Structural and luminescence properties of Dy3+ doped bismuth phosphate glasses for greenish yellow light applications

Different compositions of (5, 10, 15 and 20 mol%) of bismuth and different concentrations (0.5, 1.0, 1.5 and 2.0 mol%) of Dy3+ ion doped bismuth phosphate (BiP) glasses were synthesized by melt-quenching technique. The structural characterization was accomplished by XRD, SEM with EDS, FTIR, FT-Raman and P-31 MAS NMR spectroscopy. The optical properties were studied using absorption and photoluminescence spectroscopy. Different structural groups were identified using FTIR and FT-Raman spectra. The depolymerization of metaphosphate chains are described by the decrease of Q(2) tetrahedral sites allowing the formation of pyrophosphate groups (Q(1)) revealed by P-31 MAS NMR spectroscopic investigations. Judd-Ofelt intensity parameters Omega(lambda) (lambda = 2, 4 and 6) were evaluated from absorption spectra. Radiative parameters such as radiative lifetimes (tau(R)), integrated absorption cross-sections (Sigma) and branching ratios ((beta(R)) were calculated using Judd-Ofelt intensity parameters. From photoluminescence spectra, experimental branching ratios (beta(exp)) and stimulated emission cross-sections (sigma(p)) were calculated for all the observed emission transitions of prepared glasses. The decay profiles for F-4(9/2) level were recorded and fit exponential for 0.5 mol% and non-exponential for higher concentrations of Dy3+ due to non-radiative energy transfer among excited Dy3+ ions. The CIE chromaticity co-ordinates have been calculated from the luminescence spectra which confirmed greenish yellow light emission. (C) 2017 Elsevier B.V. All rights reserved.