CHARACTERIZATION OF DEVITRIFICATION OF AN IRON-CONTAINING GLASS BY ELECTRICAL AND MAGNETIC PROPERTIES

An alumino-borosilicate glass with 12 mole percent Fe2O3 was heat treated at temperatures from 650° to 800°C for different times, resulting in partial devitrification, i.e., the precipitation of a crystalline spinel phase. The precipitate was visible in the electron microscope and could be identified by x-ray diffraction as γ-Fe2O3 or Fe3O4. The degree of devitrification was apparent in the electrical resistivity and its activation energy. The magnetic properties also change characteristically with devitrification; while the as-cast glass is paramagnetic, the presence of the first very fine precipitate particles is recognized in superparamagnetic behavior. The aspects of the variation of electrical and magnetic properties are discussed and correlated with the devitrification process. © 1968.