Development of Advanced Microwave Components and Techniques, Planar Hexagonal Ferrites and Devices

摘要

Material parameters and methods of preparation of a series of Y-compounds are reported. The high dielectric loss measured in the planar hexagonal ferrites is a limitation on performance of the material in most microwave devices. While an intense program was conducted to minimize dielectric loss, the lowest dielectric loss measured at X-band frequencies on a variety of Y-compositions with differing iron stoichiometry and preparation techniques was 0.01. The inferior characteristics of the planar materials make them less desirable for use in microwave devices than other ferrite materials. Measurements and analyses of the applications of planar hexagonal ferrites in isolators and differential phase shifters are reported. Both theoretical analysis and experimental results strongly indicate that in most microwave devices no improvement in device performance can be obtained by utilizing planar hexagonal ferrites in preference to other ferrite materials. A study of grain orientation in cubic ferrites is also reported. X-ray diffraction studies of nickel ferrite pressed in the presence of a dc magnetic field have shown positive evidence of crystallite orientation. Narrowest X-band linewidth measured on this partially oriented nickel ferrite is 268 oe.