新型SrCaWO_4:Eu~(3+)荧光粉的制备、电子结构及其发光性能
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摘要
采用一种较为温和的水热法成功地制备出一种新型白光LED用红色Sr_yCa_(1-x-y)WO_4:xEu~(3+)(x=0,0.05;y=0,0.01,0.02,0.03,0.05)荧光粉,基于第一性原理对CaWO_4和Sr_(0.02)Ca_(0.98)WO_4的电子结构进行了理论分析,通过X射线衍射、Rietveld精修和荧光光谱对样品的物相结构和发光性能进行了研究。计算结果表明:CaWO_4、Sr_(0.02)Ca_(0.98)WO_4晶体都是一种直接带隙半导体,禁带宽度分别为4.077eV和4.080eV.XRD和精修结果表明了所制备的荧光粉是空间群为I41/a(88)纯四方相的白钨矿结构,Eu~(3+)和Sr~(2+)成功的掺杂到CaWO_4晶格中取代了Ca位.荧光光谱结果表明:当x=0.05,y=0.02时,Sr_yCa_(1-x-y)WO_4:xEu~(3+)系列荧光粉在617nm处Eu~(3+)的~5D_0→~7F_2电偶极跃迁发射最强,并且在近紫外(397nm)和蓝光区域(467nm)处都能被有效激发,Sr~(2+)引入到CaWO_4:0.05Eu~(3+)中可以通过改变Eu~(3+)格位周围对称性从而增强红光发射.这些结果表明Sr_(0.02)CaWO_4:0.05Eu~(3+)荧光粉可以作为一种有前景的白光LED用红色荧光粉.
A series of new red Sr_yCa_(1-x-y)WO_4:xEu~(3+) (x=0,0.05;y=0,0.01,0.02,0.03,0.05)phosphors of white LEDs were successfully prepared by a mild hydrothermal method.The electronic structure of CaWO_4 and Sr_(0.02)Ca_(0.98)WO_4 was calculated and analyzed by firstprinciples.The phase structure and luminescence properties of the samples were studied by X-ray diffraction,Rietveld refinement and fluorescence spectroscopy.The calculation results show that the CaWO_4 and Sr_(0.02)Ca_(0.98)WO_4 crystals are all direct band gap semiconductors with band gaps of 4.077 eV and 4.080 eV,respectively.XRD and Rietveld refinement show that the prepared phosphors is a scheelite structure with a space group of I41/a(88)pure tetragonal phase.Eu~(3+) and Sr~(2+) are successfully doped into the CaWO_4 lattice to replace the Ca site.Fluorescence spectroscopy results show that the Sr_yCa_(1-x-y)WO4:xEu~(3+) phosphors emit the strongest ~5D_0→~7F_2 electric dipole transition of Eu~(3+) at 617 nm when x=0.05,y=0.02.Meanwhile,it can be effectively excited in the near ultraviolet(397 nm)and blue regions(467 nm).And the introduction of Sr~(2+) into CaWO_4:0.05 Eu~(3+) will change the symmetry around the Eu~(3+) lattice to enhance red emission.These results indicate that the phosphor is a promising red phosphor for use in W-LEDs.
A series of new red Sr_yCa_(1-x-y)WO_4:xEu~(3+) (x=0,0.05;y=0,0.01,0.02,0.03,0.05)phosphors of white LEDs were successfully prepared by a mild hydrothermal method.The electronic structure of CaWO_4 and Sr_(0.02)Ca_(0.98)WO_4 was calculated and analyzed by firstprinciples.The phase structure and luminescence properties of the samples were studied by X-ray diffraction,Rietveld refinement and fluorescence spectroscopy.The calculation results show that the CaWO_4 and Sr_(0.02)Ca_(0.98)WO_4 crystals are all direct band gap semiconductors with band gaps of 4.077 eV and 4.080 eV,respectively.XRD and Rietveld refinement show that the prepared phosphors is a scheelite structure with a space group of I41/a(88)pure tetragonal phase.Eu~(3+) and Sr~(2+) are successfully doped into the CaWO_4 lattice to replace the Ca site.Fluorescence spectroscopy results show that the Sr_yCa_(1-x-y)WO4:xEu~(3+) phosphors emit the strongest ~5D_0→~7F_2 electric dipole transition of Eu~(3+) at 617 nm when x=0.05,y=0.02.Meanwhile,it can be effectively excited in the near ultraviolet(397 nm)and blue regions(467 nm).And the introduction of Sr~(2+) into CaWO_4:0.05 Eu~(3+) will change the symmetry around the Eu~(3+) lattice to enhance red emission.These results indicate that the phosphor is a promising red phosphor for use in W-LEDs.
