ESR and Mössbauer Studies of Crystallization Process of Iron Phosphate Glass

Abstract 0.7Fe2O3–0.3P2O5 glass was prepared by using a twin-roller method and the crystallization process of this glass was followed by means of ESR and Mössbauer spectroscopy in order to understand the state and the behavior of iron ions in the glass. The ESR line shape of the quenched 0.7Fe2O3–0.3P2O5 glass was much broader than that of the crystallized glass heat-treated at 710 °C for 5 h. Moreover, the linewidth of Mössbauer spectra decreased monotonously through the crystallization process. These facts indicated that there existed a distribution of ligand fields around iron ions in the glass. The Mössbauer parameters, that is the isomer shift and the quadrupole splitting, of the 0.7Fe2O3–0.3P2O5 glass showed that Fe3+ ions in this glass were laid on distorted octahedral ligand fields. The magnetic interaction working in the 0.7Fe2O3–0.3P2O5 glass at room temperature was dipole–dipole interaction. Besides, the Mössbauer spectrum of the glass exhibited no internal field line at room temperature. Hence, the glass is considered paramagnetic at room temperature. At the first stage of crystallization process, the α-Fe2O3 particles precipitated were sufficiently small and so the specimen was superparamagnetic, as revealed from the ESR and Mössbauer spectra of heat-treated specimens.