Accession Number : ADA019365

Title :   A Review of the Zinc Oxide Varistor.

Descriptive Note : Technical rept.,

Corporate Author : HARRY DIAMOND LABS ADELPHI MD

Personal Author(s) : Campi,Morris

Report Date : SEP 1975

Pagination or Media Count : 32

Abstract : The nonlinear electrical characteristic of zinc oxide varistors is explored in terms of the ceramic sintering process, i. e., sintering temperature, oxide admixture, grain growth, intergranular layer thickness, etc. The property of non-ohmic conduction is traced to the presence of a segregated second-phase accumulation layer, which surrounds the ZnO grains, and acts as an insulating potential barrier. The transition region from ohmic to non-ohmic conduction (prebreakdown region) is explained by the Poole-Frenkel effect in which, for low applied fields, conduction takes place by thermal activation over the field-lowered barrier. In the highly conductive (breakdown) region, conduction corresponds with Fowler-Nordheim field-assisted tunneling. Although Space-Charge-Limited-Conduction (SCLC) theory is considered, it does not appear to be applicable. (Author)

Descriptors :   *VARISTORS, ZINC COMPOUNDS, OXIDES, METAL COMPOUNDS, OXIDES, SURGES, SUPPRESSORS

Subject Categories : Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE