Kutty, Narayanan TR and Ezhilvalavan, S (1995) Influence of Alkali Ions in Enhancing the Nonlinearity of ZnO-Bi2O3-Co3O4 Varistor Ceramics. In: Japanese Journal of Applied Physics, 34 (11). pp. 6125-6132.
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Zinc oxide ceramic varistors with simplified compositions of ZnO+Bi2O3+Co3O4+M(2)O (M=K or Na) show nonlinearity coefficients (alpha) of 40-75. The electron paramagnetic resonance spectra and optical reflectance spectra show that there is a direct interdependence between the oxidation state of transition metals and the alkali ions. The X-ray photoelectron spectra indicate that the alkali ions preserve a higher oxidation state of cobalt, Co(III), in the grain boundary regions than in the grain interiors having more Co(II). Admittance spectroscopy shows that, while the nature of traps remains unaltered, the trap density increases with the concentration of alkali ions near the interface. The observed defect states are associated with the grain bulk than with the grain boundary interfaces, as indicated by the isothermal capacitance transient signals
| Item Type: | Journal Article |
|---|---|
| Publication: | Japanese Journal of Applied Physics |
| Publisher: | Institute of Pure and Applied Physics |
| Additional Information: | Copyright of this article belongs to Institute of Pure and Applied Physics. |
| Department/Centre: | Division of Chemical Sciences > Materials Research Centre |
| Date Deposited: | 31 May 2011 06:26 |
| Last Modified: | 31 May 2011 06:26 |
| URI: | http://eprints.iisc.ac.in/id/eprint/38031 |
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