STUDY OF THE FLUORINATED LITHIUM BORATE GLASSES

In order to understand the role of fluorine incorporation on the struc ture of fast ion conducting lithium berate glasses, the binary xLi(2)O .(1-x)B2O3 glasses with x = 0.3, 0.4 and 0.5 have been fluorinated an d studied using variety of experimental techniques including X-ray pho toelectron spectroscopy (XPS), infrared spectroscopy, complex impedanc e measurement and X-ray diffractometry (XRD). XPS results have shown t hat O Is 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 incre ase of fluorine content. F Is 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-coordi nated boron atoms increases and the BO3 groups with non-bridging oxyge n atoms decreases. These results provide definite evidence for fluorin e participation in the boron-oxygen network. These structural modifica tions are found to affect the glass transition temperature T-g. de con ductivity of fluorinated lithium berate glasses decreases with the inc rease of fluorine content. Results from XPS, conductivity and DSC meas urements are correlated.