Relationship between nonlinear resistivity and the varistor forming mechanism in ZnO ceramics

Raghu, N and Kutty, TRN (1992) Relationship between nonlinear resistivity and the varistor forming mechanism in ZnO ceramics. In: Applied Physics Letters, 60 (1). pp. 100-102.

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Abstract

The use of a number of perovskite phases M� M�O3-x, as the only forming additive in ZnO ceramics, produces a high nonlinearity index, ?(up to 45), where M� is a multivalent transition?metal ion and M� is an alkaline earth or a rare?earth ion. From this study, the formation parameters crucial to high nonlinearity, such as nonstoichiometry in the as?received ZnO powder, low x values of the additives and fast cooling rate after the sintering, are explainable on the basis of a depletion layer formation at the presintering stage. This is because of the surface states arising out of the chemisorbed oxygen. The depletion layer is retained during sintering as a result of the higher valence state of M� ions, preferentially present at the grain?boundary regions. The fast cooling freezes in the high?temperature concentration of donor?type defects, thereby decreasing the depletion layer width.

Item Type:	Journal Article
Publication:	Applied Physics Letters
Publisher:	American Institute of Physics
Additional Information:	Copyright of this article belongs to American Institute of Physics.
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	30 May 2011 09:31
Last Modified:	30 May 2011 09:31
URI:	http://eprints.iisc.ac.in/id/eprint/37591

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