Hostname: page-component-78c5997874-j824f Total loading time: 0 Render date: 2024-11-13T08:10:43.476Z Has data issue: false hasContentIssue false
  • English
  • Français

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
Get access

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

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1Levinson, L.M. and Philipp, H.R. in Ceramic Materials for Electronics; Processing, Properties and Applications, edited by Buchanan, R.C. (Marcel Dekker, New York, 1986), pp. 375–402.Google Scholar
2Levinson, L.M. and Phillipp, H.R., The Physics of metal oxide varistors, J. Appl. Phys. 46, 1332 (1975).CrossRefGoogle Scholar
3Pike, G.E.: Electronic properties of ZnO varistors: A new model, Grain Boundaries in Semiconductors, 1982, pp. 369379.Google Scholar
4Kim, J., Kimura, T. and Yamaguchi, T., Effect of bismuth oxide on the sintering of zinc oxide. J. Am. Ceram. Soc. 72, 1541 (1989).CrossRefGoogle Scholar
5Senda, T. and Bradt, R.C., Grain growth in sintered ZnO and ZnO-Bi2O3 ceramics. J. Am. Ceram. Soc. 73, 106 (1990).CrossRefGoogle Scholar
6Dey, D. and Bradt, R.C., Grain growth of ZnO during Bi2O3 liquid-phase sintering. J. Am. Ceram. Soc. 75, 2529 (1992).CrossRefGoogle Scholar
7Lu, C-H., Chyi, N., Wong, H-W. and Hwang, W-J., Effects of additives and secondary phases on the sintering behavior of zinc oxide-based varistors. Mater. Chem. Phys. 62, 164 (2000).CrossRefGoogle Scholar
8Pillai, S.C., Kelly, J.M., McCormack, D.E., O’Brien, P. and Ramesh, R., The effect of processing conditions on varistors prepared from nanocrystalline ZnO. J. Mater. Chem. 13, 2586 (2003).CrossRefGoogle Scholar
9Einzinger, R., Grain boundary properties in ZnO varistors. Am. Ceram. Soc. Bull. 59, 359 (1981).Google Scholar
10Dosch, R.G., Tuttle, B.A. and Brooks, R.A., Chemical preparation and properties of high-field zinc oxide. J. Mater. Res. 1, 90 (1986).CrossRefGoogle Scholar
11 T.J. Gardner and S.J. Lockwood: Scale-up of a batch-type chemical powder preparation process for high field varistor fabrication, Sandia Report, SAND87-2194, Feb. 1988.Google Scholar
12 K.M. Kimball and D.H. Doughty: Aluminum doping studies on high field ZnO varistors, Sandia Report, SAND86-0713, Aug. 1987.Google Scholar
13Gardner, T.J., Doughty, D.H., Lockwood, S.J., Tuttle, B.A. and Voigt, J.A. The effect of low level dopants on chemically prepared varistor materials, Ceramic Transactions (American Ceramic Society Inc., Westerville, OH, 1989), p. 3.Google Scholar
14Hampton, J.H.D., Savage, S.B. and Drew, R.A.L., Experimental analysis and modeling of slip casting. J. Am. Ceram. Soc. 71, 1040 (1988).CrossRefGoogle Scholar
15Wasche, R., Steinborn, G. and Rabe, T., The microstructure of gelcast alumina. Ceram. Forum Int. 72, 24 (1995).Google Scholar
16 A.J. Fanelli and R.D. Silvers: Process for injection molding ceramic composition employing an agaroid gell-forming material to add green strength to a preform, U.S. Patent No. 4 734 237 (1988).Google Scholar
17Fanelli, A.J., Silvers, R.D., Frei, W.S., Burlew, J.V. and Marsh, G.B., New aqueous injection molding process for ceramic powders. J. Am. Ceram. Soc. 72, 1833 (1989).CrossRefGoogle Scholar
18 J. Cesarano III: Polyelectrolyte stabilization and polysaccharide gelation of aqueous alumina suspensions, Ph.D. Thesis, University of Washington, Seattle, WA (1989).Google Scholar
19Labropoulos, K.C., Rangarajan, S., Niesz, D.E. and Danforth, S.C., Dynamic rheology of agar gel based aqueous binders. J. Am. Ceram. Soc. 84, 1217 (2001).CrossRefGoogle Scholar
20Bell, N.S., III, J. Cesarano, Voigt, J.A., Lockwood, S.J. and Dimos, D.B., Colloidal processing of chemically prepared zinc oxide varistors. Part I: Milling and dispersion of powder. J. Mater. Res. 19,(2004).Google Scholar
21Horn, R.H., Mullegans, H., Jones, D.J., Duscher, G., Cannon, R.M. and Ruhle, M., Dispersion forces and hamaker constants for intergranular films in silicon nitride from spatially resolved-valence electron energy loss spectrum imaging. Acta Mater. 46, 2271 (1998).Google Scholar
22Wang, H.F. and Chiang, Y.M., Thermodynamic stability of intergranular amorphous films in bismuth-doped zinc oxide. J. Am. Ceram Soc. 81, 89 (1998).CrossRefGoogle Scholar