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Colloidal processing of chemically prepared zinc oxide varistors. Part II: Near-net-shape forming and fired electrical properties

Published online by Cambridge University Press:  03 March 2011

Nelson S. Bell ,
James A. Voigt ,
Bruce A. Tuttle  and
Duane B. Dimos
Nelson S. Bell*
Affiliation:
Sandia National Laboratories Albuquerque, New Mexico 87185
James A. Voigt
Affiliation:
Sandia National Laboratories Albuquerque, New Mexico 87185
Bruce A. Tuttle
Affiliation:
Sandia National Laboratories Albuquerque, New Mexico 87185
Duane B. Dimos
Affiliation:
Sandia National Laboratories Albuquerque, New Mexico 87185
*
a) Address all correspondence to this author. e-mail: nsbell@sandia.gov
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Abstract

Chemically prepared zinc oxide powders were processed for the production of high aspect ratio varistor components (length/diameter >5). Near-net-shape casting methods including slip casting and agarose gelcasting were evaluated for effectiveness in achieving a uniform green microstructure that densifies to near theoretical values during sintering. The structure of the green parts was examined by mercury porisimetry. Agarose gelcasting produced green parts having low solids loading values and did not achieve high fired density. Isopressing the agarose cast parts after drying raised the fired density to greater than 95%, but the parts exhibited catastrophic shorting during electrical testing. Slip casting produced high green density parts, which exhibit high fired density values. The electrical characteristics of slip-cast parts are comparable with dry-pressed powder compacts.

Keywords

Dielectric propertiesCastingDensification
Type
Articles
Information
Journal of Materials Research , Volume 19 , Issue 5 , May 2004 , pp. 1341 - 1347
Copyright
Copyright © Materials Research Society 2004

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