Raman spectroscopic study of CuO-V2O5-P2O5-CaO glass system

In order to evidence the structural changes induced by CuO and V2O5 in the phosphate glass network and their modifier or former role, x(CuO-V2O5)(100 - x)[P2O5-CaO] glass system was prepared and investigated using Raman spectroscopy (0 <= x <= 40 mol%). Raman spectra of the studied glasses present the specific bands of the phosphate glasses at low concentration of transition metal (TM) ions, but at higher concentration (x > 7 mol%)a strong depolymerization of the phosphate network appears; non-bridging oxygen atoms are involved in V-O-P and Cu-O-P bonds and new short units are formed. For a high concentration of V2O5 (x > 10 mol%) the Raman bands of V2O5 prevail in the spectra; this fact suggests that vanadium oxide imposes its structural units in the network acting thus as a network glass former. 2D correlation analysis was also applied for the concentration-dependent Rarnan spectra in order to verify the assignments of the vibration modes and to find correlations in the changes induced by TM ions content. 2D correlation maps indicate a good correlation between the bands at similar to 705 cm(-1) assigned to P-O-P stretching vibration and at similar to 1175 cm(-1) assigned to PO2 groups which suggest the depolymerization of the phosphate network. The correlation between the 1270 cm(-1) and 930 cm(-1) bands also suggests that V2O5 oxide is responsible for P=O bonds breaking and P-O-V formation, (C) 2008 Elsevier B.V. All rights reserved.