Influence of CuO and Al2O3 addition on the optical properties of sodium zinc phosphate glass absorption filters

The phosphate glasses having chemical composition of 45P2O5-(35-y)ZnO-(20-x)Na2O-xCuO-yAl2O3 (0 ≤ x ≤ 5, 0 ≤ y ≤ 4) have been prepared using the melt quenching technique. XRD analysis has been carried out on the investigated samples in order for confirming the amorphous nature. The density has been measured using Archimedes method and then the molar volume has been calculated. It is found that the density, unlike molar volume, increases with increasing CuO content. This is due to the difference in atomic weight between Cu and Na. Addition of Al2O3 causes a slight decrease in density and a large increase in molar volume. The ionic concentration, inter ionic distance and oxygen packing density have been calculated for all investigated glasses. Using optical absorption, the optical bandgap has been calculated and found to decrease with increasing CuO concentration. This decrease becomes slower in the presence of Al2O3 which makes an increase in the bandgap at the the absence of CuO. The transmission spectrum of the investigated glasses shows that the samples containing CuO behave as bandpass filters. the characterized parameters of these filters, i.e. area, center, width, height and full wave half maximum (FWHM) of bandpass, have been estimated. These parameters have been found to be more affected by CuO and Al2O3 addition. The refractive index, extinction coefficient, real and imaginary part of the dielectric constant have also been calculated at the bandpass.