Synthesis, Multicolor Luminescence And Energy Transfer Of Lanthanide Ions Doped Fluoride Luminescent Materials

Rare earth fluorides have wide application prospects in the fields of full gamut display,LED lighting,photoelectric conversion,biomedicine and so on due to their excellent properties,such as low phonon energy,high luminescence efficiency,long lifetime and good biocompatibility.In this thesis,NaGdF₄,BaGdF₅ and NaBiF₄ are used as matrix materials,which doped with different rare earth ions(Yb³⁺,Er³⁺,Eu³⁺,Dy³⁺,Tb³⁺,Sm³⁺)to achieve multicolor tunable luminescence.The crystal synthesis,energy transfer and magnetic properties are discussed.The main contents are as follows:1.?-NaGdF₄:Yb³⁺/Er³⁺/Eu³⁺phosphor was synthesized by L-arginine-assisted hydrothermal method.The obtained NaGdF₄ crystal shows rod-like morphology.Under different wavelengths excitation,the sample has up-and down-conversion dual-mode luminescence characteristics.Under the excitation of 274 nm ultraviolet light,the luminescent color of the sample changes from yellow-green to orange.Under the excitation of 377 nm,the samples emit yellow light with different tones.Excited by 980 nm infrared light,NaGdF₄:Yb³⁺,Er³⁺,Eu³⁺samples emit yellow-green light.The energy transfer processes from Gd³⁺to Er³⁺,Gd³⁺to Eu³⁺and Er³⁺to Eu³⁺in NaGdF₄:Yb³⁺/Er³⁺/Eu³⁺phosphors were observed.The samples prepared at room temperature have paramagnetic properties.2.BaGdF₅:Dy³⁺,Eu³⁺nano-phosphors were synthesized by a simple one-step hydrothermal method.Under 275 nm ultraviolet excitation,BaGdF₅:Dy³⁺phosphors exhibit blue light emission,BaGdF₅:Eu³⁺phosphors exhibit orange red-light emission and BaGdF₅:Dy³⁺and Eu³⁺phosphors exhibit white light emission.The energy transfer mechanism between Dy³⁺and Eu³⁺is dipole-dipole interaction.The prepared samples exhibit paramagnetic properties at room temperature.3.NaBiF₄:Tb³⁺,Sm³⁺phosphors were rapidly synthesized by precipitation method at room temperature.The synthesized phosphors are hexagonal NaBiF4 crystals,and the higher Tb³⁺doping concentration does not change the crystal structure of NaBiF₄.In NaBiF₄:Tb³⁺,Sm³⁺phosphors,the energy transfer processes are from Bi³⁺to Tb³⁺and from Tb³⁺to Sm³⁺,in which the energy transfer of Tb³⁺-Sm³⁺ion is through quadrupole-quadrupole interaction.Excited by 352 nm UV light,NaBiF₄:Tb³⁺,Sm³⁺phosphors show strong white light emission.