Crystalline phases and amorphous formation regions for the pseudo-ternary BaO-Fe
2O
3-B
2O
3 system were investigated using melt spinning and water quenching techniques. Specimens were heat treated, examined to determine the composition and temperature ranges where the BaO·6Fe
2O
3 precipitated, and the relationship between crystalline phases and magnetic properties was discussed.
All as-quenched specimens produced by melt spinning with a composition range of less than 70 mol%Fe
2O
3 and less than 70 mol%BaO were in an amorphous state, and amorphous formation region in the case of water quenching was restricted to the composition range of less than 40 mol%Fe
2O
3 and more than 20 mol%B
2O
3.
In the pseudo-ternary BaO-Fe
2O
3-B
2O
3 system, the composition regions were classified according to the kind of precipitated phases. In each region, the relationship between the heat treatment temperature and the relative amount of the precipitated phases was clarified. The amount of BaO·6Fe
2O
3 in the composition region between lines P (the tie-line between BaO·6Fe
2O
3 and BaO·B
2O
3) and Q (the tie-line between BaO·6Fe
2O
3-BaO·Fe
2O
3 and BaO·B
2O
3-3BaO·B
2O
3 eutectics) increased as the BaO/Fe
2O
3 ratio in a sample became closer to 1/6. In this region, the composition ranges were determined where fine BaO·6Fe
2O
3 particles of high coercive force (higher than 240 kA/m (3 kOe)) precipitated from the amorphous phases after heating. In the composition region between lines Q and R (the tie-line between BaO·Fe
2O
3 and 3BaO·B
2O
3), some ribbon specimens showed the maximum coercive force of 488 kA/m (6.1 kOe), but they contained very fine BaO·6Fe
2O
3 particles which indicated superparamagnetism.
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