Study of the fluorinated lithium borate glasses

Abstract

In order to understand the role of fluorine incorporation on the structure of fast ion conducting lithium borate glasses, the binary xLi2O · (1-x)B2O3 glasses with x = 0.3, 0.4 and 0.5 have been fluorinated and studied using variety of experimental techniques including X-ray photoelectron spectroscopy (XPS), infrared spectroscopy, complex impedance measurement and X-ray diffractometry (XRD). XPS results have shown that O 1s spectra could be described in terms of bridging (BO) and non-bridging oxygens (NBO). The ratio of these two seems to increase with increase in Li2O content. However, this ratio decreases with the increase of fluorine content. F 1s XPS spectra consist of two peaks showing clearly the existence of two different fluorine environments. It was found that with increase in fluorine content the number of four-coordinated boron atoms increases and the BO3 groups with non-bridging oxygen atoms decreases. These results provide definite evidence for fluorine participation in the boron-oxygen network. These structural modifications are found to affect the glass transition temperature Tg dc conductivity of fluorinated lithium borate glasses decreases with the increase of fluorine content. Results from XPS, conductivity and DSC measurements are correlated. © 1995.