Optical properties of glasses in the Li2O–MoO3–P2O5 system

Glasses xLi2O–(50-x)(MoO3)2–50P2O5 with x = 10, 20, 30, and 40 mol% were prepared and their optical and electrical properties were investigated. Analysis of the IR spectra revealed that the Li+ ions act as a glass modifier that enter the glass network by breaking up other linkages and creating non-bridging oxygens in the network. The optical absorption edge of the glasses was measured for specimens in the form of thin blown films and the optical absorption spectra of those were recorded in the range 200–800 nm. From the optical absorption edges studies, the optical band gap (Eopt) and the Urbach energy (Ee) values have been evaluated by following the available semi-empirical theories. The linear variation of (αhν)1/2 with hν, is taken as evidence of indirect interband transitions. The Eopt values were found to decrease with increasing Li2O content by causing increase in the number of non-bridging oxygens in network. The Urbach tail analysis gives the width of localized states between 0.48 and 0.74 eV.