Electrical properties of medium field, chem-prep varistors. [ZnO doped with Co, Mn, or Al]
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
- Country of Publication:
- United States
- Language:
- English
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420800 -- Engineering-- Electronic Circuits & Devices-- (-1989)
ALLOYS
ALUMINIUM ADDITIONS
ALUMINIUM ALLOYS
CHALCOGENIDES
COBALT ADDITIONS
COBALT ALLOYS
CRYSTAL STRUCTURE
CURRENT DENSITY
DIELECTRIC PROPERTIES
DOPED MATERIALS
ELECTRICAL EQUIPMENT
ELECTRICAL PROPERTIES
EQUIPMENT
GRAIN SIZE
MANGANESE ADDITIONS
MANGANESE ALLOYS
MATERIALS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RESISTORS
SEMICONDUCTOR DEVICES
SEMICONDUCTOR RESISTORS
SIZE
TEMPERATURE EFFECTS
TESTING
ZINC COMPOUNDS
ZINC OXIDES