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Differential Scanning Calorimetry and Guinier Camera/High-Temperature X-Ray Diffraction Studies of the Oxygen Sublattice Phase Transition in the Yba2Cu3O7−x System

Published online by Cambridge University Press:  28 February 2011

David S. Lee ,
Zezhong Fu ,
Egon Hellstern ,
William L. Johnson ,
Paul Pietrokowsky  and
Konrad Samwer
David S. Lee
Affiliation:
California Institute of Technology, Keck Laboratory of Engineering Materials, Pasadena, CA. 91125
Zezhong Fu
Affiliation:
California Institute of Technology, Keck Laboratory of Engineering Materials, Pasadena, CA. 91125
Egon Hellstern
Affiliation:
California Institute of Technology, Keck Laboratory of Engineering Materials, Pasadena, CA. 91125
William L. Johnson
Affiliation:
California Institute of Technology, Keck Laboratory of Engineering Materials, Pasadena, CA. 91125
Paul Pietrokowsky
Affiliation:
California Institute of Technology, Keck Laboratory of Engineering Materials, Pasadena, CA. 91125
Konrad Samwer
Affiliation:
also I. Physikalisches Institut der Universitat, Göttingen/FRG. California Institute of Technology, Keck Laboratory of Engineering Materials, Pasadena, CA. 91125
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Abstract

We have studied the phase transition of the oxygen sublattice in the YBa2Cu3O7−x system by Differential Scanning Calorimetry (DSC), Guinier Camera, and high temperature x-ray diffraction (ht-xrd) techniques. The transition was examined under different thermodynamic constraints (constant oxygen partial pressure and constant oxygen concentration) and for a range of oxygen partial pressures. The variation of the endothermic peak temperature with DSC scanning rate was used to deduce an activation energy for the transition. The average activation energy for the process is between 38.7–75.0 kcal/mole(l:2:3) [mole], depending on the thermodynamic constraint imposed on the system.

Pressure versus concentration isotherms (P(C)) were used to determine the chemical potential of the oxygen in this system.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 99: Symposium AA – High-Temperature Superconductors , 1987 , 923
Copyright
Copyright © Materials Research Society 1988

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References

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