Density, thermal and FTIR analysis of (50-x)BaO. xFe2O3.50P2O5 glasses

Barium iron phosphate glasses were investigated with DSC analysis and infrared spectroscopy to study the effect of the increasing concentration of Fe 2 O 3 in (50-x)BaO.xF 2 O 3 .50P 2 O 5 glasses and to explain the structure-property relationships in this system. Infrared spectra clearly indicate that with increasing Fe 2 O 3 , the P=O bands tend to disappear showing the opening up of P=O bond and the formation of covalent P-O-Fe linkage. The diminishing of the amplitude of the P-O-P symmetric stretching band and the PO - groups is also observed, which indicate that the P-O-Fe replace both P-O-P and PO - bonds. For 40 mol% Fe 2 O 3 the new bonds at 637 and 593 cm -1 are present in the infrared spectra and are attributed to the Fe-O bond. At this concentration the intensity of P-O-P asymmetric and symmetric stretching vibration decreases significantly simultaneously with the formation of the PO - 3 end groups indicating that the excess iron ions act as a network modifier. So for Fe 2 O 3 addition of less than 30 mol%, the presence of the P-O-Fe bonds enhanced the connectivity of the glasses matrix and leads to the increase of T g , For higher Fe 2 O 3 content the residual iron ions play the role of modifier cations forming the PO - 3 end groups and decreasing the connectivity of the network leading to the decrease of glass transition temperature.