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

The effect of Bi₂O₃ on the glass transition temperature, electrical conductivity and structure of LiBO₂ 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 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 Bi₂O₃. Bismuth ions have been substituted for boron ions as network former ions.