Synthesis and luminescence properties of β-NaYF ₄ doped with Eu ³⁺ and Tb ³⁺

Powdered samples NaYF ₄:Eu ³⁺ and NaYF ₄:Eu ³⁺, Tb ³⁺ are successfully prepared by high temperature solvothermal method. The obtained samples are characterized by X-ray power diffraction(XRD), field emission scanning electron microscopy (FESEM), and photoluminescence(PL) spectra. Experiment results revealed that as-prepared NaYF ₄:Eu ³⁺ and NaYF ₄:Eu ³⁺, Tb ³⁺ crystallized in hexagonal phase without cubic phase, and the size was about 80 nm×100 nm (side length×thickness). When the doping concentration of Eu ³⁺ and Tb ³⁺are various, the lattice structure of samples do not change, indicating that the Eu ³⁺ and Tb ³⁺ ions are completely dissolved in the NaYF ₄ host lattice by substitution for the Y ³⁺. The emission from ⁵D ₀→ ⁷F ₁ (595 nm) and ⁵D ₀→ ⁷F ₂ (618 nm) of Eu ³⁺ ions was observed under excitation of 394 nm light from Xe lamp. The visible light intensity changes with the doping ions of Eu ³⁺ concentration and the influence to crystal structure of Tb ³⁺ ions concentration have been investigated. These results show that the doping ions of Tb ³⁺ change the coordination environment of Eu ³⁺, resulting to stronger red emissions, and electric dipole transition occupied the main contribution.