Spinel ferrites for phase shifters for airborne phased-array antennas

Lithium ferrite materials for avionic phased array applications at Ku- and X-band were developed by using conventional methods of ceramic processing and firing. Composition variables of Mn, Ti, and Co substitution were used to adjust the magnetic properties to the intended use. Bismuth oxide additions in the range of 0-0.2 wt. percent were used to alter the sintering and grain growth characteristics. Correlations were made between the resulting microstructures and structure sensitive magnetic properties. The stress sensitivity was determined on dense ceramics for different magnetizations and as a function of Mn and Co content. The Co concentration and not Mn was found to be the determining factor. Where single-crystal data were available, correlation was found between sign and magnitude in stress sensitivity and in the anisotropy constant K sub 1. The correlation of stress dependence and the single crystal magnetostriction coefficients was only weakly apparent. (Modified author abstract)