Luminescent properties of Ca2SiO4：Eu^3＋ red phosphor for trichromatic white light emitting diodes

The luminescent properties of Eu^3＋doped Ca2SiO4 red phosphors synthesized by the flux fusion reaction method were investigated. It was found that the excitation spectrum included two regions： the weak excitation band below 325 nm and strong narrow peaks above 325 nm. The main peak of the excitation band was located at 400 nm. The peaks located at 290 nm were assigned to the combination of the charge transfer transition of O-Eu, peaks above 325 nm （325, 385, 400, 470, 511, and 539 nm） were assigned to the f-f transitions of Eu^3＋. The emission spectrum was dominated by the red peak located at 612 nm due to the electric dipole transition of ^5D0-^7F2. In addition, the effects of the Eu^3＋ content and charge compensators of Li^＋, Na^＋, K^＋, and Cl^- ions on the emission intensity were investigated. The experiment results suggested that the strongest emission was obtained when the concentration of the Eu^3＋ ions was 0.3 mol^-1, and Li^＋ ions gave the best improvement to enhance the emission intensity. Ca2SiO4：Eu^3＋, Li^＋ was thus suitable for low-cost trichromatic white light emitting diodes （WLED） based on UV InGaN chip.     

CaMoO_4∶Eu~(3+),M~+(M=Li,Na,K)粉体的制备与发光性能研究

采用溶胶-凝胶法制备了Ca_(1-1.5x)MoO_4∶xEu~(3+)和Ca_(0.5)MoO_4∶0.25Eu~(3+),M~+(M=Li,Na,K)荧光粉,并对样品的物相结构、颗粒形貌及发光性能进行了分析。结果表明,样品属于四方晶系,颗粒接近八面体形状,大小为2~3μm。激发光谱显示,样品的激发中心分别位于364 nm、386 nm、396 nm、419 nm和466 nm,最大激发峰值位于396 nm。在396 nm近紫外光激发下,样品的发射中心分别位于596 nm、616 nm、656 nm、704 nm,特征发射峰为616 nm,Eu3+离子掺杂浓度为25%(体积分数)时发光强度最强,引入的3种电荷补偿剂M~+(M=Li,Na,K)中,Li+对发光强度的提高最为显著。     

Properties of red-emitting phosphors Sr2MgSi2O7:Eu3+ prepared by gel-combustion method assisted by microwave

Novel red-emitting phosphors Sr2MgSi2O7:Eu3+ were prepared by gel-combustion method assisted by microwave. The phase struc-ture and luminescent properties of as-synthesized phosphors were investigated by XRD and fluorescence spectrophotometer, respectively. The results showed that the as-synthesized sample was Sr2MgSi2O7 with tetragonal crystal structure. The excitation spectrum of Sr2MgSi2O7:Eu3+ was composed of two major parts: one was the broad band between 200 and 350 nm, which belonged to the charge transfer of Eu3+-O2-; the other consisted of a series of sharp lines between 350 and 450 nm, ascribed to the f-f transition of Eu3+. The emission spec-trum consisted of two emission peaks at 593 and 616 nm, which was attributed to 5D0→7F1 and 5D0→7F2 of Eu3+, respectively. The concen-tration of Eu3+ (x) had great effect on the emission intensity of Sr2-xMgSi2O7:Eu3+x. When x varied in the range of 0.04-0.18, the intensity of emission peaks at 593 and 616 nm increased gradually with the concentration of Eu3+ increasing. It was interesting that no concentration quenching occurred. Moreover, the luminescent intensity could be greatly enhanced with incorporation of charge compensator Li+ ions.     

Luminescent characteristics of LiCaBO3：Eu^3＋ phosphor for white light emitting diode

LiCaBO3:Eu3+ phosphor was synthesized by high solid-state reaction method, and its luminescent characteristics were investigated. The emission and excitation spectra of LiCaBO3:Eu3+ phosphors exhibited that the phosphors could be effectively excited by near ultraviolet (400 nm) and blue (470 nm) light, and emitted red light. The effect of Eu3+ concentration on the emission spectrum of LiCaBO3:Eu3+ phos-phor was studied. The results showed that the emission intensity increased with increasing Eu3～ concentration, and then decreased because of concentration quenching. It reached the maximum at 3mol.% Eu3+, and the concentration self-quenching mechanism was the d-d interaction according to the Dexter theory. Under the conditions of charge compensator Li+, Na+ or K+ incorporated in LiCaBO3, the emission intensities of LiCaBO3:Eu3+ phosphor were enhanced.     

A novel red phosphor:Ca2GeO4:Eu3+

A novel red phosphor Ca2GeO4:Eu3+ was prepared by the traditional solid state reaction. X-ray powder diffraction (XRD) analysis suggested that there was no impurity phase. The study on the diffusion reflection spectra of the undoped and Eu3+ doped Ca2GeO4 phosphors revealed an absorption band superposed of that of the host material and the Eu3+ ions. And the excitation spectrum presented a dominating broad band at 250–300 nm which was attributed to both the host material absorption and the charge transfer band (CTB) of the Eu3+ ions. The investigation on the excitation and diffusion spectra showed that there was an effective energy transfer from the host material to the Eu3+ ions. This was favorable to the red emission of the phosphor. Photoluminescence measurements indicated that the phosphor presents bright red emission at 611 nm under UV excitation. In addition, the Al3+ or Li+ codoping enhanced the red emission from Ca2GeO4:Eu3+ by about 3 and 2 times respectively under UV excitation.     

