Abstract
Glasses having the compositions x V2O5. (1-x) TeO2 with x = 0(.)04, 0(.)1, 0(.)18 and 0(.)25 were studied by means of optical absorption (UV-VIS-NIR), infrared, Raman and electron paramagnetic resonance spectroscopies. According to the latter method the [V4+]/([V5+] + [V4+]) ratio steadily decreases with increasing V2O5 concentration from 9(.)0 to 2(.)4%. The UV- VIS spectra reveal a shift in cut-off to higher wavelength indicating structural changes. Infrared and Raman spectra show the occurrence of tellurium in this system as trigonal TeO4 bipyramids, TeO3 trigonal pyramids and TeO3+1 polyhedra. By increasing the V2O5 concentrations, a transformation of TeO4 into TeO3+1 polyhedra and TeO3 units has been observed. A high wavenumber band located around 910 cm(-1) which could be assigned to vibrations of short V-O bonds shows a blue shifted with increasing V2O5 content revealing the presence of both VO4 tetrahedra and VO5 bipyramids.