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

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