ESR and Mössbauer studies of Bi 2O 3Fe 2O 3 glasses

Abstract

The local structure around iron ions in the Bi 2O 3Fe 2O 3 glasses prepared by the twin-roller quenching method has been examined by means of ESR and Mössbauer measurements. It has been observed that the isomer shift of iron ions increases monotonically with the content of Fe 2O 3. This behavior indicates that as the content of Fe 2O 3 increases, the covalency of FeO decreases. The effective g-value of the ESR spectra of Fe 3+ is slightly larger than 2.00 for all of the glasses. It is considered that this fact is attributable to the effect of the 6p orbital of Bi 3+ and the dipolar interactions between Fe 3+ ions. The distribution function of the electric field gradient around iron ions has been evaluated by fitting the calculated curve into the experimental Mössbauer spectrum. The average value of the electric field gradient estimated from the distribution function increases with increasing the content of Fe 2O 3. Namely, the coordination sphere of O 2− around Fe 3+ is more asymmetric in the glass with higher content of Fe 2O 3. From this result, it is considered that the magnitude of overlap between the 2p orbital of O 2− and the 4s orbital of Fe 3+ decreases with increasing content of Fe 2O 3, which is consistent with the compositional dependence of the isomer shift.