Relative thermodynamic stabilities of constituent oxides of highT c superconductors |
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Authors: | SK Sundaram |
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Affiliation: | (1) Tata Research Development and Design Centre, 1, Mangaldas Road, 411 001 Pune, India;(2) Present address: New York State College of Ceramics, Alfred University, 14802 Alfred, New York, USA |
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Abstract: | A thermodynamic scale of the relative stabilities of constituent oxides can help the choice of stoichiometric multi-component compositions and can provide guidance for judicious selection of heat-treatment conditions for high-T c superconductors. A thermodynamic analysis was undertaken to study Y2O3-BaO-CuO, BaO-K2O-Bi2O3 and La2O3-SrO-NiO systems. The relative stability of the oxides was expressed in terms of two ratios,S v andS p computed using free-energy of formation and vapour pressure data. CuO, Bi2O3 and NiO were taken as reference oxides for YBa2Cu3O7t-gd, Ba0·6K0·4BiO3 and La1·9Sr0·1NiO4 respectively. Thermodynamically, the reference oxide was found to be the least stable amongst the constituent oxides in each of these systems. |
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Keywords: | Gibb’ s free-energy of formation vapour pressure equilibrium oxygen pressure thermodynamic stability |
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