EPR and Raman investigation of some fluoro-calcium phosphate glasses containing copper ions

The xCuO(1-x)[P2O5?CaF2] glass system with 0 < or = x < or = 40% mol was prepared and investigated by means of EPR and Raman spectroscopy in order to evidence the structural changes induced by the content of copper oxide and its modifier role. EPR analysis indicates a change of the coordination polyhedra of Cu2+ ions from a tetragonal to a tetrahedral local symmetry in the studied glasses. For high content of CuO (x > or = 10 mo l%) the presence of clustered copper ions was evidenced from the spectra. Raman spectra of the studied glasses contain the typical bands attributed to the phosphate glasses. It can be observed that the band at ~980 cm-1 attributed to symmetric stretching vibrations in PO4 and ~1030 cm-1 due to symmetric stretching vibrations in PO3 groups slowly increase in intensity as the phosphate chain breaks and so a larger number of PO3 and PO4 are formed. The band at 1280 cm-1 belonging to the symmetric stretching vibrations in P = O double bonds decrease in intensity with increasing the CuO content and this fact is consistent with the depolymerization of the three dimension phosphate network.