The Dependence of Magnetic and Mechanical Properties on Composition and Processing in Air Fired MnZn Ferrites

摘要

The relationship between mangetic and mechanical properties has been studied as a function of composition, atmosphere and temperature for a series of MnZn ferrites. When processed in air, strength and permeability are critically dependent upon the formation of Mn~(2+) and Fe~(2+) on sintering, and residual stresses introduced via subsequent (re)oxidation upon cooling. In Fe deficient ferrites, properties are determined by the reoxidation of Mn~(2+), which introduces residual tensile tresses on cooling, so that low strength/high u_i are observed. In the Fe excess region, reoxidation of Fe~(2+) on cooling introduces compressive stresses, resulting in high strength/low u_i. Both strength and permeability increase with increasing sintering temperature in Fe excess materials. Cooling in N_2 prevents reoxidation, and results in increased permeability for Fe excess ferrites.