Thermodynamic stability field of the 123 and 124 phases in the Y[sub 2]O[sub 3]--BaO--Cu--O system
- Department of Geological and Geophysical Sciences and Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544 (United States)
The partial molar entropy of solution of oxygen in YBa[sub 2]Cu[sub 3]O[sub [ital x]],[Delta][ital [bar s]][sub O], has been computed using equilibrium data and the recently measured partial molar enthalpy of oxygen. While [Delta][ital [bar h]][sub 0] is independent of oxygen content (6.0[lt][ital x][lt]7), [Delta][ital [bar s]][sub O] depends on [ital x]. The [ital p][sub O[sub 2]], [ital T] location of phase equilibrium between the 123 and 124 superconducting phases is calculated. The standard free energies of interactions of the superconducting phases with carbon dioxide (CO[sub 2]) and water vapor (H[sub 2]O) have been assessed. The free energies of carbonation of the fully oxidized 123 and 124 phases are [minus]323[plus minus]22 kJ mol[sup [minus]1] and [minus]291[plus minus]32 kJ mol[sup [minus]1], respectively. The free energies of hydration of the 123 and 124 are [minus]397[plus minus]22 kJ mol[sup [minus]1] and [minus]469[plus minus]32 kJ mol[sup [minus]1], respectively. These large exothermic values show that degradation of these superconductors at ambient conditions is thermodynamically favorable.
- DOE Contract Number:
- FG02-89ER45394
- OSTI ID:
- 5774561
- Journal Information:
- Journal of Materials Research; (United States), Journal Name: Journal of Materials Research; (United States) Vol. 8:12; ISSN JMREEE; ISSN 0884-2914
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CALORIMETRY
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CUPRATES
ENERGY
FREE ENERGY
HIGH-TC SUPERCONDUCTORS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
STABILITY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES