Novel rare earth ions-doped oxyfluoride nano-composite with efficient upconversion white-light emission

Transparent SiO2–Al2O3–NaF–YF3 bulk nano-composites triply doped with Ho3+, Tm3+ and Yb3+ were fabricated by melt-quenching and subsequent heating. X-ray diffraction and transmission electron microscopy measurements demonstrated the homogeneous precipitation of the β-YF3 crystals with mean size of 20 nm among the glass matrix, and rare earth ions were found to partition into these nano-crystals. Under single 976 nm laser excitation, intense red, green and blue upconversion emissions were simultaneously observed owing to the successive energy transfer from Yb3+ to Ho3+ or Tm3+. Various colors of luminescence, including bright perfect white light, can be easily tuned by adjusting the concentrations of the rare earth ions in the material. The overall energy efficiency of the white-light upconversion was estimated to be about 0.2%.