The role of Bi 2O 3 as a network modifier and a network former in xBi2O3 · (1 − x)LiBO 2 glass system

Abstract

The effect of Bi 2O 3 on the glass transition temperature, electrical conductivity and structure of LiBO 2 glass has been investigated. T g vs. composition curve shows three different linear regions, while there is an overall decrease in T g with the increase in Bi 2O 3 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 Bi 2O 3 on LiBO 2 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 Bi 2O 3 content. It has a maximum value at x = 0.003 where the conductivity has also exhibited a maximum value. Further increase of Bi 2O 3 content causes decrease in it. For higher Bi 2O 3 content ( x ∗ > 0.005), O 1s spectra of Bi 2O 3 has been separated out from that of Bi 2O 3. Bismuth ions have been substituted for boron ions as network former ions.