(50-x/2)Na2O-xCuO-(50-x/2)P2O5 glasses (5 less than or equal to x less than or equal to 33.33) have been synthesized and investigated by Fourier transform infrared (FT-IR) and Raman spectroscopies. FT-IR and Raman spectral investigations reveal the formation of P-O-Cu bonds and show the evolution of the phosphate skeleton: (PO3)(infinity) chains for NaPO3 to P2O74- groups in the richest CuO glass. The formation of P-O-Cu bonds increases the cross-link density in the glass network and therefore increases T. of the glasses. The improvement in chemical durability with increasing CuO addition is attributed to the replacement of P-O-P bonds in the glass by more hydratation resistant P-O-Cu bonds and to the strong cross-linking of the phosphate chains by the copper ions. (C) 2003 Elsevier B.V. All rights reserved.