Self-propagating high-temperature synthesis of MnZn-ferrites for inductor applications

Abstract

The self-propagating high-temperature synthesis (SHS) route is evaluated for the synthesis of MnZn-ferrite powders that are subsequently processed towards the manufacturing of high initial magnetic permeability polycrystalline specimens for inductor applications. The conditions for the synthesis of particular phases by SHS reactions between iron metal and oxide powders were optimized and the effects of the synthesis parameters on ignition and propagation characteristics were studied. By “fine-tuning” the synthesis parameters, products of a wide spectrum of phases from single-phase, pure and well crystallized (MnxZny)Fe2+δO4 to the oxide of the divalent metals (Mnx′Zny′Fe1−x′−y′)O could be controllably synthesized. Advantages of the synthesis route are demonstrated by tests on properties of merit on final products: combustion powder products were subsequently pressed to torroids, sintered and characterized with respect to their magnetic properties, in comparison to conventionally synthesized samples of the same composition. When sintered under appropriate schedules of oxygen partial pressure profile to avoid phase oxidation at 600°C, SHS powders could be processed to high permeability MnZn-ferrites. At equal average particle sizes SHS powders exhibit higher reactivity and grain growth compared to conventionally synthesized powders. This advantage can be utilized in the manufacturing of high permeability MnZn-ferrites with shorter firing schedules and thus all associated advantages in terms of productivity, production costs or zinc evaporation loss.