Effect of Li2O on the Refractive Index and Optical Band Gap of Cadmium Phosphate Glasses

Abstract

A series of lithium cadmium phosphate glasses having composition (mol %) x Li 2 O-(50 - x )CdO- 50P 2 O 5 were prepared in a platinum crucible by the melt quenching technique. The quantity x varies in the range 0-40. The mass density and refractive index of these glasses were found in the ranges 3.95-2.89 g/cm 3 and 1.55-1.40, respectively. The optical absorbance studies were also carried out on these glasses to measure their energy gaps. The absorption spectra of these glasses were recorded in the UV-visible range. No sharp edges were found in the optical spectra, which verifies the amorphous nature of these glasses. The optical band gap energies for these glasses were found to be in the range 2.58-3.5 eV. It was observed that the density, the refractive index, and the optical band gap energy decrease with increasing amount of lithium oxide. The band tailing, worked out from the Urbach plots, shows an increase with increasing Li 2 O content and lies in the range 0.47-0.78 eV. The absorption coefficient is observed to show an exponential dependence on the photon energy.