Effect of Na2O additions in the crystallization of barium ferrite from a BaO-B2O3-Fe2O3 glass

A glass crystallization method was utilized to synthesize nanosized BaO . 6Fe(2)O(3) platelets from a 0.412BaO-0.258B(2)O(3)-0.330Fe(2)O(3) batch composition. Quenched ribbons were inhomogeneous, showing microclustering and similar to 1 mu m hematite crystals. Na2O substitutions for BaO greatly enhanced the glass-forming tendency of quenched ribbons, though quenched-in similar to 0.5 mu m barium ferrite crystals were infrequently present, The improved homogeneity with Na2O substitution was attributed to lower vapor pressure of BaO during batch melting, which increased its retention in the as-quenched ribbons, Quantities of BaO equal to or in excess of Fe2O3 allowed iron ions to adopt stable network positions in the glass melt. With Na2O substitution, devitrification of dispersed similar to 40 nm barium ferrite particles from phase-separated regions occurred after secondary heat treatment, 5 mol% Na2O batch substitution showed the lowest crystallinity in the as-quenched ribbons, and the highest crystallinity after secondary heat treatment, After optimum devitrification, the maximum values of saturation magnetization and coercivity were 21.22 emu/g and 2.82 kOe, respectively.