The zinc barium metaphosphate glasses, (50 - x)BaO-xZnO-50P(2)O(5) with 0 less than or equal to x less than or equal to 50 were prepared and studied. An analysis of the infrared spectra, of molar volume and of the variation of glass transition temperature with the ZnO content are discussed in order to describe the structural effect of Zn2+ additions in these glasses. The density of (50 - x)BaO-xZnO-50P2O5 glasses decreases continuously as the ZnO substitution increases, in accordance with the mass differences between BaO and ZnO. For x less than 30 mol%, the glass transition temperature decreases by the decrease in phosphate chain length. For larger x (30 less than or equal to x less than or equal to 50 mol%), the T-g increase, due to the effect of the high field strength of the cations Zn2+ increased due to the increase in the amount of Zn2+ ions in the glasses, that results in a tighter network formed by the shortened phosphate chain length. (C) 2004 Elsevier Ltd. All rights reserved.