RESEARCH ON DIELECTRICS FOR MICROWAVE ELECTRON DEVICES.
Abstract
High purity, vacuum sintered polycrystalline aluminum oxide was fabricated. This material is transparent and has a density that is 99.5% of theoretical. Further measurements of the properties of aluminum oxide show its actual high temperature electrical conductivity to be about five orders of magnitude less than previously reported. This discrepancy is due to conductivity of ionized gases surrounding the specimen and electron emission of electrodes. Space-charge-limited current studies of sapphire indicate the existence of trapping centers at 2.5 ev below the conduction band, which is probably due to impurity levels. Studies indicate that the properties of aluminum oxide are not sensitive to effects of radiation. Optical absorption studies lead to the conclusion that the bandgap of aluminum oxide is about 8.5 ev. The breakdown strength of polycrystalline aluminum oxide with glassy phase is similar to that of bent single crystal specimens, i.e., less than that of the single crystal material. Electron bombardment of single and polycrystalline materials produces the same type of response, which is relatively independent of the morphology of the dielectric. Internal polarization due to heterogeneous charge distribution can be generated by electron bombardment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1966
- Accession Number
- AD0629942
Entities
People
- C. Peltzer
- D. Peters
- Jennifer Bordeaux
- L. Feinstein
Organizations
- SRI International