Vibrational Studies of Calcium Magnesium Ultraphosphate Glasses

Phosphate glasses in a system of magnesium calcium phosphate for host matrix luminescent materials wereinvestigated. The glass samples in a series of xMgO–(40- x)CaO–60P2O5 in molar ratio (0x40 mol%) were preparedusing melt-quenching technique. The effect of Mg and Ca content on the structure and glass stability againstcrystallization in the system of MgO–CaO–P2O5 ultraphosphate has been investigated using XRD, Infrared and Ramanspectroscopy. The compositions containing up to 40 mol% of CaO and /or MgO formed glasses and no crystallinephases were detected by XRD. The results of IR and Raman spectroscopy suggest that the phosphate network of theseglasses is composed of middle (Q2) and branching (Q3) phosphate tetrahedral and other calcium/magnesium anions.All the symmetric and asymmetric stretching vibrations of POP and PO2 observed in the spectra are characteristic ofQ3 and Q2 groups. The glass network, especially the Q2 units can be modified by the presence of Ca and Mg ions. Thismodification is primarily associated with the phosphate and the Q2 and Q3 phosphate units randomly distributed in thenetwork. Spectroscopic results shows that the modification of the phosphate network is higher for the Ca containingglasses with respect to the Mg ones, at the same alkali earth content, due to the well defined Ca properties as amodifying cation. Formation of P–O–H bond expresses the hygroscopic nature of the phosphate glasses. This studyshows that the vibrational spectroscopy (Infrared and Raman) are provide useful, complementary information aboutthe network structures of ultraphosphate glasses.