Compositional dependence of red luminescence from Eu3+ ions doped single and mixed alkali fluoro tungsten tellurite glasses

Trivalent europium ions doped single and mixed alkali fluoro tungsten tellurite glasses have been prepared via melt quenching method and characterized by using Raman, optical absorption, excitation, emission and time resolved spectral measurements to understand their utility in visible red emission. Raman spectrum is used to identify different functional groups present in the as prepared glasses. The optical absorption spectra recorded for all the glasses show six bands corresponding to the transitions F-7(0) -> D-6(2), F-7(0) -> D-6(1), E-7(1) -> D-6(1), F-7(0) (-)-> D-6(0), F-7(0) -> F-7(6), and F-7(1) -> F-7(6). An excitation spectrum is used to measure the electron -phonon coupling strength 'g' and phonon energy of the glass host 'h omega'. The photoluminescence (PL) spectra measured under 464 nm excitation show eight luminescence peaks related to the transitions D-5(1) -> F-7(0) (509 nm), D-5(1) -> F-7(1) (537 nm), D-5(1) -> F-7(2) (556 nm), D-5(0) -> F-7(0) (580 nm), D-5(0) -> F-7(1) (592 nm), D-5(0) -> F-7(2) (614 nm), D-5(0) -> F-7(3) (652 nm) and D-5(0) -> F-7(4) (701 nm) in all the glasses under investigation. Utilizing the Judd-Ofelt (J-O) parameters evaluated from the PL spectra, various radiative properties have been evaluated. From the decay spectra, experimental lifetimes were measured which are in turn used to evaluate the quantum efficiencies and non-radiatve decay rates in the as prepared glasses. The branching ratios, stimulated emission cross-section, quantum efficiency, colour coordinates and confocal images captured to confirm the suitability of these glasses for visible red luminescent devices. (C) 2017 Elsevier B.V. All rights reserved.