Some Biassing Effects at the Electrode-Glass Interface
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SOME BIASSING EFFECTS AT THE ELECTRODE-GLASS INTERFACE AKIRA DOI Department of Materials, Nagoya 466, Japan
Nagoya Institute of Technology,
ABSTRACT Informations concerning electrical biassing effects on a Therefore, medium are derived, usually, from the electrodes. we frequently encounter phenomena which are peculiar to the electrode-medium interface(s), besides those due to bulk properties. In this report naive aspect on intrinsic biassing then, as one of effects at the interfaces was presented first; extrinsic origins, the mechanism of silver injection into glass from the silver anode was discussed.
INTRODUCTION Electrical response of a medium is derived, usually, Even informations through the electrode-medium interface. about bulk properties of the medium can be subject to modifiEspecially, in cases cation by the nature of the interface. where some peculiar phase appears near one or both of the interfaces, we would see an overlap of contributions both from The purpose of this work is to the bulk and the interface(s). focus attention on the biassing effects at the electrodeFor convenience sake, we restrict ourselves medium interface. to a single-phase cation-conductive oxide glass, but the results can be extended to any ionic conductors as well. The ac response of a cation conductor, having non-ohmic At low temperaelectrodes, is described as follows (Fig.1). ture the ac response is represented by the parallel RiCi circuit, Ri and Ci corresponding each to the in-phase and 900 out-of-phase component of the current response in the bulk. When the temperature is raised another phase, represented by the parallel R 2C 2, is added in series to the bulk and, by inequalities of C2 >> Ci and R2 >> Ri, the equivalent circuit The R2C2 phase was is approximated by the series RiCz. assigned [1-3] to the positive-ion depleted region (PDR) formed near the anode, as cation conduction proceeds during a halfcycle. In the next halfcycle, on reversing the polarity, disturbances made in the last halfcycle are remedied and a new In short, when non-ohmic electrodes are PDR phase develops. used, an equivalent circuit changes from the parallel RiCi to the series RiC2 with increasing temperatures by the formation of PDR at the bulk-temporary anode interface during each halfOf course, this does not happen to an ohmically cycle. For example, Boukamp and Huggins E43 electroded sample. reported the inability of PDR formation in the Li 3N sample when lithium instead of molibdenum was used as the electrodes. When comparison was made between gold and silver, the gold anode acted as ionically blocking on a glass, that is, the In the anode metal ions are blocked from entering the glass. ac measurements of a blocking-anoded glass at high temperature, we observed a single semicircle in the complex admittance Mat. Res. Soc. Symp. Proc. Vol. 210. 01991 Materials Research Society
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plane which crossed the origin [1,3], due to the series RC 2 circuit as described above. However, in the dc measurements, glass with by biassing the gold-electroded s
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