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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The use of a number of perovskite phases Mï¿½ Mï¿½O3-x, as the only forming additive in ZnO ceramics, produces a high nonlinearity index, ?(up to 45), where Mï¿½ is a multivalent transition?metal ion and Mï¿½ 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 Mï¿½ 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|
|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|
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