High-voltage-gradient zinc oxide varistors: fabrication and properties
Zinc oxide varistors have many properties that make them attractive as surge arrestors or voltage limiters in high-voltage power transmission systems. The electrical characteristics are influenced by the ZnO grain size, and reducing the grain size would allow the entire device to be much smaller. The practical advantages of smaller arrestors are particularly important for underground transmission lines. Advanced ceramic processing techniques were used to fabricate ZnO varistors having grain sizes in the 3- to 4-..mu..m range, compared to 7 to 13 ..mu..m in commercial devices. The fine-grained varistors exhibited high breakdown voltage gradients, compared to commercial materials. Processing steps included synthesis of highly active powders by sol-gel techniques and hot pressing in a reducing environment to achieve high density at temperatures below about 800/sup 0/C. Heat treatment in air at temperatures up to 1000/sup 0/C fully developed the nonohmic electrical properties.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 6392405
- Report Number(s):
- ORNL/TM-8484; ON: DE83008137
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
HVAC SYSTEMS
VOLTAGE REGULATORS
SEMICONDUCTOR RESISTORS
ELECTRICAL PROPERTIES
FABRICATION
ZINC OXIDES
BREAKDOWN
OVERVOLTAGE
TRANSIENTS
AC SYSTEMS
CHALCOGENIDES
ELECTRICAL EQUIPMENT
ENERGY SYSTEMS
EQUIPMENT
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POWER SYSTEMS
RESISTORS
SEMICONDUCTOR DEVICES
ZINC COMPOUNDS
200301* - Power Transmission & Distribution- AC Systems
EHV & UHV- (-1989)
360204 - Ceramics
Cermets
& Refractories- Physical Properties