High-voltage-gradient zinc oxide varistors: Fabrication and properties
Abstract
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 arristors 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-(SIGMA)m range, compared to 7 to 13 (SIGMA) m in commercial devices. The fin-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 8000 C. Heat treatment in air at temperatures up to 10000 C fully developed the nonohmic electrical properties.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- March 1983
- Bibcode:
- 1983STIN...8328338L
- Keywords:
-
- Electrical Properties;
- Fabrication;
- High Voltages;
- Varistors;
- Voltage Regulators;
- Zinc Oxides;
- Heat Treatment;
- Hot Pressing;
- Metal Oxide Semiconductors;
- Sol-Gel Processes;
- Underground Transmission Lines;
- Electronics and Electrical Engineering