Raman and optical spectroscopy study of iron-bearing bio-relevant phosphate glasses: Assessment of γ-ray irradiation effects

Glasses with 50P₂O₅-30CaO-(20 – x)Na₂O-xFe₂O₃ (x = 0.1, 1, 5, 10 mol%) compositions were prepared by melting, and characterized by X-ray diffraction, Raman scattering, and optical spectroscopy. The glasses were subjected to γ-ray irradiation and structural and optical properties evaluated via Raman, absorption, and photoluminescence spectroscopy. The pristine glasses were X-ray amorphous, whereas Raman spectroscopy indicated Fe₂O₃ depolymerizes glass structure. Absorption spectroscopy showed that iron occurred largely as Fe³⁺ with Fe²⁺ revealed at high iron contents. Following γ-ray irradiation, the Raman features were preserved supporting lack of structural alteration. Radiation-induced defects were detected optically for 0.1 mol% Fe₂O₃ but prevented at higher concentrations. Bluish luminescence ascribed to electron centers was detected under 265 nm excitation for 0.1 mol% Fe₂O₃ similar to the irradiated host exhibiting ms-scale decay. The optical properties of γ-irradiated glasses at higher iron contents were like the pristine, supporting an increase in glass network resistance against gamma radiation.