Preparation And Properties Of Rare Earth Doped Alkaline Earth Metal Compound Phosphor Prowder For White LED

Rare earth luminescent materials are widely used in the field of illumination.As the fourth generation solid-state lighting source,LED is gradually replacing traditional lighting sources owing to its energy saving,environmental protection and high quality luminescent properties.Phosphor is one of the important components in phosphors converted white LEDs?pc-wLEDs?,and its properties have an important influence on the luminance,color rendering index,color temperature and lifetime of white LEDs.In this paper,several kinds of rare earth ions-doped alkaline earth metal composite phosphors were prepared by a sol-gel method and a solid reaction method.X-ray powder diffraction,field emission scanning electron microscopy,high power transmission electron microscopy,fluorescence spectroscopy,photoluminescence decay and UV-vis diffuse reflection,etc.,were uesd to characterize the phase behavior,morphology,luminescence properties of the prepared samples,and the corresponding luminescent mechanisms have been proposed tentatively in this dissertation.1.A series of Eu²⁺,Eu³⁺single-doped or co-doped Ca₃?PO₄?₂-LaPO₄ sosoloid phosphors with tunable luminescence were synthesized by a Pechini-type sol-gel method.X-ray diffraction?XRD?and Rietveld refinement results show that the Ca₃?PO₄?₂-LaPO₄ sosoloid phosphors are composed of Ca₃?PO₄?₂ and LaPO₄.The synthesized Ca₃?PO₄?₂-LaPO₄:Eu²⁺,Eu³⁺phosphor samples were mainly consisted of spherical particles with a particle size of 300-600 nm from SEM and HR-TEM analysis.Under the excitation of UV light,Ca₃?PO₄?₂-LaPO₄:Eu³⁺phosphor exhibit an orange-red luminescence coming from the characteristic emission of Eu³⁺?⁵D₀?⁷F_J J=0,1,2,3 transition?.ForCa₃?PO₄?₂-LaPO₄:Eu²⁺,Eu³⁺phosphor,it exhibits not only the orange-red emission of the Eu³⁺f-f characteristic transition,but also the blue-green emission of the Eu²⁺5d-4f characteristic transition.Further investigation indicates that there is an energy transfer from Eu²⁺to Eu³⁺in Ca₃?PO₄?₂-LaPO₄:Eu²⁺,Eu³⁺phosphor.Theluminescencecolorofthe Ca₃?PO₄?₂-LaPO₄:Eu²⁺,Eu³⁺phosphor can be tuned from orange red to white,green,blue-green by tuning the excitation wavelength of UV light from 260 to 310 nm.A white-light-emission has been obtained in Eu²⁺/Eu³⁺co-doped Ca₃?PO₄?₂-LaPO₄phosphor.When Ca²⁺in Ca₃?PO₄?₂-LaPO₄:Eu²⁺,Eu³⁺is replaced by Ba²⁺with a larger ionic radius,the characteristics emission of the Eu²⁺ion is blue-shifted,namely the emission peak region close blue region,and the corresponding excitation peak is also broadened toward the blue region.By adjusting the doping ratio and the impurity concentration,we achieved single-substrate white light emission in the Eu²⁺/Eu³⁺co-doped Ca₃?PO₄?₂-LaPO₄ phosphor.2.A series of Ce³⁺,Tb³⁺,Eu³⁺ions single doped or co-doped CLSO-LSO nanometer phosphors were synthesized by a sol-gel method.The XRD results show the pure phase of CLSO-LSO is calcined at 1100 ^oC,which is lower than that of by solid state reaction method?1200 ^oC?.It also can be seen clearly from XRD date that the CLSO-LSO solid solution phosphor prepared at 1100 ^oC conposed of Ca₂La₈?SiO₄?₆O₂ and La₂Si₂O₇ crystal phases.The SEM and HR-TEM images show that the prepared phosphor consists of spherical small particles with a particle size of100-200 nm.Under NUV light excitation,CLSO-LSO:Ce³⁺,Tb³⁺,Eu³⁺phosphors exhibit blue light emission of Ce³⁺?5d-4f transition?and green emission of Tb³⁺?⁵D₄?7F_J J=6,5,4,3 transitions?and orange red light emission of Eu³⁺?⁵D₀?⁷F_J J=0,1,2 transitions?.In the CLSO-LSO:Ce³⁺,Tb³⁺,Eu³⁺phosphors,the energy transfer mechanisms of Ce³⁺?Tb³⁺and Tb³⁺?Eu³⁺belong to quadrupole-quadrupole interactions.The luminescence color of CLSO-LSO:Ln³⁺(Ln³⁺=Ce³⁺,Tb³⁺,Eu³⁺)phosphors can betuned from blue to blue-green to white by adjusting the doping concentrations,types,and ratios of Ce³⁺,Tb³⁺,and Eu³⁺to some extent.3.A series of rare earth ion doped titanium niobate composite phosphors Ca₃Nb₂Ti₃O₁₄:Eu³⁺/Sm³⁺/Dy³⁺were prepared by a traditional high temperature solid state reaction method.XRD results show that the pure phase of Ca₃Nb₂Ti₃O₁₄ can be obtained when at 1300 ^oC.The doping of Eu³⁺,Sm³⁺and Dy³⁺does not affect the crystal structure of the matrix.Under the excitation of blue light at 466 nm,the Ca₃Nb₂Ti₃O₁₄:Eu³⁺phosphor show an orange-red luminescence,corresponding to the⁵D₀-⁷F₁?593 nm?and ⁵D₀-⁷F₂?612 nm?transitions of Eu³⁺.The luminescence color of Ca₃Nb₂Ti₃O₁₄:xEu³⁺phosphors can be tuned from yellow light to orange red light by varing the doping concentration of Eu³⁺.Under the excitation of violet light at 408 nm,the Ca₃Nb₂Ti₃O₁₄:Sm³⁺phosphor presents an orange red luminescence,corresponding to the ⁴G_5/2-⁶H_5/2?573 nm?,⁴G_5/2-⁶H_7/2?611 nm?and ⁴G_5/2-⁶H_9/2?658 nm?transition of Sm³⁺.The luminescence color of Ca₃Nb₂Ti₃O₁₄:ySm³⁺can be regulated from orange yellow to yellow light by varing the doping concentration of Sm³⁺Under the excitation of ultraviolet at353 nm,the Ca₃Nb₂Ti₃O₁₄:Dy³⁺phosphor shows a cool white luminescence corresponding to the ⁴F_9/2-⁶H_15/2?485 nm?and ⁴F_9/2-⁶H_13/2?574nm?transitions of Dy³⁺.The luminescence color of Ca₃Nb₂Ti₃O₁₄:zDy³⁺can be tuned from light yellow,white-cold,white light by varing the doping concentration of Dy³⁺to some extent.