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Ba(OH)(2) Equilibria in the System Ba-O-H-F, With Application to the Formation of Ba(2)YCu(3)O(6.5 + x) From BaF(2)-Precursors

The ex situ process for fabricating Ba(2)YCu(3)O(6.5 +) (x) superconducting tapes from BaF(2)- based precursors involves a hydration/oxidation reaction at ≈730 °C to 750 °C generally written as: [Formula: see text] However, microscopic observations of partially processed films suggest the presence o...

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Autores principales: Cook, L. P., Wong-Ng, W., Feenstra, R.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: [Gaithersburg, MD] : U.S. Dept. of Commerce, National Institute of Standards and Technology 2005
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4847571/
https://www.ncbi.nlm.nih.gov/pubmed/27308108
http://dx.doi.org/10.6028/jres.110.011
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author Cook, L. P.
Wong-Ng, W.
Feenstra, R.
author_facet Cook, L. P.
Wong-Ng, W.
Feenstra, R.
author_sort Cook, L. P.
collection PubMed
description The ex situ process for fabricating Ba(2)YCu(3)O(6.5 +) (x) superconducting tapes from BaF(2)- based precursors involves a hydration/oxidation reaction at ≈730 °C to 750 °C generally written as: [Formula: see text] However, microscopic observations of partially processed films suggest the presence of a transient liquid phase during conversion. Alternatively, the conversion reaction can be rewritten as the sum of several intermediate steps, including the formation of a barium hydroxide liquid: [Formula: see text] To evaluate the possibility of a hydroxide liquid conversion step, thermodynamic calculations on the stability of Ba(OH)(2)(liq) have been completed from 500 °C to 900 °C at 0.1 MPa p(total). Based on currently available data, the calculated phase diagrams suggest that a viable hydroxide reaction path exists in the higher part of this temperature range. The calculations indicate that Ba(OH)(2)(liq) may be stable at log [Formula: see text] (Pa) values from ≈4 to 5, provided log p(HF) (Pa) values can be maintained below 0 to −1. Limited experimental confirmation is provided by results of an experiment on BaF(2)(s) at 815 °C, 0.1 MPa [Formula: see text] , in which essentially all F at the surface was replaced by O. It is therefore possible that processing routes exist for producing Ba(2)YCu(3)O(6.5 +) (x) based on the presence of a Ba(OH)(2) liquid, which might have an effect on conversion rates and texturing in the superconducting film.
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spelling pubmed-48475712016-06-15 Ba(OH)(2) Equilibria in the System Ba-O-H-F, With Application to the Formation of Ba(2)YCu(3)O(6.5 + x) From BaF(2)-Precursors Cook, L. P. Wong-Ng, W. Feenstra, R. J Res Natl Inst Stand Technol Article The ex situ process for fabricating Ba(2)YCu(3)O(6.5 +) (x) superconducting tapes from BaF(2)- based precursors involves a hydration/oxidation reaction at ≈730 °C to 750 °C generally written as: [Formula: see text] However, microscopic observations of partially processed films suggest the presence of a transient liquid phase during conversion. Alternatively, the conversion reaction can be rewritten as the sum of several intermediate steps, including the formation of a barium hydroxide liquid: [Formula: see text] To evaluate the possibility of a hydroxide liquid conversion step, thermodynamic calculations on the stability of Ba(OH)(2)(liq) have been completed from 500 °C to 900 °C at 0.1 MPa p(total). Based on currently available data, the calculated phase diagrams suggest that a viable hydroxide reaction path exists in the higher part of this temperature range. The calculations indicate that Ba(OH)(2)(liq) may be stable at log [Formula: see text] (Pa) values from ≈4 to 5, provided log p(HF) (Pa) values can be maintained below 0 to −1. Limited experimental confirmation is provided by results of an experiment on BaF(2)(s) at 815 °C, 0.1 MPa [Formula: see text] , in which essentially all F at the surface was replaced by O. It is therefore possible that processing routes exist for producing Ba(2)YCu(3)O(6.5 +) (x) based on the presence of a Ba(OH)(2) liquid, which might have an effect on conversion rates and texturing in the superconducting film. [Gaithersburg, MD] : U.S. Dept. of Commerce, National Institute of Standards and Technology 2005 2005-04-01 /pmc/articles/PMC4847571/ /pubmed/27308108 http://dx.doi.org/10.6028/jres.110.011 Text en https://creativecommons.org/publicdomain/zero/1.0/ The Journal of Research of the National Institute of Standards and Technology is a publication of the U.S. Government. The papers are in the public domain and are not subject to copyright in the United States. Articles from J Res may contain photographs or illustrations copyrighted by other commercial organizations or individuals that may not be used without obtaining prior approval from the holder of the copyright.
spellingShingle Article
Cook, L. P.
Wong-Ng, W.
Feenstra, R.
Ba(OH)(2) Equilibria in the System Ba-O-H-F, With Application to the Formation of Ba(2)YCu(3)O(6.5 + x) From BaF(2)-Precursors
title Ba(OH)(2) Equilibria in the System Ba-O-H-F, With Application to the Formation of Ba(2)YCu(3)O(6.5 + x) From BaF(2)-Precursors
title_full Ba(OH)(2) Equilibria in the System Ba-O-H-F, With Application to the Formation of Ba(2)YCu(3)O(6.5 + x) From BaF(2)-Precursors
title_fullStr Ba(OH)(2) Equilibria in the System Ba-O-H-F, With Application to the Formation of Ba(2)YCu(3)O(6.5 + x) From BaF(2)-Precursors
title_full_unstemmed Ba(OH)(2) Equilibria in the System Ba-O-H-F, With Application to the Formation of Ba(2)YCu(3)O(6.5 + x) From BaF(2)-Precursors
title_short Ba(OH)(2) Equilibria in the System Ba-O-H-F, With Application to the Formation of Ba(2)YCu(3)O(6.5 + x) From BaF(2)-Precursors
title_sort ba(oh)(2) equilibria in the system ba-o-h-f, with application to the formation of ba(2)ycu(3)o(6.5 + x) from baf(2)-precursors
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4847571/
https://www.ncbi.nlm.nih.gov/pubmed/27308108
http://dx.doi.org/10.6028/jres.110.011
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