Electrical properties of medium field, chem-prep varistors. [ZnO doped with Co, Mn, or Al]

Technical Report · Fri Jan 01 00:00:00 EST 1988

OSTI ID:5420974

Tuttle, B A; Voigt, J A; Binasiewicz, E J; Kimball, K M

Medium field, chem-prep, ZnO varistors were synthesized and electrically tested. Eight formulations were used with three dopants: (1) Co (0, 0.25, 0.5 mol %), (2) Mn (0, 0.25, 0.5 mol %) and (3) Al (0, 125, and 150 ppM by weight). Al doping produced two dramatic effects: (1) an increase in the electric switching field by factors of 5 to 10, and (2) a significant enhancement of the high current density nonlinearity coefficient. Firing temperatures of 800, 900 and 1000/sup 0/C were used to densify materials and produce varistors with electrical switching fields in the 3 to 10 kV/cm range. Current density vs electric field measurements were made from 1 ..mu..A/cm/sup 2/ to 10 A/cm/sup 2/ using dc and pulse techniques. The varistor with the largest nonlinearity coefficient over this extended current density range was fired at 1000/sup 0/C and contained 0.25 Co, 0.25 Mn, 0.56 Bi (mol %) and 150 ppM Al (by weight). The nonlinearity coefficient was 14 at low current densities (0.1 mA/cm/sup 2/ to 5 mA/cm/sup 2/) and 28 for high current densities (0.1 to 10 A/cm/sup 2/). Because of the large nonlinearity coefficient, this varistor is the best candidate for Sandia applications of all varistors we synthesized. Further, the varistor had an electrical switch field of 5 kV/cm at 10 A/cm/sup 2/ and was greater than 96% of theoretical density. Low field dielectric properties and J vs. E characteristics as a function of temperature were measured for this varistor. 7 tabs.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5420974
• Report Number(s): SAND-87-1824; ON: DE88006147
• Resource Relation: Other Information: Portions of this document are illegible in microfiche products. Original copy available until stock is exhausted
• Country of Publication: United States
• Language: English

Related Subjects

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42 ENGINEERING
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ALUMINIUM ADDITIONS
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CURRENT DENSITY
DIELECTRIC PROPERTIES
DOPED MATERIALS
GRAIN SIZE
MANGANESE ADDITIONS
TEMPERATURE EFFECTS
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