Role of molybdenum ions on physical, optical, electrical and vibrational studies in Er super(3+) co-doped TeO sub(2)-ZrO sub(2)-PbCl sub(2) glasses

(75 - x)TeO sub(2)-15PbCl sub(2)-xMoO sub(3)-10ZrO sub(2) doped with 5 mol% Er sub(2)O sub(3), where x = 2.5, 5, 7.5 and 10 mol%, glasses were investigated by Raman spectroscopy, dc conductivity, optical transmittance spectra and density were measured. Mo[inline image]O bonds are present in the entire glass composition. The glasses contain TeO sub(4) trigonal bipyramids, TeO sub(3+1) polyhedra and MoO sub(6) octahedra as basic structural units. Glasses having low MoO sub(3) content contain MoO sub(6) octahedra having two Mo[inline image]O bonds. As MoO sub(3) content increases, the fraction of Mo[inline image]O bonds to Mo super(6+) decreases. The dc conductivity increases with increase in MoO sub(3) content, and the activation energy decreases with increase in MoO sub(3) content. The optical band gap (E sub(opt)) and Urbach energy (E sub(r)) were determined from the optical transmittance spectra of the polished samples recorded in the spectral range from 190 to 1100 nm at room temperature (RT). Variation in these optical parameters has also been associated with the structural changes occurring in these glasses with increase in MoO sub(3) content, and the present glasses behave as indirect gap semiconductors.