Concentration dependent luminescence quenching of Er3+-doped zinc boro-tellurite glass

Understanding the mechanism of luminescence quenching in rare earth doped tellurite glass is an important issue. The Er3+-doped boro-tellurite glasses with compositions 30B2O3+10ZnO+(60−x)TeO2+xEr2O3 (where x=0, 0.5, 1, 1.5 and 2 mol%) were prepared by melt quenching method. Structural and optical properties of the proposed glasses were characterized using XRD, FTIR, density, UV–vis-IR absorption and PL spectroscopy. The amorphous nature of these glasses was confirmed by XRD technique. The IR-spectrum reveals five absorption bands assigned to different B–O and Te–O vibrational groups. UV–vis-IR absorption spectrum exhibits seven absorption bands at 6553, 10,244, 12,547, 15,360, 19,230, 20,661 and 22,522 cm−1 corresponding to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 2H11/2, 4F7/2 and 4F3/2 excited states of Er3+ ion respectively. The optical band gap energy (Eopt) corresponding to the direct and indirect allowed transitions decreased, while the Urbach energy and cut-off wavelengths are increased by the introduction of Er3+ ions. The refractive index, density and phonon cut-off edge of the samples are increased and the molar volume decreased with the further addition of dopants. The Judd–Ofelt parameter (Ω2) decreased from 5.73 to 3.13×10−20 cm2 with the increase of erbium ions concentration from 0.5 to 2 mol%. The PL spectra show green emissions for the transition from 2H11/2 and 4S3/2 excited states to 4I15/2 ground state, which show strong quenching due to the addition of Er3+ ions.