Atmospheric corrosion of boron doped iron phosphate glass studied by Raman spectroscopy

Structural stability studies of boron doped 40:60 iron phosphate glasses under humid storage conditions, using Raman spectroscopy is reported. Raman measurements indicate that increased boron doping in these glasses maintaining oxygen/phosphorous ratio constant serves to strengthen the iron phosphate glass network, while for samples with iron/phosphorous ratio a constant, a systematic weakening of the network was observed with increased boron content. Raman measurements on glasses exposed to ambient laboratory conditions (300 K; RH: 70 -80%) for three years reveal excellent structural stability against atmospheric corrosion. Incidentally the sample with the strongest network - 20 mol% boron doped iron phosphate glass with O/P constant, indicated devitrification of the glass surface on storage. Definitive evidence of attack by atmospheric water vapour on the glass surface leading to the above devitrification has been obtained using Raman spectroscopy. Possible pathways for the enhanced atmospheric corrosion of this glass are discussed that would help mitigate this detrimental degradation of boron doped iron phosphate base glasses.