The Luminescence Research Of Rare Earth (Eu³⁺, Eu²⁺,Tb³⁺) Doped Three Primary Colors Phosphors For White Light-emitting-diodes（w-LEDs）

The rare earth （RE） doped molybdenum borate, orthophosphate and silicatematerials are all important part of the luminescence materials. Eu³⁺, Eu²⁺/Mn²⁺and Ce³⁺/Tb³⁺are widely used in the luminescent materials as dopants. Due to the ultraviolet/near-ultraviolet （UV/n-UV） luminescence properties and good stability of these hostmaterials, they obtain a lot of attention on the display and illumination field. Then, theresearch in luminescent properties of RE doped luminescence materials is valuable forsearching suitable phosphors for white light-emitting-diodes（w-LEDs）.In this paper, rare earth ions Eu³⁺, Eu²⁺/Mn²⁺, and Ce³⁺/Tb³⁺as the dopants, andEu₂MoB₂O₉, Ba₂MgP₄O₁₃and CaGd4Si3O13as the host materials are selected. Thesematerials are prepared by high temperature solid-state reaction method. The structureand luminescent properties of the three kinds of materials are measured respectively; themechanisms of emission are talked out; the chromaticity coordinates and decay curvesof the emission under the UV/n-UV excitation have been analyzed; and the potentialapplications are discussed.In the third chapter, the preparation process of Eu³⁺ions fully concentratedEu₂MoB₂O₉is stated. Through the test of X-ray diffraction （XRD）, the structure and thefeatures of the phosphors are represented. In the excitation spectra, the broad absorptionband in the n-UV region （250-350nm） originates from the charge transfer （CT）transition of O2-�'Eu³⁺. The sharp absorption peaks between350and550nm are due tothe f–f transition of the4f9level of Eu³⁺ions. The n-UV emission spectra and CIEchromaticity coordinates indicate that Eu₂MoB₂O₉phosphor can emit bright redluminescence with a large dominated peak at around615nm attributed to the electricdipole transition of5D0�'7F2.The decay curve and temperature dependent luminescence under the n-UV excitation of Eu₂MoB₂O₉are discussed. The results above indicate thatEu₂MoB₂O₉can be effectively excited by near ultraviolet light, which well matches theemission wavelength of n-UV LED chips and could be further tested as a potentialred-emitting phosphor for application on the n-UV chip based white LEDs.In the forth chapter, XRD test is also used to make sure the materials obtained arepure Ba₂MgP₄O₁₃:Eu²⁺. According to the excitation spectra, the absorption peaks areascribed to the4f-5d transition of Eu²⁺. And the emission spectra and CIE chromaticitycoordinates show that Ba₂MgP₄O₁₃:Eu²⁺have a bright blue luminescence with a peakwavelength at409nm, which originates from the allowed4f65d1�'4f7electric dipoletransition of Eu²⁺at the Ba²⁺site in the lattice. The decay curve and temperaturedependent luminescence under the n-UV excitation of Ba₂MgP₄O₁₃:Eu²⁺are discussed.The results above indicate that Ba₂MgP₄O₁₃:Eu²⁺is suitable to be excited by n-UVlight matched with the UV-LED chips and could be further investigated for its potentialapplication as a blue-emitting phosphor for n-UV based white LEDs.In the fifth chapter, the results of XRD test confirm that the pureCaGd4Si3O13:Ce³⁺、CaGd4Si3O13:Tb³⁺、CaGd4Si3O13:(Ce³⁺,Tb³⁺) are prepared. Theexcitation and emission spectra of CaGd4Si3O13:Ce³⁺、 CaGd4Si3O13:Tb³⁺、CaGd4Si3O13:(Ce³⁺,Tb³⁺) are discussed. The results show that the efficient energy fromCe³⁺to Tb³⁺could take place in CaGd4Si3O13:(Ce³⁺,Tb³⁺) and Ce³⁺ions have an effectsensitization to Tb³⁺. According to the emission spectra, the emission ofCaGd4Si3O13:Tb³⁺and CaGd4Si3O13:(Ce³⁺,Tb³⁺) are green and the emission ofCaGd4Si3O13:Ce³⁺is blue.In the sixth chapter, the results of XRD test show that pure Ba₂MgP₄O₁₃:Mn²⁺andBa₂MgP₄O₁₃:(Mn²⁺,Eu²⁺) are prepared. The emission spectra ofBa2Mg1-xMnxP4O13（x=0.01-0.85） show a broad emission centered at610nm, due to the4T1–6A1transition of Mn²⁺ions substituting Mg²⁺sites. In the excitation spectra, theexcitation bands are attributed to the d–d transitions of Mn²⁺. The luminescence spectraof Eu²⁺and Mn²⁺co-doped phosphors Ba1.94Eu0.06Mg1-xMnxP4O13（x=0-0.12） show thatwhen the concentration of the Mn²⁺activator is altered, no shift of red-emission peak is observedand effective energy transfer from Eu²⁺to Mn²⁺takes place. The temperature dependentluminescence spectra of Ba1.94Eu0.06Mg1-xMnxP4O13（x=1.0） and the decay curves of thetwo kinds of phosphors are discussed. The CIE coordinates of the Ba1.94Eu0.06Mg1-xMnxP4O13（x=0-0.15） phosphors vary UV to deep red for different xvalue. It is believed that the phosphor Ba1.94Eu0.06Mg1-xMnxP4O13（x=0-0.15） has thepotential application of being a new red phosphor for w-LED by controlling the Mn²⁺doping concentrations.The novelties of the dissertation are the following: the rare earth （RE） Eu³⁺, Eu²⁺,Ce³⁺and Tb³⁺ions respectively doped molybdenum borate, orthophosphate and silicatematerials are prepared. Their excitation and emission spectra, decay curves,temperature dependent luminescence spectra and the CIE coordinates are allresearched systemly. The mechanisms of the emission are discussed, and the potentialvalue of the application in display and illumination fields is respected.