Fluoride Source-Induced Tuning of Morphology and Optical Properties of YF3:Eu3+, Bi3+ and Its Application for Luminescent Inks

A variety of nano/microstructured YF3:0.125Eu(3+), 0.5%Bi3+ samples with specific morphologies was successfully synthesized by a hydrothermal method using various fluoride sources as microstructure-directing agents, and the grain morphology and fluorescence were effectively tailored. The YF3:0.125Eu(3+), 0.5%Bi3+ samples using NH4F, NH4HF2, LiF, NaF, KF, MgF2 CaF2, and BaF2 as fluoride source are abbreviated as S1-S8, respectively. Except for the sample S8, all the diffraction peaks of the other materials (S1-S7) can be indexed to pure YF3 with orthorhombic symmetry. Granule-like nanoparticles, truncated octahedron, octahedron, and bipyramid morphologies were observed in S1-52, S3-S4, S5-S7, and S8 samples, respectively. The grain size of the materials is positively correlated with the cationic radius in fluoride sources, which gives the values of 64 nm to 4.2 mu m. The schematic diagram showing grain formation process has been proposed on the basis of fluoride source-induced morphological evolution. The morphology dependence of fluorescence reveals that the NaF-controlled sample exhibits the strongest orange-yellow emission, while the emission intensity using NH4F as the fluoride source is the lowest. This work offers us a method to effectively control the shape and size of inorganic photoluminescent materials so as to improve the fluorescence by tuning their morphology using different fluoride sources. Furthermore, it has been demonstrated that these luminescent nanoparticles can be used in luminescent ink.