An interesting method of the processing of hard ferrites comprises amorphisation of the starting
material by rapid solidification followed by subsequent devitrification of the glassy precursor.
The B2O3 was used as a vitrification agent. Chemical composition of the alloys
from the BaO-Fe2O3-B2O3 system has a decisive effect
on the phase constitution and magnetic properties of the final product.
In this study, the influence of the amount of the BaO in the XBaO6Fe2O3B2O3 (X=1-5) system on the phase constitution and properties of the magnets was studied. After rapid solidification the material comprised both amorphous and crystalline phases. Up to BaO content X=2 precipitation of Fe3O4 was observed; for the higher contents phases containing Ba appeared. After devitrification at 950 úC for 1h, for BaO content X=3, only the phase close to the hexagonal barium ferrite Ba0.91Fe11.68O18.2 was obtained. For lower and higher BaO concentrations, Fe2O3 and spinel BaFe2O4, respectively were observed. The best coercivity was obtained for the 2BaO6Fe2O3B2O3, whereas the remanence attained maximum for the BaO in the range from X=2 to X=3.
full paper (pdf, 98 Kb)