A range of phospho-tellurite glasses containing gadolinium was prepared and infrared absorption spectra were measured. Structural changes, as recognized by analyzing band shapes of IR spectra, revealed that Gd2O3 causes a higher extent of network polymerization as far as x <= 15 mol% because the conversion of [TeO4] to [TeO3] structural units is supported by the increase of metaphosphate structural groups. While for x between 20 and 30 mol% Gd2O3 show some drastic structural modifications which lead to the increase in the glass fragility. Thus the addition of V2O5 resulted in gradual depolymerization of the phosphate chains and formation of short phosphate units, which are linked to vanadium through P-O-V bonds. The formation of P-O-V bonds increases the cross-link between the phosphate chains and the bending mode of Te-O-Te or O-Te-O linkages.