引文
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[3]刘行仁.白光LED固态照明光转换荧光体[J].发光学报,2007,28(3):291-301.
[4]Xia Z,Liu Q.Progress in discovery and structural design of color conversion phosphors for LEDs[J].Progress in Materials Science,2016,84:59-117.
[5]洪广言.稀土发光材料[M].北京:科学出版社,2011.
[6]Xu M,Wang L,Liu L,et al.Influence of Gd3+doping on the luminescent of Sr2P2O7:Eu3+orange-red phosphors[J].Journal of Luminescence,2014,146(1):475-479.
[7]Zhai Y,Zhang W,Yin Y,et al.Morphology tunable synthesis and luminescence property of NaGd(MoO4)2:Sm3+microcrystals[J].Ceramics International,2016,43(1):841-846.
[8]周鹤,周志勇,曾群,等.溶胶-凝胶法制备Li1.0Nb0.6Ti0.5O3:Eu3+红色荧光粉[J].发光学报,2018,39(7):909-914.
[9]Huang X,Li B,Guo H,et al.Molybdenum-doping-induced photoluminescence enhancement in Eu3+-activated CaWO4red-emitting phosphors for white light-emitting diodes[J].Dyes&Pigments,2017,143:86-94.
[10] Wei B,Liu Z,Xie C,et al.Fast synthesis of red Li3BaSrLn3(WO4)8:Eu3+phosphors for white LEDs under near-UV excitation by a microwave-assisted solid state reaction method and photoluminescence studies[J].Journal of Materials Chemistry C,2015,47(3):12 322-12 327.
[11]Su Y,Li L,Li G.Synthesis and optimum luminescence of CaWO4-based red phosphors with co-doping of Eu3+and Na+[J].Chemistry of Materials,2008,20:6 060-6 067.
[12]王林香.Na+,Li+,Bi 3+掺杂CaWO4:Eu3+荧光粉的制备及发光特性[J].高等学校化学学报,2018,39(1):25-31.
[13]宋杨.Dy3+/Eu3+掺杂钨钼酸盐微纳结构可控制备与发光机制研究[D].西安:西安理工大学,2016.
[14]Dong W K,Cho I S,Shin S S,et al.Electronic band structures and photovoltaic properties of MWO4,(M=Zn,Mg,Ca,Sr)compounds[J].Journal of Solid State Chemistry France,2011,184(8):2 103-2 107.
[15]李桂芳,杨倩,卫云鸽.复合钙钛矿型NaLaMgWO6:Eu3+红色荧光材料的制备及发光性能研究[J].无机材料学报,2017,32(9):936-942.
[16]Blasse G.Energy transfer in oxidic phosphors[J].Physics Letters A,1968,28(6):444-445.
[17]Liang Z,Mu Z,Wang Q,et al.The synthesis and luminescence properties of a novel red-emitting phosphor:Eu3+-doped Ca9La(PO4)7[J].Applied Physics A,2017,123(10):612.
[18]Su J,Mi X,Sun J,et al.Tunable luminescence and energy transfer properties in YVO4:Bi 3+,Eu3+,phosphors[J].Journal of Materials Science,2017,52(2):782-792.