Impurity doping: a novel strategy for selective synthesis of YF3 and NaYF4 crystals

The phase conversions from YF3 to alpha-NaYF4, as well as alpha-NaYF4 to beta-NaYF4 crystals, accompanied by morphology manipulation and upconversion (UC) luminescence enhancement have been demonstrated by simply increasing the Zn2+ ion doping concentration. We systematically discussed the influence of Zn2+ ion doping on the crystal phase and morphology of samples. Zn2+ ion occupies the Y3+ ion crystal lattice site leading to positive vacancy and lower energy barrier in the reaction of forming NaYF4. Besides, we also investigated the UC luminescence intensity enhancement of beta-NaYF4: Yb/Er by Zn2+ ion doping. These results are expected to provide a new strategy for simultaneous phase control and remarkable UC luminescence enhancement of yttrium fluorides, which may be applicable for other fluorides.