Chemical states of iron and electrical conduction in FeF 3-MnF 2-PbF 2 glasses

Abstract

The chemical states of Fe ions, the electrical conductivities and the species and transport numbers of charge carriers in FeF3~MnF2-PbF2 glasses were examined by the Mossbauer, conductivity and emf measurements. The FeF3, MnF2 and PbF2 contents of the examined glasses are in the ranges of 21.25 to 80.00, 4.30 to 33.30 and 15.70 to 57.50 mol%, respectively. The Fe ions are present as Fe2+ and Fe3+ in the high spin states and with octahedral F coordination. The Fe2+/(Fe2+ + Fe3+) ratios are in the range of about 9 to 24%, increasing with the FeF3 content. The electrical conductivities increase with the PbF2 content. The highest conductivity is observed in the 21.25 FeF3.21.25MnF2.57.5PbF2 glass, the conductivity at 200°C being 2.4 × 10−4S.cm−1. The charge carriers are both fluoride-ions and electrons. The transport numbers of electrons increase with the FeF3 content, the values at 150°-C being 0.051 in the 21.25 mol% FeF3 glass and 0.134 in the 50.00 mol% FeF3 glass. The fluoride-ion conduction in some of the FeF3~MnF2-PbF2 glasses was found to be faster than the fastest fluoride-ion conduction observed in ZrF4-based glasses.