Barium hexaferrite magnet by topotactic reaction method

A new topotactic sintering method using alpha-Fe2O3 (obtained from alpha-FeO.OH) and BaCO3 is developed for preparing cheaper grain oriented barium hexaferrite. Alpha-Fe2O3 and BaCO3 (precipitate grade) are wet mixed in a ball mill in stoichiometric proportion. The mixed slurry is then dried at 110C for about 12 h. The dried powder mixture containing moisture as a binder is uniaxially compacted at (5-10)x 10exp6 kg/m2 pressure. The green compacts are air sintered in the temperature range 1100-1300C for 1 h. The best results of the sintered ferrite show maximum energy product (BH)max in the range 7-10 kT A/m. The bulk of commercial requirements for toy magnets etc. may be met by this method of production which eliminates steps like calcination and cost intensive wet magnetic compaction. 7 refs.