Optical properties of zinc tellurite glasses doped with Cu2Â + ions

Copper-containing ZnO-TeO2 glasses were synthesized using orthotelluric acid, zinc nitrate and the formed batch was doped with copper nitrate. EPR and optical spectra in a wide transparency range from were measured for all glass samples. The values of the spin-Hamiltonian parameters indicate that the Cu2 + ions in the glasses are present in octahedral coordination with some trigonal distortion. The molecular orbital bonding parameters have been calculated and were found to be independent of Cu2 + concentration in glasses. The optical transmittance spectra of doped glasses show a single broad band at 820 nm, which was assigned to the overlapping 2B1g → 2B2g, 2B1g → 2Eg and 2B1g → 2A1g electronic transitions. The spectral dependence of the specific absorption coefficient of Cu2 + ions was calculated for glass samples in the range of 310-2800 nm and was found that the specific absorption coefficient at 820 nm is (103 ± 1) cm− 1/(wt%) and the integral absorption coefficient in the range 0.5-2.8 μm is (63 ± 2) cm− 2/(ppm wt). From the optical data some optical parameters such as the optical energy gap, Urbach energy, metallization criterion and the cut-off wavelength were calculated. It is observed that the optical band gap decreases with an increase in concentration of copper content.