Interface effects in zinc oxide varistors
Abstract
Zinc oxide varistors are electronic ceramic materials whose electrical behavior is dominated by grain boundary interface states. The unique properties of varistor ceramics are determined by the segregation of certain impurity atoms to the grain interface, creating electrical barriers to current flow. At low voltages, electrons transfer over these barriers by thermionic emission. At a critical voltage, electrons transferred over the grain interface have sufficient energy to create minority barriers (holes). These holes act to dramatically decrease the grain boundary electrical barriers leading to the observed rapid increase in current flow. Hole creation has recently been verified by optical means. Measurements of varistor degradation, varistor oxidation-reduction phenomena, and the behavior of primitive varistors with only modest current-voltage nonlinearity indicate that more than one parallel leakage path can control the varistor characteristics at lower currents.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- August 1986
- Bibcode:
- 1986STIN...8717998L
- Keywords:
-
- Electrical Properties;
- Grain Boundaries;
- Interfaces;
- Varistors;
- Zinc Oxides;
- Ceramics;
- Electron Transfer;
- Thermionic Emission;
- Electronics and Electrical Engineering