Effect of Dysprosium and Samarium RE ion Co-doping on photoluminescence behaviour of novel alkali fluoride bismuth borate glasses: A white LED material

Being inspired from the good spectroscopic traits of alkali fluoride doped borate glasses, a glass series with composition 60B2O3 + 30LiF +10Bi2O3 + (1-x) Dy2O3 + xSm2O3 (where x = 0, 0.2, 0.5, 0.7 and 1 mol%) was prepared by melt quench technique and their Structural, Physical, Optical and Lifetime decay properties were studied and analysed. Prepared samples were X-ray amorphous and their FTIR spectra confirmed that the network is composed of bismuth and borate units. Linear and Non-linear optical properties were studied via UV-Vis-NIR absorption spectra and the variation was found to be influenced by the ratio of RE ions (Dy3+ and Sm3+). Negative values of bonding parameter (delta) were obtained for both the RE ions by nephelauxetic effect and suggested that ionic character of prepared glasses was enhanced by Sm3+ ion co-doping. Emission spectra were recorded for a variety of excitation wavelengths and CIE coordinates, Correlated Colour Temperature (CCT), Colour Rendering Index (CRI) and Colour purity % were calculated. Lifetime decay curves of Dy3+ level 4F9/2 and Sm3+ level 4G5/2 were recorded. CIE coordinates of all compositions, under excitation wavelength 349 nm were displayed in 1931 CIE diagram that indicated improved cool white light emission in Dy3+ and Sm3+ co-doped matrix. The obtained colour parameters inferred that a single matrix is capable of emitting diverse colours with variation of excitation wavelengths and RE ion concentration.