Mössbauer and ESR studies of non-bridging oxygens in potassium phosphate glasses

Abstract

Mössbauer spectroscopic study was performed to investigate the behavior of non-bridging oxygens in the potassium phosphate glasses denoted by a formula of x K 2O(100− x)P 2O 5 7 Fe 2O 3. The quadrupole splitting values for Fe 2+ and Fe 3+ ions decreased continuously with the alkali content of the glasses in the alkali region of 0–30 mol.%, and increased in the higher alkali region. On the other hand, the Mössbauer absorption area for Fe 2+ increased continuously in the same alkali region ( x = 0–30 mol.%), and then decreased in the higher alkali region. The continuous decrease of the quadrupole splitting, i.e., the increase of the symmetry around the iron and the increase of the absorption area for the Fe 2+ ions are discussed in connection with the increase of non-bridging oxygens at site adjacent to the iron. ESR measurements for the γ-ray irradiated potassium phosphate glasses free from iron were also carried out to confirm the formation of the non-bridging oxygens in the glasses by observing PO 4 2− radicals produced by γ-ray irradiations. We conclude that the ESR absorption intensity for the PO 4 2− radicals linearly increases with the alkali content of the glasses, which was ascribed to the linear increase of non-bridging oxygens in the PO 4 tetrahedra.