Optical spectroscopy assessment of the impact of γ-ray irradiation on Gd³⁺-doped phosphate glass

The effects of γ-ray irradiation (10, 100 kGy) on Gd³⁺-doped phosphate glass were evaluated. Glass irradiated at 100 kGy was characterized alongside the pristine by differential scanning calorimetry, Fourier transform-infrared spectroscopy and Raman scattering, wherein a lack of alteration in thermal and structural properties was supported. Yet, absorption bands developed around 500 nm with γ-ray dose indicating phosphorus oxygen hole center defects. Optical band gap and Urbach energies exhibited decreasing and increasing trends, respectively, reflecting the influence of trapped electrons and increased disorder/defects. By exciting γ-irradiated samples at 265 nm, blue radio-photoluminescence was observed where intensity increased with dose. Decay curves measured monitoring 415 nm emission showed first-order kinetics suggested to arise from phosphorus electron centers. Emission from Gd³⁺ was quenched with gamma-ray dose while the ⁶P_7/2 emitting state lifetimes decreased. Correlations between Gd³⁺ emission intensities and lifetimes with optical band gaps suggest electron center defects perform as ‘energy sinks’.