Magnetic properties and microstructure of Ba-ferrite powders prepared by ball milling

The magnetic properties and the phase constitution of barium ferrite powders with Fe/Ba ratios varying from 7 to 15 and heat-treated in the temperature range 1000-1200 degreesC are reported. The results showed that heating temperature was effective in increasing the magnetization (M-s) of the powders for ratios greater than or equal to 10. For lower ratios M-s increased initially and then decreased with increasing temperature, presumably due to the formation of BaFe2O4. The coercivity (H-ci) presented a maximum for all the compositions and then decreased due to particle growth. In addition, the effect of the milling time on the magnetic properties and powder characteristics was investigated. It was found that 40 h of milling led to having samples with less volume fraction of second phases and that the magnetic properties were also maximized. TEM micrographs show particle sizes varying from 0.1 to 2 mum. (C) 2001 Elsevier Science B.V. All rights reserved.