Niobium phosphate glasses with a composition of 15K2O-15Na2O-xNb2O5-(70-x)P2O5(x=20,25,30,35,40)have been prepared using the conventional melt-quenching technique.The influence of the niobium content on the structure and properties of the prepared glasses were investigated by infrared(IR)spectroscopy,and differential thermal analysis(DTA).The dielectric properties were evaluated using impedance spectroscopy.The density was measured using Archimedes method and the chemical stability was estimated by recording the weight loss after the glass particles were boiled in distilled water.The results show that both the density and chemical stability increase with the niobium content.The IR spectra measurements suggest that the increase of Nb2O5 leads to an increasing formation of P-O-Nb and Nb-O-Nb bonds,giving rise to the cross-linked glass network [1].Also the increase of niobium content results in an improvement of the stability against crystallization,and the addition of more than 30%mol of Nb2O5 almost suppresses the crystallization.With increasing the niobium content,the electric and dielectric parameters show a decreasing trend which can be the result of the formation of more strengthened glass structure preventing the free movement of the charge carriers [2].