Composition dependence of local structure in lanthanoborate glasses

Abstract

Lanthanoborate glasses ((La 2O 3) x (B 2O 3) 1− x glasses, where x = 0.22, 0.25, 0.28, 0.30) were prepared by rapid-quenching method using twin-roller apparatus. The composition dependence of the local structure in the lanthanoborate glasses was investigated by Raman spectroscopy, XAFS and XPS measurements. The XAFS measurements of La LIII-edge showed that the lanthanum ion is surrounded by nine oxygen atoms and that the La–O distance decreases with increasing of the La 2O 3 content, which shows that the La–O interaction becomes stronger with increasing of the La 2O 3 content. The corresponding result was obtained from XPS spectra for La 3d 3/2 and 3d 5/2. The Raman spectra showed a band at ca. 761 cm −1 which is assigned to metaborate chain structure. It is found that the band decreases with increasing of La 2O 3 content. The bands at 635, 835, and 925 cm −1 increase with increasing of La 2O 3 content, which are assigned to small anionic units, such as metaborate ring, pyroborate, and orthoborate structure, respectively, which shows that the network structure in the glasses changes to small anionic units as the La 2O 3 content increases.