Phase Relationships and Phase Formation in the System BaF2-BaO-Y2O3-CuOx-H2O

Published

January 1, 2002

Author(s)

Winnie K. Wong-Ng, Lawrence P. Cook, J Suh, Igor Levin, Mark D. Vaudin, Ron Feenstra, James P. Cline

Abstract

The interplay of melting equilibria and reaction kinetics is important during formation of the Ba2YCu3O6+x (Y-213) phase from starting materials in the quaternary reciprocal system Ba,Y,Cu//O,F. For experimental investigation of the process we are using a combination of differential thermal analysis (DTA) for study of the melting equilibria and in-situ high-temperature x-ray diffraction (HTXRD) for study of the phase formation and reaction kinetics. DTA investigation of compositions spaced along compositional vectors extending from the oxide end to the fluoride end of the reciprocal system have given evidence of low melting liquids (~600 C) near the fluorine rich end. Work is continuing to determine whether similar events observed in the interior of the system also indicate low temperature liquids, and on the extent to which low-melting liquids could be involved in Y-213 phase formation. HTXRD investigations have been initiated on the conversion of 0.3 m and 1.0 m thick precursor films to Y-213 as water is introduced. Results indicate continued study using this method is warranted for determination of the phase formation sequence of the Y-213 superconductor. Also, the thickness of the films is important in determining how the Y-213 film grows: a 0.3 m film showed mainly (001) texture, whereas a 1.0 m film showed a greater extent of (100) texture. While the HTXRD method cannot directly show the presence of liquid, we are working to combine DTA and HTXRD data for a unified picture of how Y-213 phase formation progresses in the ex-situ process.

Proceedings Title

Materials for High-Temperature Superconductor Technologies, Symposium E | | | Materials Research Society

Volume

689

Conference Dates

November 1, 2001

Conference Title

Materials Research Society Symposium Proceedings

Pub Type

Conferences

Keywords

BaF₂-BaO-Y₂O₃-CuO_x-H₂O, high T_c Superconductors, low-temperature melts, phase equilibria, phase formation

Citation

Wong-Ng, W. , Cook, L. , Suh, J. , Levin, I. , Vaudin, M. , Feenstra, R. and Cline, J. (2002), Phase Relationships and Phase Formation in the System BaF₂-BaO-Y₂O₃-CuO_x-H₂O, Materials for High-Temperature Superconductor Technologies, Symposium E | | | Materials Research Society (Accessed April 26, 2024)