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Title: Characterization of Phase Evolution in YBCO Coated Conductors Produced by the Ex Situ BaF 2 Process

Abstract

Raman microprobe spectroscopy and scanning electron microscopy were used to study the initial nucleation and growth of YBCO in thick precursors by the BaF2 ex situ process. For quenched films of 2 mum thickness, the data indicate a low density of c-axis nuclei near the substrate, apparently due to a reduced oxygen concentration deep inside the precursor layer. Significant non c-axis growth was also observed; the majority of this material nucleates away from the substrate. Measurement of the conversion rate by in situ XRD for films in the range 0.2-2 {micro}m suggest a weak thickness dependence.

Authors:
 [1];  [1];  [1];  [1];  [2];  [2];  [3]
  1. ORNL
  2. Argonne National Laboratory (ANL)
  3. University of Wisconsin, Madison
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
OE USDOE - Office of Electric Transmission and Distribution
OSTI Identifier:
931681
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: Applied Superconductor Conference, Seattle, WA, USA, 20060827, 20060901
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; YTTRIUM OXIDES; BARIUM OXIDES; COPPER OXIDES; NUCLEATION; CRYSTAL GROWTH; PRECURSOR; PHASE STUDIES

Citation Formats

Feenstra, Roeland, List III, Frederick Alyious, Zhang, Yifei, Christen, David K, Maroni, Victor A., Miller, D. J., and Feldmann, D. M. Characterization of Phase Evolution in YBCO Coated Conductors Produced by the Ex Situ BaF2 Process. United States: N. p., 2007. Web.
Feenstra, Roeland, List III, Frederick Alyious, Zhang, Yifei, Christen, David K, Maroni, Victor A., Miller, D. J., & Feldmann, D. M. Characterization of Phase Evolution in YBCO Coated Conductors Produced by the Ex Situ BaF2 Process. United States.
Feenstra, Roeland, List III, Frederick Alyious, Zhang, Yifei, Christen, David K, Maroni, Victor A., Miller, D. J., and Feldmann, D. M. Mon . "Characterization of Phase Evolution in YBCO Coated Conductors Produced by the Ex Situ BaF2 Process". United States. doi:.
@article{osti_931681,
title = {Characterization of Phase Evolution in YBCO Coated Conductors Produced by the Ex Situ BaF2 Process},
author = {Feenstra, Roeland and List III, Frederick Alyious and Zhang, Yifei and Christen, David K and Maroni, Victor A. and Miller, D. J. and Feldmann, D. M.},
abstractNote = {Raman microprobe spectroscopy and scanning electron microscopy were used to study the initial nucleation and growth of YBCO in thick precursors by the BaF2 ex situ process. For quenched films of 2 mum thickness, the data indicate a low density of c-axis nuclei near the substrate, apparently due to a reduced oxygen concentration deep inside the precursor layer. Significant non c-axis growth was also observed; the majority of this material nucleates away from the substrate. Measurement of the conversion rate by in situ XRD for films in the range 0.2-2 {micro}m suggest a weak thickness dependence.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • Raman microprobe spectroscopy and scanning electron microscopy were used to study the initial nucleation and growth of YBCO in thick precursors by the BaF2 ex situ process. For quenched films of 2 mum thickness, the data indicate a low density of c-axis nuclei near the substrate, apparently due to a reduced oxygen concentration deep inside the precursor layer. Significant non c-axis growth was also observed; the majority of this material nucleates away from the substrate. Measurement of the conversion rate by in situ XRD for films in the range 0.2-2 mum suggest a weak thickness dependence.
  • Ex-situ conversion of YBA{sub 2}CU{sub 3}O{sub 7} precursors is an economically attractive process for adding the superconducting layer to a coated conductor substrate. Understanding the phase conversion process and final microstructural assemblage is crucial to maximizing the superconducting properties. Each process used to build a YBA{sub 2}CU{sub 3}O{sub 7} (Y-123) coated conductor creates an interface along which defects or interfacial reactions may result. These defects can be additive and propagate through the entire film structure to affect the growth and properties of the superconducting film. The effects of substrate features, buffer layers, and conversion processes of the ex-situ Y-123 filmsmore » on the resulting microstructures are discussed. Interfacial reactions between the substrate, buffer layers, and Y-123 films are examined. Y-123 films produced from BaF{sub 2}-based precursors deposited by e-beam evaporation or metal organic deposition (MOD) of trifluroacetates are compared in terms of their final microstructures, phase assemblage, and superconducting properties. The initial stages of processing during which phase segregation can occur, Y-123 and secondary phase development, and the degree of conversion completion in fully processed coated conductors are also examined. Implications for thick film (t > 1 {micro}m) development and structural refinements are discussed.« less
  • In situ x-ray diffraction was used to establish the phase relations in high-{Tc} superconductor Ba-Y-Cu-O films grown on SrTiO{sub 3} through the ex situ BaF{sub 2} process. These relations differ from bulk equilibrium phase assemblages in the BaO-Y{sub 2}O{sub 3}-CuO{sub x} system. In particular, BaY2CuO5 (the 'green phase'), a common impurity phase in bulk processing, is absent in the films. Because of the absence of this green phase, the compositional stability field of Ba{sub 2}YCu{sub 3}O{sub 6+x} expands considerably as compared to that of the bulk system, resulting in the tie lines Ba{sub 2}YCu{sub 3}O{sub 6+x}-Y{sub 2}O{sub 3} and Ba{submore » 2}YCu{sub 3}O{sub 6+x}-Y{sub 2}Cu{sub 2}O{sub 5}.« less
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