The role of Bi2O3 as a network modifier and a network former in xBi2O3 · (1 - x)LiBO2 glass system

Abstract

The effect of Bi2O3 on the glass transition temperature, electrical conductivity and structure of LiBO2 glass has been investigated. Tg vs. composition curve shows three different linear regions, while there is an overall decrease in Tg with the increase in Bi2O3 content. The slope of these three straight lines is in a decreasing order. These results are interpreted in terms of the increase in the number of non-bridging oxygen atoms, substitution of Bi-O bond in place of B-O bond and change in Li+ ion concentration. The conductivity vs. composition curve exhibits two maxima which are interpreted in terms of the structural modification effect of Bi2O3 on LiBO2 network and mixed-former effect, respectively. Results obtained from the XPS studies of the samples of composition x ≤ 0.005, have shown that the number of non-bridging oxygen atoms from B-O bond increases with the increase in Bi2O3 content. It has a maximum value at x = 0.003 where the conductivity has also exhibited a maximum value. Further increase of Bi2O3 content causes decrease in it. For higher Bi2O3 content (x > 0.005), O 1s spectra of Bi2O3 has been separated out from that of B2O3. Bismuth ions have been substituted for boron ions as network former ions.