(50 - x)Na2O-xCuO-10Bi(2)O(3)-40P(2)O(5) glasses (0 less than or equal to x less than or equal to 25) were prepared by melting at 900-1100degreesC mixtures of Na2CO3, Bi2O3, CuO and (NH4)(2)HPO4. DSC measurements give the variation of glass transition temperature T-g from 318 (x = 0) to 378degreesC (x = 25). FFIR spectroscopy shows the evolution of the phosphate skeleton: (PO3)(infinity) chains for 60Na(2)O-40P(2)O(5) 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. (C) 2002 Elsevier Science Ltd. All rights reserved.