- Publication Year :
- 2005
-
Abstract
- Coated-conductor applications of YBCO require YBCO layers with high J<subscript>c</subscript> and a thickness of several micrometers. The barium fluoride process offers a convenient way of depositing crack-free fluorinated precursor layers up to 5 microns thick. However, converting thick precursor layers into c-axis-oriented YBCO flints is challenging due to extensive nucleation of random grains. In this paper we address this problem with both a theoretical and experimental analysis of YBCO nucleation. We utilized optical polarization contrast to observe YBCO nuclei imbedded in the precursor matrix. We observed that the nuclei density strongly depends on processing parameters, with the oxygen partial pressure being one of the strongest factors. During ex-situ processing the nuclei merge and form grains and the nuclei density is, therefore, directly related to the grain size of YBCO film. It is desirable to have a small grain structure, since large grains do not connect well and the J<subscript>c</subscript> of such a film is low. However, attempts to increase the nuclei density also generates more randomly oriented grains. Therefore the optimization of ex-situ processing is essentially finding a balance between c-axis grain density and random grain content. [ABSTRACT FROM AUTHOR]
- Subjects :
- NUCLEATION
BARIUM fluoride
OPTICAL polarization
BARIUM compounds
OPTICS
FLUORIDES
Subjects
Details
- Language :
- English
- ISSN :
- 10518223
- Volume :
- 15
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- IEEE Transactions on Applied Superconductivity
- Publication Type :
- Academic Journal
- Accession number :
- 17429924
- Full Text :
- https://doi.org/10.1109/TASC.2005.847762