Structural study of (50 − x)Na2O–xCuO–10Bi2O3–40P2O5 glasses

(50−x)Na2O–xCuO–10Bi2O3–40P2O5 glasses (0≤x≤25) were prepared by melting at 900–1100°C mixtures of Na2CO3, Bi2O3, CuO and (NH4)2HPO4. DSC measurements give the variation of glass transition temperature Tg from 318 (x=0) to 378°C (x=25). FTIR spectroscopy shows the evolution of the phosphate skeleton: (PO3)∞ chains for 60Na2O–40P2O5 to P2O7 groups in the glass containing Bi2O3 or both Bi2O3 and CuO. When bismuth and copper oxides replace Na2O, phosphate chains are depolymerized by the incorporation of Bi2O3 and CuO through POBi and POCu bonds. P2O7 groups are predominant structural units in the richest CuO glass. The variation of Tg also supports these results.