Morphology and Luminescent Properties of NaYF 4 Microcrystalline Up-Conversion Phosphors Doped with Ytterbium(III) and Holmium(III) Ions

Microcrystalline phosphors NaY 0.8– x Yb 0.2 Ho x F 4 ( x = 0–0.1) were first synthesized by the hydrothermal method. All synthesized compounds have hexagonal β-NaYF 4 crystalline phase. It has been found that holmium(III) ions isomorphically replace yttrium ions. The maximum intensity of up-conversion emission in the visible region of the spectrum upon 973-nm excitation is observed for the compound NaY 0.78 Yb 0.2 Ho 0.02 F 4 .