Physical and optical properties of Co2+, Ni2+ doped 20ZnO+xLi2O+(30−x)K2O+50B2O3 (5≤x≤25) glasses: Observation of mixed alkali effect

Abstract Co 2+ and Ni 2+ ions doped 20ZnO + x Li 2 O + (30 − x ) K 2 O + 50B 2 O 3 (5 ≤ x ≤ 25) mol% glasses are prepared using melt quenching technique. Structural changes of the prepared glasses by addition of transition metal oxides, CoO and NiO are investigated by UV–vis–NIR, FT-IR spectroscopy and XRD. The XRD pattern indicates the amorphous nature of prepared glasses. FT-IR measurements of the all glasses revealed that the network structure of the glasses are mainly based on BO 3 and BO 4 units placed in different structural groups in which the BO 3 units being dominant. The optical absorption spectra suggest the site symmetry of Co 2+ and Ni 2+ ions in the glasses are near octahedral. Crystal field and inter-electronic repulsion parameters are also evaluated. The optical band gap and Urbach energies exhibited the mixed alkali effect. Various physical parameters such as density, refractive index, optical dielectric constant, polaron radius, electronic polarizability and inter-ionic distance are also determined.