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 VOP and CuOP 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 Raman 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 ∼705 cm−1 assigned to POP stretching vibration and at ∼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 PO bonds breaking and POV formation.