White light emission and spectroscopic properties of Dy3+ ions doped bismuth sodiumfluoroborate glasses for photonic applications

摘要

Dy3+ ions doped Bismuth sodium fluoroborate glasses (BiNFBxD) have been prepared following the melt quenching technique and characterized through XRD, FTIR, UV-Vis-NIR absorption, luminescence and decay measurements for developing potential WLEDs and yellow lasers. The local symmetry around the Dy3+ ions in the prepared glasses were investigated through optical basicity, covalent character factor, bonding parameter, Judd-Ofelt parameters and Y/B intensity ratio values. The least squares fitting method have been employed to determine the Judd-Ofelt intensity parameters Omega(lambda) to study the nature of bonding and symmetry orientation of the Dy-ligand field environment and to derive the radiative properties for the various emission transitions of the Dy3+ ions. The higher spectroscopic quality factor Omega(4)/Omega(6) values of the prepared glasses indicate its suitability for the fabrication of laser devices and the values were compared with the reported literature. While exciting the Dy3+ doped title glasses at 452 nm (H-6(15/2) -> I-4(15/2)), the emission bands F-4(9/2) -> H-6(15/2) (blue), F-4(9/2) -> H-6(13/2) (yellow) and F-4(9/2) -> H-6(11/2) (red) were observed at 482 nm, 575 nm and 679 nm, respectively. The radiative properties like stimulated emission cross-section (sigma(E)(P)), transition probability (A), effective wavelength (lambda(eff)), branching ratio (beta(R)) and experimental lifetimes (tau(m)) for all the emission bands of the Dy3+ doped title glasses have been computed. From the luminescence spectra the Y/B ratio values, CIE chromaticity color coordinates and Color Correlated Temperature (CCT) for different concentrations of Dy3+ ions were calculated. The CIE chromaticity co-ordinate values of the present glasses suggest their suitability for the development of visible luminescent photonic devices and white light applications. The decay curves pertaining to the F-4(9/2) level have been measured for the title glasses and the fall in lifetime values with the increase in Dy3+ ions concentration could be attributed to the cross-relaxation takes place among the Dy3+ ions and the non-radiative multiphonon relaxation process takes place through the phonon modes of the glass host. The non-exponential behavior of the decay curves have been analyzed through Inokuti-Hirayama model to identify the nature of the energy transfer process takes place among the Dy3+ ions and the dipole-dipole interaction(s) is responsible for the dominant energy transfer process. (C) 2017 Elsevier B.V. All rights reserved.