STABLE FERRITES FOR R.F. APPLICATIONS.
Abstract
The ferrite body, being developed for this contract, is a Ni-Zn material which has a Ni/Zn mol ratio equal to 1.5. Silicate meneral additions to this body, particularly bentonite, have improved the temperature stability of magnetic permeability and the stability of magnetic permeability and Q with respect to a.c. drive. In the work described in this report, d.c. field influences were found to be less harmful to magnetic permeability and Q for bentonite containing materials. Bentonite additions were found to be seriously harmful however, to the temperature behavior of Q. The Q drops drastically as the temperature decreases below room temperature. For a 10.25 weight % bentonite addition, the Q can drop 70% from 25 C to -50 C. The reason why this happens has not been determined yet but studies of Curie temperature curves (magnetic permeability versus temperature) and physical structure reveal that a two-phase structure exists in the ferrite. Crystallites of inhomogeneous size are imbedded in a matrix which constitutes the second phase. This matrix appears to be crystalline, but of a high silica content. The crystallites appear to have little or no silica, but seem to contain most of the alumina derived from the bentonite. A study of iron oxide content and firing atmosphere indicates that FeO content is related strongly to the temperature behavior of magnetic permeability. As FeO content increases from 1 to 2 weight %, the TF can go from positive to nagative values; changing by as much as 15 PPM DEGREE C. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 31, 1966
- Accession Number
- AD0486660
Entities
People
- Charles F. O'neill
- R. K. Tenzer