Improved white light emission in Dy3+ doped LiF-CaO-Bi2O3-B2O3 glasses

The effect of substituting LiF on physical, structural, thermal, optical and photoluminescence properties of Dy3+ doped calcium bismuth borate glasses is reported in the present work. These glasses have been synthesized in the novel compositional range xLiF-(30-x)CaO-20Bi2O3-50B2O3 + 1 mol% of Dy2O3 (x = 0, 2, 5, 7, 10 and 15 mol%, abbreviated as LFx) through convenient melt-quench route. Non-crystalline nature of each composition has been confirmed through X-ray diffraction. Fundamental vibrations of bismuth-borate groups are identified thorough mid-IR absorption spectra. Thermal properties reveal a non-linear trend in glass transition and crystallization temperatures. In order to evaluate optical band gap, analysis of fundamental absorption edge has been done by considering valid Mott's transitions. The compositional trends in optical band gap have supported thermal and infrared absorption results. Evaluation of photoluminescence emission spectra yielded different emission parameters viz. Y/B ratio, color coordinates (x, y) and CCT (correlated color temperature). It has been found that emission of all compositions lie within the white light region and the emission parameters for samples LF2, LF7 and LF10 lie very close to perfect white light (0.333, 0.333). Therefore, these glasses can play the role of useful materials for WLEDs.