Blue–green color-tunable emissions in novel transparent Sr2LuF7:Eu/Tb glass-ceramics for WLEDs

To introduce ordered nano-structures inside a transparent amorphous matrix with superior optical and mechanical properties bears scientific and technological importance,yet limited success has been achieved.Here,via simple melting-quenching and subsequent thermal activation,we report the successful preparation of transparent nano-structured glass-ceramics embedded in Sr2Lu F7 nano-crystals(~26 nm),as evidenced by X-ray diffraction,transmission electron microscopy(TEM),and high resolution TEM.The successful incorporation of dopants into formed Sr2Lu F7 nano-crystals with low phonon energy results in highly tunable blue–green photoemission,which depends on excitation wavelength,dopant type,and temperature.We found that Eu3+and Eu2+ions co-exist in this hybrid optical material,accompanied by the broadband blue emission of Eu2+and sharp red emissions of Eu3+.A series of optical characterizations are summoned,including emission/excitation spectrum and decay curve measurement,to reveal the reduction mechanism of Eu3+to Eu2+.Furthermore,near green–white photoemission is achieved via the enrichment of Tb3+/Eu3+into crystallized Sr2Lu F7 nano-crystals.The temperature-dependent visible photoemission reveals thermal activation energy increases with the precipitation of Sr2Lu F7 nano-crystals in a glass matrix,suggesting better thermal stability of glass-ceramics than precursor glasses.These results could not only deepen the understanding of glass-ceramics but also indicate the promising potential of Eu3+/Tb3+-ions-doped Sr2Lu F7 glass-ceramics for UV pumped white light emitting diodes(WLEDs)with good thermal stability.