Thermodynamic behavior of high- Tc oxide systems via EMF and related measurements
EMF measurements of oxygen fugacities as function of stoichiometry have been made in the YBa{sub 2}Cu{sub 3}O{sub x}, NdBa{sub 2}Cu{sub 3}O{sub x}, and Nd{sub 1.81}Ce{sub 0.19}CuO{sub x} superconducting systems in the temperature range 400--750{degree}C be means of an oxygen titration technique with an yttria stabilized zirconia electrolyte. The object of our current measurements is to investigate the effect of ionic size of Y, Gd and Nd on immiscibility and other structural transitions in the LnBa{sub 2}Cu{sub 3}O{sub x} system. The shape of the 400{degree}C isotherm for NdBa{sub 2}Cu{sub 3}O{sub x} indicates that, if a miscibility gap is present, it exists at lower temperatures and at values of x that are higher than those for the miscibility gap we deduce in the YBa{sub 2}Cu{sub 3}O{sub x} system. The relative locations of the miscibility gap are consistent with the effects of ionic radii on the composition dependence of {Tc} for these systems. Our results explain the two plateaus in measured values of {Tc} as a function of composition for the YBa{sub 2}Cu{sub 3}O{sub x} system and appear to be consistent with the less pronounced {Tc} plateau found for the NdBa{sub 2}Cu{sub 3}O{sub x} system at higher values of stoichiometry. For a given oxygen stoichiometry, partial pressures of oxygen above NdBa{sub 2}Cu{sub 3}O{sub x} are higher than for the YBa{sub 2}Cu{sub 3}O{sub x} system. Results of limited measurements on the n-type (electron -doped) superconducting Nd{sub 1.81}Ce{sub 0.19}CuO{sub x} system will be presented. 12 refs., 3 figs.
- Research Organization:
- Argonne National Lab., IL (USA)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (USA)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 5877066
- Report Number(s):
- ANL/CP-71426; CONF-9105154-1; ON: DE91010589
- Resource Relation:
- Conference: 2. international conference on rare earth development and applications, Beijing (China), May 1991
- Country of Publication:
- United States
- Language:
- English
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Thermodynamic and nonstoichiometric behavior of promising Hi-Tc cuprate systems via EMF measurements : a short review.
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Related Subjects
BARIUM OXIDES
THERMODYNAMIC PROPERTIES
CUPRATES
RARE EARTH COMPOUNDS
ELECTROMOTIVE FORCE
HIGH-TC SUPERCONDUCTORS
OXYGEN POTENTIAL
PARTIAL PRESSURE
PHASE DIAGRAMS
STOICHIOMETRY
TEMPERATURE DEPENDENCE
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
DIAGRAMS
ENERGY
FREE ENTHALPY
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties