Microscopic degradation model for ZnO varistors

Bäther, K.‐H.; Brückner, W.; Moldenhauer, W. C.; Bruckner, Heinrich

doi:10.1002/pssa.2210750216

Cited by 3 publications

(1 citation statement)

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“…How to control or reduce the long-term degradation effect remains one of the major challenges for the investigators. In general, the degradation [1][2][3][4][5][6][7][8] refers to a gradual increase (steady or slow) in leakage current under the electric pulse stress or constant applied voltage. Many early investigators [9][10][11][12] had recommended some remedial steps such as heat-treatment (annealing) in conjunction with the adjustment in the varistor formulation and processing variables to control the degradation process for better stability of the device under applications.…”

Section: Introductionmentioning

confidence: 99%

The Degradation of Epoxy Resin‐Coated ZnO Varistors at Elevated Temperatures and Ambient Humidity Conditions

Alim

et al. 2003

Active and Passive Electronic Components

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The degradation of the epoxy resin-coated commercial ZnO varistors at elevated temperatures and ambient humid conditions has been investigated experimentally. It has been observed that the leakage current of the ZnO varistors increases under the voltage stress at elevated temperatures with ambient humidity content. The change in the leakage current corresponding to a fixed electric field with respect to the initial current is taken as the dimensionless degradation index. This index is monitored at various experimental conditions in conjunction with the curing condition of the epoxy resin powder. The results are carefully evaluated, and it has been found that the diffusion process of the moisture into the ZnO varistors plays a key role in the degradation process provided that these varistors had excellent property to begin with. The ionisation of the moisture at the interface between the ZnO block and the epoxy resin coating leads to the increase of the leakage current. Furthermore, the role of the ambient pressure corresponding to the elevated temperatures is considered as the variable to the degradation process. These data are also monitored and analysed as a function of time.

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