Chemically homogeneous fine-grained Mn-Zn ferrites by spray drying (abstract)

Abstract

Chemically and structurally uniform Mn-Zn ferrites have been produced using powders synthesized by the spray decomposition of mixed, aqueous Mn, Fe, and Zn nitrate solutions. The particle size of the as-formed powder depended strongly on the metal ion concentration in solution; higher concentrations produced larger sizes. The as-formed particles are spherical, internally hollow, and consisted mostly of Fe2O3. A 900 °C, 6-h argon treatment removed the internal void space and converted the particles mostly to the ferrite spinel phase. Sintering of compacts from heat-treated powders produced microstructures superior to those from as-formed powders. Uniform, fine-grained materials, with a densification level comparable to that of commercial sintered ferrite, have been produced at the very low sintering temperature of 1100 °C. Preliminary work indicates that a higher initial permeability is obtained when a higher sintering temperature was used and the level of its disaccommodation depended on the oxygen partial pressure present during sintering. Both ‘‘accommodation’’ and disaccommodation were observed in the permeability; their magnitudes depended on the peak value of the applied excitation field.