Dielectric analysis of tungsten-phosphoniobate 20A2O-30WO3 -10Nb2O5 -40P2O5 (AÂ =Â Li, Na) glass-ceramics

In the present work we present the preparation of 20A2O-30WO3-10Nb2O5-40P2O5 (A = Li, Na) transparent glasses. These glasses were heat-treated in air, at 550 °C and 650 °C for 4 h. The structure of the obtained samples was studied by X-ray powder diffraction (XRD) and Raman spectroscopy and the morphology by scanning electron microscopy (SEM). The dc (σdc), ac (σac) conductivity and dielectric spectroscopy measurements were performed in the function of the temperature and were related with the structural changes of the glass structures.