Rare Earth Ion Doped Fluoride Nanocrystals Preparation And Luminescent Properties

In this paper, the synthesis process and luminescence behavior of Eu³⁺ doped or Er³⁺/Yb³⁺ co-doped YF₃ and BaY₂F₈ nanoparticles were investigated. The effect of heat treatment temperature and the concentration of rare earth ions on the synthesis process and luminescence behavior was discussed.To synthesis rare earth doped YF3 nanoparticles, the mixture of (YCl₃·nH₂O+LnCl₃·nH₂O) and NH₄F was hydrothermal treated at 180℃ in a Teflon-liner autoclave or heated at higher temperatures (400℃⁶00℃) in a stove. The XRD patterns showed that the rare earth doped orthorhombic YF₃ nanoparticles with no second phase have been prepared. The solid solution Y_1-xEu_xF₃ (x=0⁰.4) nanoparticles have been synthesized. The luminescent intensity of the Eu³⁺-doped YF3 nanoparticles increased remarkably with the increasing doping concentration of Eu³⁺ ions. The luminescence concentration quenching resulted from resonance energy transfer between neighboring Eu³⁺ ions occurred at higher Eu³⁺ concentrations (30 mol%). The upconversion luminescence of Er³⁺/Yb³⁺ codoped YF³ nanoparticles under 980 nm excitation has also been observed. With increase of heated temperature, the size of the Er³⁺/Yb³⁺ codoped YF³ nanoparticles increased gradually and upconversion luminescence intensity increased significantly.The rare earth doped BaY₂F₈ nanoparticles have also been synthesized by using the co-precipitation method and the hydrothermal method. The monoclinic BaY₂F₈ particles can be obtained only when heated it at 800℃ in a stove. If heated under 800 0C, only particles with CaF₂ type can be obtained. The crystal size and the luminescent intensity of the Eu³⁺ doped BaY₂F₈ nanoparticles increased remarkably with the increasing the heated temperature. Meanwhile, the emission intensity ratio of ⁵D₁â†'⁷F₂ and ⁵D₀â†'⁷F₁ transition of the Eu³⁺ doped BaY₂F₈ nanoparticles which were synthesized in ethanol was found to be different from that of the BaY₂F₈ nanoparticles which were synthesized in H₂O. With increase of heated temperature, the size of the Er³⁺/Yb³⁺ codoped BaY₂F₈ nanoparticles increased gradually and upconversion luminescence intensity increased significantly. The strong green upconversionluminescence of the Er3+/Yb3+ codoped monoclinic BaY2Fg nanoparticles under 980 nm excitation has also been observed. While the red upconversion luminescence of Er3+/Yb3+ codoped the nanoparticles with CaF2 type has also been observed under 980 nm excitation.