Mössbauer and ESR Studies of Potassium Borophosphate Glasses

Abstract

Abstract A linear decrease in isomer shifts of Fe3+ and Fe2+ was observed with an increase in alkali content of borophosphate glasses. The decrease is attributed to a change in the role of iron from a network modifier to a network former, or a decrease in the interatomic distance between iron and oxygen atoms. A linear decrease in quadrupole splitting and linewidth was also observed with increasing alkali content, and the decrease is attributed to the increased symmetry around iron nucleus. A linear decrease in relative absorption area of Fe2+ in Mössbauer spectra was also observed with increasing alkali content of the glasses. This result is attributed to an increased oxidation atmosphere brought about by alkali oxide into BPO4 units. Gamma-ray irradiation (1×108 R) experiments resulted in no change in these Mössbauer parameters, indicating that the glasses are less sensitive to γ-rays than borate or phosphate glasses. ESR absorption intensity of PO42− observed in γ-ray irradiated, iron-free borophosphate glasses increased linearly with an increase in the alkali content in the lower alkali region, and the increase is attributed to a linear increase in the fraction of non-bridging oxygen in PO4 tetrahedra constituting BPO4 (and PO4) units.