Spectroscopic study on iron doped silica-bismuthate glasses and glass ceramics

Fourier transform infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopic data obtained for iron doped silica-bismuthate glasses were used to investigate the changes induced in the local structure of samples as the ratio between Bi₂O₃ and SiO₂ content changes from 3 to 0.66. The environment of constituent cations was investigated both in vitreous and partially crystallized samples of same composition. Progressive substitution of Bi₂O₃ by SiO₂ contributes to the structural relaxation of vitreous network and enhances glass stability. By crystallization heat treatment the structural units appear to be more uniform as it results from the narrowing of corresponding IR bands and EPR lines. FTIR data show that more affected by composition and heat treatment is the environment of bismuth than that of silicon. EPR data indicate an ordering tendency with SiO₂ content in glasses, while in vitroceramics the iron environment is much uniform in samples with less SiO₂ content, where Bi₁₂SiO₂₀ phase is developed.