Effect of copper oxide on structure and physical properties of lithium lead borate glasses

Copper-doped Lead lithium borate glass samples with the composition of (35-x) Pb3O4-xCuO-65Li(2)-B4O7, where x = 5, 10, 15 or 20 mol%, have been prepared by melt quenching technique. Glass-forming ability, density, electrical conductivity, magnetic susceptibility and structural properties of lead lithium borate glasses have been investigated. IR spectroscopic data show that the copper ions play the role of glass modifier. Addition of CuO influences BO3 <-> BO4 conversion. Density is expressed in terms of the structural modifications that take place in glass matrix. The increase in Tg reflects an increase in bond strength, and samples obtain more rigid glass structure. Electrical conductivity and magnetic susceptibility chi data show a variable behavior with the increase in the copper content in two valance states Cu+ and Cu+2. In addition, optical properties depend on the change of the role of copper ions in the samples' structure. Optical energy band gap E-opt and Urbach energy E-tail are determined. The increase in E-opt and UV cutoff with an increase in CuO content is due to the decrease in non-bridging oxygen concentration. The decrease in E-tail at higher concentrations is attributed to the copper ion accumulation in the interstitial positions and to the formation of orthoborate groups. These samples are suitable for the green light longpass filters.