J. Phys. IV France 07 (1997) C1-81-C1-82
Influence of B2O3 on the Production of Pure, Gel-Processed Mn-Zn FerritesF. Fan and F.R. Sale
Manchester Materials Science Centre, University of Manchester and UMIST, Grosvenor Street, Manchester M1 7HS, U.K.
The influence of B2O3 on the microstructure and magnetic properties of pure Mn-Zn ferrites has been investigated. A citrate gel processing route was employed to produce highly homogeneous Mn-Zn (Mn0,57Zn0,35Fe2,08O4) ferrites undoped or doped with B2O3 (0-2.5wt%). The results show that B2O3 doping does not benefit the magnetic properties of these ferrites, but promoted grain growth significantly. The initial permeability (µi) of undoped samples has been determined to be about 2400. It sharply drops at 0.1-0.15wt% B2O3 doping levels to 1200-800, and rises back to a maximum value (~2600) at 0.25wt% doping level. Further increases in B2O3 doping level give further decreases in initial permeability. The power loss (PL) is increased with B2O3, content, although a second minimum value of PL is found at 0.25wt% doping level. The changes in magnetic properties are closely related to the observed microstructure. A uniform microstructure of 9.6±0.7µm. pore-free grains is observed in undoped ferrites, whereas at 0.1-0.15wt% B2O3 doping levels discontinuous grain growth is observed. A uniform microstructure with a grain size (39.5±3.3µm) is obtained at the 0.25wt% doping level, beyond which the average grain size decreases with further increases in B2O3 and a general increase in porosity occurs.
© EDP Sciences 1997