Study on the reducing effect of γ-irradiation on Sm 3+ doped LiAl fluorophosphate glasses through optical, structural and luminescence analysis

Undoped and (0.2, 0.5, 1, 3%) Sm2O3-dopants within host LiAl fluorophosphate glasses of the basic composition mol% (P2O5 70, LiF 20, AlF3 10) were prepared. The glasses were characterized by studying their optical, FT infrared and photoluminescence spectra before and after successive γ-radiation (0.25, 1, 3 Mrad). The strong absorption in the UV wavelength region of the optical spectra has been related to trace iron impurity. The Sm3+ ions reveal their characteristic peaks arranged into two groups from about 330 to 460 nm and from 950 to 1550 nm. The major spectra of Sm3+ ions are assumed to be due to transitions from 6H5/2 level to various excited 2s+1Lj levels. The photoluminescence spectra show four emission lines at 560, 596, 642 and 702 nm and their intensities increase with Sm2O3 content. Gamma irradiation produces limited variations in the optical spectra. Examinations of the excitation and emission spectra of the studied glasses at λem = 600 and λex = 402 nm show results supporting the stability of Sm3+ ions after gamma irradiation. However, the change of the excitation wavelength to λex = 535 nm reveals the appearance of two additional peaks which are related to partial reduction of some Sm3+ ions to Sm2+ ions through suggested photoreduction by capturing librated electrons during the radiation process. FTIR spectra of the studied glasses reveal similar vibrational modes related to Q2 and Q3 phosphate groups due to the high content of P2O5 in the glass composition (70 mol%) together with some suggested mixed fluorophosphate groups (PO3F)2−. Gamma irradiation shows limited variations in the FTIR spectra due to the proposed presence of AlF4 and/or AlF6 groups which conduct stability to the glass network.