Optimization of precursor fiber formation conditions from the Y-Ba-Cu-citric acid-H2O sol

The formation and dissolution of hydroxides, carbonates and citrate complexes, which depend on the pH of the solutions, are very important for the preparation of homogeneous and stoichiometric high-Tc superconducting YBa2Cu3O7-delta fibres from the Y-Ba-Cu-citric acid-H2O system. Since the solubilit...

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Veröffentlicht in:Materials letters 1992-04, Vol.13 (4-5), p.232-240
Hauptverfasser: JIN-HO CHOY, JONG-SEOK YOO, SEOK-YEOL YOON, TAE-SEOK PARK, DUK-YOUNG JUNG, DEMAZEAU, G
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Sprache:eng
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Zusammenfassung:The formation and dissolution of hydroxides, carbonates and citrate complexes, which depend on the pH of the solutions, are very important for the preparation of homogeneous and stoichiometric high-Tc superconducting YBa2Cu3O7-delta fibres from the Y-Ba-Cu-citric acid-H2O system. Since the solubility of each complex ion is a linear function of pH, the solubility diagram can be obtained by plotting the logarithmic molar concentrations calculated from the values of the equilibrium constants and solubility products for hydroxides, carbonates, and citrates. The optimum pH for preparing homogeneous Y-Ba-Cu-citrate gel fibre is estimated to be 6.0 plus or minus 0.2. The ceramic fibre (diameter: 0.1-2 mm) obtained after heat treatment of the gel was black in colour and the corresponding superconducting transition temperatures, Tc, onset and Tc, offset, were found to be approximately 95 and 86 K, respectively. 14 refs.
ISSN:0167-577X
1873-4979
DOI:10.1016/0167-577X(92)90225-9