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 μ grains to useful sizes of 1 to 20 μ and 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 These considerations often superseded microwave properties as criteria for material section.