Preparation and Magnetic Properties of Ba-Ferrite Particles Using the Super-Critical Water Crystallization Method

초록

Barium ferrite particles were synthesized from Ba(NO3)2, Fe(NO3)3 and KOH mixed solutions using hydrothermal crystallization in supercritical water. The experimental apparatus for production of barium ferrite is a flow-type apparatus. Fine barium ferrite particles were produced because supercritical water causes the metal hydroxides to be rapidly dehydrated before significant growth takes place. The effects of Fe/Ba ratio and reaction time on the formation, particle size, and magnetic properties of barium ferrite were studied. When Fe/Ba ratio were varied from 0.5 to 1.2, single-phase barium ferrite powder was only produced in the range of 0.5<Fe/Ba<2. Also, with elevating reaction time, the BaO.6Fe2O3 particle size grew samaller. Especially, uniform barium hexaferrite particles of size 100-200nm were obtained of 80sex. In this study, therefore, single-phase barium ferrite particles are highly stable and can be produced continuously in a reation time of less then 2 min.