White light up-conversion in transparent sol–gel derived glass-ceramics containing Yb3+–Er3+–Tm3+ triply-doped YF3 nanocrystals

Transparent glass-ceramics containing YF3 nanocrystals triply-doped with Yb3+–Er3+–Tm3+ ions have been successfully obtained under adequate thermal treatment of precursor sol–gel glasses for the first time to our knowledge. X-ray diffraction and high resolution transmission electron microscopy analysis pointed out the precipitation of YF3 nanocrystals. Up-conversion luminescence features confirm the effective partition of luminescent ions into precipitated nanocrystals. Corresponding energy transfer up-conversion mechanisms and the dependence of the overall emitting colour have been analyzed as a function of doping ions, with varying concentration. In particular, very bright and efficient up-conversion emission, almost matching the standard equal energy white light illumination point of the standard chromaticity diagram, has been achieved showing up as promising candidate material for potential applications in photonic integrated devices and infrared tuneable phosphors.