Visible to ultraviolet up-conversion in a novel rare earth-free up-converting phosphor

A novel up-converting phosphor, NaxAlyFx+3y/CaF2 (0.3<x<0.5, 0<y<0.1) composite, is prepared by a hydrothermal process at 180 oC and an annealing treatment at 500 oC. X-ray diffraction (XRD) pattern indicates that NaxAlyFx+3y/CaF2  is a composite consisting of NaF, Na3AlF6, and CaF2. The up-conversion luminescence properties of this phosphor are investigated by fluorescence spectrometer. Results show that NaxAlyFx+3y/CaF2 exhibits visible-to-ultraviolet up-conversion luminescence properties. The emission peaks at 316 and 336 nm are observed when excited by 610 nm, the luminescence lifetime of the emissions is great than 18 ms, and the internal fluorescence quantum yield is 4.2 %. Additionally, the luminescent mechanism of this phosphor is also mentioned.