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Oxidation and Reduction of Bi2Sr1.85Cuo6-Y Crystals

Published online by Cambridge University Press:  28 February 2011

Edward Sonder
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge TN 37830‐6056
B. C. Chakoumakos
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge TN 37830‐6056
B. C. Sales
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge TN 37830‐6056
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Abstract

The effects of oxidizing and reducing atmospheres on the oxygen contents and electrical properties of Bi2Sr1.85CuO6‐y single crystals were investigated. As‐grown crystals were normally semiconducting but became metallic and superconducting after heating the crystals for several hours in oxygen at temperatures between 500 and 800°C Previously superconducting crystals were made semiconducting by heat treatments in helium at temperatures between 700 and 780°C. Changes in the oxygen content of the crystals as well as the oxidation and reduction kinetics during the various heat treatments were monitored using standard thermogravimetric techniques. A good correlation was found between the annealing temperatures in oxygen (helium) at which there was an uptake (loss) of oxygen by the crystals, 500°C (700°C), and the onset (loss) of metallic behavior and superconductivity. From isothermal measurents of the weight change as a function of time, it was found that the apparent activation energies for oxidation and reduction were about 0.5 eV and 2.7 eV, respectively. A partial decomposition of the crystals during the various heat treatments, however, precluded a quantitative analysis of the kinetic data.

Type
Research Article
Copyright
Copyright © Materials Research Society 1990

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References

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