Magnetic phases present in a SiO2.Al2O3.Fe2O3.K2O glass

The crystallisation and magnetic phases present in a (mol%) 66SiO 2 .16Al 2 O 3 .11Fe 2 O 3 .7K 2 O glass have been investigated by Mossbauer spectroscopy and x-ray diffraction. The amount of a magnetic like microcrystalline Fe 3 O 4 phase and the magnetic hyperfine splitting observed in the Mossbauer spectra depended upon the rate at which the glass was cooled. The Mossbauer spectra for a quenched frit, which contained a magnetite like magnetic phase homogeneously dispersed in aluminosilicate glassy matrix, exhibited a large magnetic spectral component. When the frit was remelted at 1220 K, to prepare glass fibres, the magnetite content decreased. When the crushed frit was spheroidised in a gas/oxygen flame, no magnetic component was present in the Mossbauer spectra. The disappearance of the microcrystalline magnetic component in the glass beads indicates that the cooling rate has a major influence on the crystallinity of this iron containing aluminosilicate material