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Dielectric resonance of zinc oxide varistor ceramics

Ezhilvalavan, S and Kutty, TRN (1997) Dielectric resonance of zinc oxide varistor ceramics. In: Iete Journal Of Research, 43 (2-3). pp. 233-243.

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Official URL: http://www.iete.org/

Abstract

Polycrystalline ZnO ceramics formulated with higher than normally known concentrations of grain boundary layer modifying additives, show resonance in capacitance around 10 to 30 MHz, which is in a much lower frequency range than so far reported. The observed resonance is due to the total inductance of the varistor ceramics wherein the grain boundaries are shorted at higher frequencies following a distinct relaxational maximum, arising from the dynamic exchange of charge carriers at the grain interiors and the trap states that are formed at the depletion regions around the grain boundaries. Methods of formulation, total content of the additives and processing of ceramics seem to be crucial in attaining capacitance resonance at megahertz frequencies. Capacitance above the breakdown voltages show negative values, indicative of oscillatory charge redistribution involving multivalent states of Co and the shallower interface states. Multiple trapping relaxations are evident from the complex-plane capacitance studies. The admittance spectroscopy data show that the type of trap states changes with the addition of grain boundary layer modifiers accompanied by considerable increase in the density of traps. The capacitance-voltage studies show direct correlation between the magnitude of capacitance resonance and the nonlinearity coefficient in current voltage relations.

Item Type: Journal Article
Additional Information: Copyright of this Article belongs to The Institution of Electronics and Telecommunication Engineers (IETE).
Keywords: Semiconductors;surfaces and interfaces;grain boundaries;dielectric response;localized electronic states.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Depositing User: Mr. S Muthuraja
Date Deposited: 01 Jun 2009 06:18
Last Modified: 01 Jun 2009 06:18
URI: http://eprints.iisc.ac.in/id/eprint/18856

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