Glasses xLi 2 O-(50-x)(MoO 3 ) 2 -50P 2 O 5 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 (E opt ) and the Urbach energy (E e ) values have been evaluated by following the available semiempirical theories. The linear variation of (αhν) 1/2 with hν, is taken as evidence of indirect interband transitions. The E opt values were found to decrease with increasing Li 2 O content by causing increase in the number of nonbridging oxygens in network. The Urbach tail analysis gives the width of localized states between 0.48 and 0.74 eV.

The conductivity of glasses in the 50P 2 O 5 À xV 2 O 5 À 50 À x ð ÞLi 2 O system was studied as a function of temperature and composition. For all compositions, the conductivity variation as a function of temperature followed an Arrhenius type relationship. Isothermal variation of conductivity as a function of composition showed a minimum for a molar ratio x near 20. Probable mechanisms for decrease of conductivity with decrease of vanadium oxide concentration were explained. The minimum in room temperature was attributed to increase of V 4+ /V 5+ with decrease of vanadium oxide in specific concentrations of vanadium oxide. Activation energy increased with decrease of V 2 O 5 content. This behavior was attributed to increase of average spacing between vanadium ions.