The Effect of Electron Irradiation on the Structure of Sodium Aluminum-Iron Phosphate Glasses

Abstract

Glasses of the series (mol.%) 40 Na₂O, (20-x) Al₂O₃, x Fe₂O₃, 40 P₂O₅ were irradiated with 8 MeV electrons to doses equivalent of 0.1, 0.5, and 1.0 MGy and characterized by FTIR spectroscopy and ESR at room temperature. FTIR spectra of all the glasses consist of strong bands due to O-P-O stretching modes in (PO₄)^3- and (P₂O₇)^4- units at 1000-1200 cm^-1, P-O-P stretching modes at 900-950 cm^-1 (v_s) and 700-750 cm^-1 (v_s), and bending modes in the PO₄ units. The wavenumber range lower 800 cm^-1 has some contribution due to stretching modes in MO₄ and MO₆ (M = Al, Fe) units. Moreover the bands at 3300-3700 cm^-1 and 1550-1650 cm^-1 due to stretching and bending modes in both absorbed and structurally bound H₂O molecules were present. As irradiation dose increases the bands due to stretching and bending modes in water molecules and M-O-H bonds become stronger and are split. No essential changes with increasing dose were observed within the spectral range of stretching modes of the O-P-O and P-O-P bonds. Irradiation yields phosphorus-oxygen hole centers - PO₄^2- (D₅) and PO₄^2- (D₆), and PO₃^2- ion-radicals (D₂) observable in ESR spectra of low-Fe glasses. At x>5 their responses are overlapped with strong broad line due to Fe(III). On the whole, with the increase in iron content the glass structural evolution decrease.