Dielectric properties, conductivity, UV–visible and infrared spectroscopy of PbO P2O5 NaF glasses containing WO3

Homogeneous (50P2O5–(30 − x)PbO–20NaF–xWO3 where x = 0.0, 5, 10 and 15 mol%) glasses were synthesized using a melt-quenching method. The short range structures of the phosphate samples were examined by Fourier transform infrared spectroscopy. The infrared spectral studies have pointed out the existence of conventional PO4, WO4 and WO6 structural units in the glass network, the number of WO4 tetrahedra decreases as WO3 concentration increases. The optical transmittance and reflectance spectrum of the glasses have been recorded in the wavelength range of 190–1100 nm. The values of the optical band gap Eop for all types of electronic transitions and refractive index have been determined and discussed. The real and imaginary parts ε1 and ε2 of the dielectric constant have been determined. The type of electronic transitions in the present glass system is indirectly allowed and the high values for the refractive index and dispersion are recorded due to the high polarizability of tungsten ions. The results of refractive indices as determined reveal the homogeneity of samples and were found to depend on the glass composition. The electrical properties of the glasses were investigated by ac conductivity from 0.12 to 100 kHz for temperatures ranging from room temperature to 600 K. The study of dielectric properties suggested increase in the insulating character of the glass system with increase in the content of WO3. The ac conductivity in the high temperature region seems to be connected mainly with the polarons involved in the process of transfer from W4+ to W5+ ions.