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The Kinetics of Ordering in Gadolinium Zirconate: an Unusual Oxygen Ion Conductor

Published online by Cambridge University Press:  21 February 2011

Sossina M. Haile  and
Scott Meilicke
Sossina M. Haile
Affiliation:
University of Washington, Dept. of Materials Science and Engineering, Seattle, WA, 98195–2120
Scott Meilicke
Affiliation:
University of Washington, Dept. of Materials Science and Engineering, Seattle, WA, 98195–2120
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Abstract

Gadolinium zirconate, Gd2Zr2O7, undergoes an order-disorder transition at ∼1550°C, transforming from a defect fluorite structure (Fm3m) to a pyrochlore structure (Fd3m). Both cations and anions are ordered in the low-temperature, pyrochlore structure. In order to understand the interplay between anion and cation order parameters and ordering rates, the transformation kinetics of Gd2Zr2O7 have been examined via X-ray diffraction. Gadolinium zirconate is of particular interest because the oxygen ion conductivity of the ordered phase is significantly greatly than that of the disordered phase, in contrast to virtually every other known solid electrolyte. This difference in conductivity has provided a second technique for characterizing the transformation kinetics: in situ A.C. impedance spectroscopy. Results of the X-ray diffraction showed the growth of superstructure peak intensity to follow an apparent (time)½ dependence, rather than that expected from a nucleation and growth model. The impedance spectroscopy measurements, on the other hand, showed the conductivity to increase linearly with time. These results suggest the transition is second order in nature.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 398: Symposium C – Thermodynamics and Kinetics of Phase Transformations , 1995 , 599
Copyright
Copyright © Materials Research Society 1998

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References

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