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AC and DC Studies of Non-Exponential Relaxation Processes in Superionic Conductors: Correlation of Conductivity and NMR Studies

Published online by Cambridge University Press:  21 February 2011

C.A. Angell  and
S.W. Martin
C.A. Angell
Affiliation:
Department of ChemistryPurdue UniversityWest Lafayette, IN 47907
S.W. Martin
Affiliation:
Department of Materials Science & EngineeringIowa State University110 Engineering Annex Ames, IA 50011
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Abstract

This paper considers the results of NMR relaxation studies of fast ion glasses in the light of variable frequency electrical conductivity measurements. We show that the low activation energy observed for relaxation processes studied at constant frequency below the temperature of the T1minimum is reproduced by the corresponding constant frequency conductivity measurements. Other characteristics of the constant frequency conductivity in this low activation energy regime, such as the unphysically low pre-exponent, match with the corresponding observations for NMR measurements. Since the activation energy observed at constant frequency in the frequency-dependent regime for conductivity depends on the characteristic departure from exponential relaxation for the conductivity process, we conclude that the NMR activation energy is likewise a simple consequence of the nonexponential character of ionic relaxation in the glass. In this case, the low activation energy attributed to processes probed by NMR relaxation is simply a misinterpretation since it is found, in the wide frequency range studies available to admittance bridge measurements, that all elements of the relaxation spectrum have essentially equal activation energies.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 135: Symposium M – Solid State Ionics I , 1988 , 73
Copyright
Copyright © Materials Research Society 1989

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