Glasses with composition (60 x)V2O5–40TeO2 x MoO3 with 20 6 x 6 60 (in mol%) have been prepared using the usual melt quenching method. The optical absorption spectra of the glasses have been recorded in the wavelength range 300–800 nm. The position of the absorption edge and therefore the optical band gap values were found to be depend on the glass composition. For these glasses, the optical band gap was found to be in the range 2.03–2.86 eV with increasing of MoO3 concentration. The absorption spectrum fit- ting method was employed to obtain the energy gap. In this method, only the measure- ment of the absorbance spectrum of the glass is needed. For each sample, the width of the band tail was determined. Also, the density and glass transition temperature values indicate that the rigidity and packing of the samples increase with increase in MoO3 con- centration as a network former.
