Polycrystalline Ferrite Films for Microwave Applications Deposited by Arc-Plasma

Abstract

The arc-plasma spray deposition has been successfully applied to fabrication of planar ferrite microwave integrated circuits. Powdered commercial sintered microwave ferrites were deposited at rates up to 2 mils/min on 1 sq in. dielectric substrates by arc-plasma spray deposition. Process controls produced densities >99% theoretical and also maintained stoichiometric agreement between deposited films and starting material. Annealing expanded <0.1 II-grains to useful sizes of 1 to 20 IIand controlled cation distribution. Special annealing techniques were necessary for ferrites having volatile products such as Ni-Zn compounds. Magnetic and microwave properties of several deposited Mg-Mn ferrites and CeYIG agreed closely with bulk values. Remanence ratios up to 0.87 were noted. Practical application of arc-plasma deposition required material compatibility studies at high temperature. These considerations often superseded microwave properties as criteria for material section.

Arc plasma fabricated phase shifter elements

“…This powder was produced by milling fully sintered bars into a 320 mesh powder, (-50 micron size). The MgMn composition could be sprayed and anne aled over a wide range of conditions, since it is not as susceptable to compositional variations (1) at Monsanto with the same type powder. The C and S band lithium ferrite powders, were a commercial spray dried precalcined powder.…”

Hexaferrite/Polyester Composite Coatings for Electromagnetic-Wave Absorbers

“…The thermal spray processing of ferrites has been investigated for quite a long time. Most of the early research investigations addressed the deposition of spinel ferrites (e.g., Ni-and Ni, Zn-ferrites) as soft-magnetic layers for electronic applications (Ref [14][15][16][17] or of Li ferrites for the production of phase shifters ( Ref 18,19), and, in most cases, the alteration of the crystalline structure and/or the very small crystalline grain size developed upon the rapid solidification of the molten material required post-process annealing (Ref [14][15][16][17] to restore adequate magnetic characteristics. More recent studies have partly solved this problem for spinel ferrites, which crystallize relatively quickly ( Ref 12,20,21).…”

Dependence of Arc Plasma Dispersion Capability on its Temperature

“…Generated by gas discharge, arc plasmas have been widely used in industry and scientific research, such as cutting, welding, [1] nanophase materials preparation [2] and polycrystalline ferrite films deposition, [3] etc. In order to use arc plasmas much better and more widely, their properties must be investigated more clearly.…”