Hubbell Limited

Lockheed Martin Energy Research Corporation

Mohammad A Alim

Karen C Beal

Robert J Lauf

April D McMillan

Frank A Modine

Gerald D Mahan

Miroslaw Bartkowiak

A varistor includes a Bi-free, essentially homogeneous sintered body of a ceramic composition including, expressed as nominal weight %, 0.2-4.0% oxide of at least one rare earth element, 0.5-4.0% Co.sub.3 O.sub.4, 0.05-0.4% K.sub.2 O, 0.05-0.2% Cr.sub.2 O.sub.3, 0-0.2% CaO, 0.00005-0.01% Al.sub.2 O.sub.3, 0-2% MnO, 0-0.05% MgO, 0-0.5% TiO.sub.3, 0-0.2% SnO.sub.2, 0-0.02% B.sub.2 O.sub.3, balance ZnO.

Rare earth doped zinc oxide varistors

There is disclosed a passivating coating composition suitable for application as a collar to metal oxide varistor valve block cylindrical surfaces comprising a mixture of 64-74 parts by weight of a glass powder, 22-35 parts by weight of water, and 0.5-2 parts by weight of an additive comprising fumed silica, clay and urea.

Method for making metal oxide varistors coated with passivating coating

Passivating coating for metal oxide varistors

It is disclosed that the properties of a ceramic mullite-kaolinite based passivating coating composition applied as a collar to metal oxide varistor valve block cylindrical surfaces are improved by including in the coating composition from 0.03 to 15% by weight of the coating composition one or more of the following additive compounds: TiO.sub.2 ; Y.sub.2 O.sub.3 ; ZrO.sub.2 ; ZnO; Boroflux (2ZNO.sup.. 3B.sub.2 O.sub.3.sup.. 7H.sub.2 O; or 3ZnO.sup.. 2B.sub.2 O.sub.3.sup.. 5H.sub.2 O); or Si.sub.3 N.sub.4. The coating composition comprises by dry weight a mixture of 55-85% mullite and 15-45% kaolinite, one or a mixture of the above additive compounds, and sufficient water to form a sprayable slurry. The inclusion of the additive compound results in enhanced contact adhesion between the collar and the metal oxide varistor peripheral surface.

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Medina, OH, United States of America

Mohammad A Alim