This research investigated the effect of different contents of Tm3+ and different concentration ratios of Yb/Tm on the luminescent properties of BaWO4:Yb3+/Tm3+ nano-crystal synthesized by the hydrothermal method. The results indicated that luminescence intensity reached the strongest when CTm=1.0 mol.% and CYb/CTm =2:1. X-ray diffraction revealed the tetragonal system of BaWO4:Yb3+/Tm 3+ and the grain sizes were between 31 and 45 nm according to Scherrer equation. The results of X-ray diffraction and scanning electron microscopy were similar. Four emission peaks at 454, 475, 647 and 790 nm including two blue emission peaks and two red emission peaks, corresponding to 1D2→3F4 , 1G4→3H6 , 1G4→3F4 and 3H4→3H6 transitions of Tm3+ , were observed under excitation of 980 nm semiconductor laser. Blue emissions at 454 and 475 nm were four-photon and three-photon absorption respectively in accordance with the relationship between luminescence intensity and pump power.
