| White light emitting diodes(W-LED),due to environmental freidliness,non-toxicity and all solid state,have become a new generation of solid-state light source.It has good applications foreground in the filds of illumination and display.Therefore,it has practical significance to develop a white LED phosphor with good luminous stability and efficiency.Among the rare earth luminescent material matrix,the molybdate materials have good physical and chemical stability and can absorb ultraviolet light.Therefore,by dopping rare earth ions(Eu3+ and Tb3+),it was expected to obtain a single matrix white light emission under the excitation of the ultraviolet LED chips.In this paper,Binary Molybdate Li2Zn2(MoO4)3,.Na2Zn5(MoO4)6 and K4Zn(MoO4)3 were selected as the matrix materials,Eu3+,and Tb3+ were used as activators,a series of phosphors that can emit red,green and white light,were synthesized respectively.The stability,phase composition and luminescence properties of the phosphors were determined by DTA-TAG,IR,XRD and fluorescence spectrum.Eu3+ doped Li2Zn2(MoO4)3 phosphors and Eu3+/Tb3+ co-doped Li2Zn2(MoO4)3 phosphors were synthesized by Gel-combustion method.And the effect of some influencing factors have researched,such as the pH of solution(pH= 1,3,5,7,9),the ratio of metal ions to citric acid(C/M= 1:1,1.5:1,2:1,2.5:1),and the calcination temperature(550 ?,600 ?,650 ?,700 ?,750 ?).However,in different preparation conditions have had no effect on phase composition of matrix,Li2Zn2(MoO4)3 belongs to Orthorhombic lyonsite-type structure,Pnma space group.When x was between 1%and 4%in Li2Zn2(MoO4)3:xEu3+,yTb3+phosphors,white light emission could be obtained in the doping range of y=x?12%Tb3+according to the Eu3+doping range,by the excitation of ultraviolet light(308 nm).It was indicated that the co-doping of Eu3+ and Tb3+ with the substrate could obtain adesired wide range white light-emitting phosphors.Its optimal CIE coordinate was(0.330,0.310),which was close to the National Television Standards Committee NTSC standard white light color coordinates(0.330,0.330).The energy transfer between the matrix and Eu3+ and Tb3+ has investigated by studying the luminescence properties of Li2Zn2(MoO4)3:xEu3+,yTb3+ under different conditions.Eu3+/Tb3+ doped Na2Zns(MoO4)6 series phosphors were synthesized by Gel-combustion method.The pH of solution,the ratio of metal ions to citric acid and the calcination temperature have had no effect on phase composition,Na2Zn5(MoO4)6 belongs to a single phase of Triclinic-single Crystal,Pi space group.Na2Zn5(MoO4)6:xEu3+,yTb3+ could get wide range of white light emission by the excitation of ultraviolet light(299nm).As the doping amount of Eu3+ increases,the CIE coordinates of the phosphors have moved from white light to orange light.The energy transfer between MoO42-and Eu3+and Tb3+ has investigated by studying the luminescence properties of Li2Zn2(MoO4)3:xEu3+,yTb3+under different conditions.Eu3+,Tb3+ doped K4Zn(MoO4)3 phosphors were synthesized by Gel-combustion method.In different preparation conditions have had no effect on phase composition,K4Zn(MoO4)3 belongs to a single phase of Orthorhombic,Pnma space group.The K4Zn(MoO4)3:xEu3+ y%Tb3+phosphors were excited by ultraviolet light(383 nm).When x= 1%,y= 10%,its CIE coordinate was(0.235,0.232),which was located in the blue region;When x= 3%,y = 10%,its CIE coordinate was(0.292,0.269),which was located in the white region.Blue light removed to white light,which has been achieved.The energy transfer between MoO42-and Eu3+ and Tb3+ has investigated by studying the luminescence properties of K4Zn(MoO4)3:xEu3+,yTb3+under different conditions.In this paper,Binary Molybdate Li2Zn2(MoO4)3,Na2Zns(MoO4)6 and K4Zn(MoO4)3.were selected as the matrix,Eu3+ and Tb3+ were used as activators,a series of phosphors which have the stable physical chemical properties,good luminescence properties and performing red,green and white emission.Compared with this three white LED phosphors,Li2Zn2(MoO4)3:Eu3+,Tb3+revealed wider range and higher stability of white light emission. |
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