Structure evolution and tunable luminescence of (Sr0.98−mBamEu0.02)2Ca(Mo1−nWn)O6 phosphor with ultraviolet excitation for white LEDs

Double perovskite (Sr0.98−mBamEu0.02)2Ca(Mo1−nWn)O6 phosphors were successfully synthesized by an improved citrate–EDTA complexing method. The structure evolution and the resulting luminescence variation were systematically investigated by X-ray diffraction with Rietveld structure refinement, Fourier transform infrared spectra, Raman spectra, diffuse reflection spectra and photoluminescence spectra. The increased crystal symmetry and increased lattice parameters were observed from (Sr0.98−mBamEu0.02)2CaMoO6 phosphors. These series of phosphors could be effectively excited by near ultraviolet light and emitted a dominant 594 nm (5D0–7F1). The hypersensitive 5D0–7F2 transition (615 nm) varied with the changed structure symmetry. The CIE chromaticity coordinates were tuned from (0.642, 0.348) to (0.601, 0.389). The luminescence intensity of W6+ substituted powders was greatly enhanced by the blue shift of charge transition band of (Mo/W)O6 with stable emission color. The composition-optimized Sr2Ca(Mo0.5W0.5)O6:Eu phosphor had the highest luminescence intensity and quantum yield comparing to the commercial red phosphors.

Graphical abstractA high efficient phosphor system (Sr0.98−mBamEu0.02)2Ca(Mo1−nWn)O6 for white LEDs with double-perovskite structure was synthesized by EDTA–citric acid complexing method. The bright and tunable red light luminescence was observed by the substitution of Ba2+ and W6+ ions under the ultraviolet excitation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The structure evolution with increased crystal symmetry. ► The tunable luminescence of Eu3+ in double-perovskite powders. ► The efficient shift of charge transition band by the substitution of W6+ for Mo6+. ► Bright red light emission and tunable CIE chromaticity coordinates. ► Double-perovskite powders firstly prepared by an improved citrate–EDTA complexing method.