Structural role of TiO2 and Bi2O3 in Na2O-Bi2O3-TiO2-P2O5 glasses

(0.55-y)Na 2 O.yBi 2 O 3 .0.05TiO 2 .0.40P 2 O 5 glasses (0≤y≤0≤25) were prepared and studied. Their physical thermal and spectroscopic properties such as density, molar volume, glass transition temperature and infrared spectroscopy have been investigated in order to understand the structural role of TiO 2 and Bi 2 O 3 in these glasses. In the sodium titanophosphate glass, structures consist of Ti octahedra linked to some pyrophosphate units through Ti-O-P bonds. When bismuth oxide is added to sodium titanophosphate glass, phosphate chains are depolymerised by the incorporation of Bi octahedra through Bi-O-P bonds. Pyrophosphate and orthophosphate units coexist. Pyrophosphate groups are predominant structural units in glasses with the lowest Bi 2 O 3 contents. For richest Bi 2 O 3 glasses, the orthophosphate groups become predominant structural units.