Effect of Al2O3 on the phase composition and structural features of iron pyrophosphate glasses

Abstract The effect of Al2O3 substitution for Fe2O3, with concentration deliberately much higher than the solubility limit of the baseline glass, on phase composition and structure features of iron pyrophosphate glasses was investigated by using Fourier transform infrared spectra and Raman spectra. The results show that AlPO4 phase appears in the amorphous structure of iron pyrophosphate glasses when the Al2O3 substitution for Fe2O3 is higher than 10 mol%. The structure of the iron pyrophosphate samples predominantly consists of Q1 phosphate group. Generally, the substitution of Al2O3 induces the decrease of Q1 and Q2 phosphate groups and the increase of Q0 phosphate group. Moreover, the formation of AlPO4 phase enhances the variation rate of Q0 and Q1 groups but reduces the decreasing rate of Q2 group. In addition, the phosphate network is depolymerized but the whole glass network is enhanced by the Al2O3 substitution. The effect of AlPO4 phase in the iron pyrophosphate samples is also discussed. The conclusions provide researchers with the role of Al in phase composition and structure features of iron pyrophosphate glasses as potential matrix for immobilization of specific nuclear waste.