Eu3+激活的Li2Gd4（MoO4）7钼酸盐红色荧光体及其发光性质

由高温固相反应首次合成Li2(Gd1-xEux)4(MoO4)7(0相似文献   

Luminescent properties of Eu³⁺-doped BaZrO₃ phosphor for UV white light emitting diode

A novel orange phosphor Eu3+ doped barium zirconate(BaZrO3) was synthesized by conventional solid state reaction method and its crystal structure and luminescent properties were investigated in this paper.The X-ray diffraction patterns(XRD) showed that simple BaZrO3 phase was obtained.Monitoring at 596 nm,the excitation spectrum consisted of a broad band and a series of narrow bands and the stronger excitation peaks located at 275 and 393 nm,respectively.The emission spectrum excited by 393 nm UV light was composed of four narrow bands.The strongest emission was located at 596 nm.The appropriate concentration of Eu3+ was 0.025(molar fraction) for the highest emission intensity at 596 nm.The H3BO3 and ammonium were added as flux and the results showed that 2 wt.% NH4F ions was the optimal flux for BaZrO3:Eu3+.     

Luminescent properties of red phosphors K2Ba（MoO4）2：Eu3＋ for white light emitting diodes

K2Ba(MoO4)2:Eu3+ phosphors were synthesized by solid-state reaction. The emission and excitation spectra of K2 Ba(MoO4)2:Eu3+ phosphors exhibited that the phosphors could be effectively excited by near ultraviolet (394 nm) and blue (465 nm) light, and emitted red light at 616 nm. The influence of Eu3+concentration, sintering temperature and charge compensators (K+, Na+ or Li+ ) on the emission intensity were investigated. The results indicated that concentration quenching of Eu3+ was not observed within 30mol.% Eu 3+, 600 oC was a suitable sintering temperature for preparation of K2 Ba(MoO4)2:Eu3+phosphors, and K+ ions gave the best improvement to enhance the emission intensity. The CIE chromaticity coordinates of K2 Ba(MoO4)2:0.05Eu3+phosphor were calculated to be (0.68, 0.32), and color purity was 97.4%.     

Spectral Properties and Sensitization of Ce3+ and Eu2+ Codoped Calcium Zinc Chlorosilicate

ＳｐｅｃｔｒａｌＰｒｏｐｅｒｔｉｅｓａｎｄＳｅｎｓｉｔｉｚａｔｉｏｎｏｆＣｅ３＋ａｎｄＥｕ２＋ＣｏｄｏｐｅｄＣａｌｃｉｕｍＺｉｎｃＣｈｌｏｒｏｓｉｌｉｃａｔｅＬｉｎＨａｉ（林海），ＬｉｕＸｉｎｇｒｅｎ（刘行仁），ＺｈａｎｇＸｉａｏ（张晓）（Ｃｈａ...     

Luminescent properties of MMgP_2O_7：Eu~（3＋）（M=Ca,Sr,Ba） phosphor

A series of red phosphors Eu3+-doped MMgP2O7(M=Ca,Sr,Ba) were synthesized by solid-state reaction method.X-ray powder diffraction(XRD) analysis confirmed the formation of pure CaMgP2O7,SrMgP2O7 and BaMgP2O7 phase.Photoluminescence spectra of MMgP2O7(M=Ca,Sr,Ba):Eu3+ phosphors showed a strong excitation peak at around 400 nm,which was coupled with the characteristic emission(350-400 nm) from UV light-emitting diode.The CaMgP2O7:Eu3+,SrMgP2O7:Eu3+ and BaMgP2O7:Eu3+ phosphors showed strong emission bands peaking at 612,593 and 587 nm,respectively.Due to the difference of the ion sizes between Ba2+(0.142 nm),Sr2+(0.126 nm),Ca2+(0.112 nm),Mg2+(0.072 nm) and Eu3+(0.107 nm),Eu3+ ions were expected to substitute for different sites in CaMgP2O7,SrMgP2O7 and BaMgP2O7 lattice.     

Combustion synthesis of Ce~（3＋）, Eu~（3＋） and Dy~（3＋） activated NaCaPO_4 phosphors

The preparation of NaCaPO4 doped with rare earth (RE) ions Ce3+, Eu3+ and Dy3+ by combustion method was described. Under UV excitation (251 nm) of NaCaPO4:Ce3+ showsd emission (367 nm) in UV range. When NaCaPO4:Dy3+ phosphor was excited at 349 nm, the emission spectrum showed intense bands at 482 nm (blue) and 576 nm (yellow). In Eu activated NaCaPO4 phosphor, the emission spectrum showed a dominant peak at 594 nm (orange) while others were at 614 and 621 nm (red) when excited at 393 nm. The prepared phosph...     

Luminescence characteristics of Ca_4YO(BO_3)_3 doped with Bi~(3+),Dy~(3+) and Pr~(3+) ions

The photoluminescence(PL) properties of Ca4YO(BO3)3 doped with Bi3+,Dy3+,and Pr3+ ions were investigated.These compounds were prepared using a typical solid-state reaction.The excitation and emission spectra were measured using a spectrofluorometer.For Ca4YO(BO3)3:Bi3+,the excitation spectrum showed the bands at about 228,309,and 370 nm which correspond to the 1S0→1P1 transition and the 1S0→3P1 transition of Bi3+ ions.The emission band at 390 nm corresponded to the 3P1→1S0 transition of Bi3+ ions.For Ca4YO(BO3)3:Bi3+,Dy3+,energy transfer occurred from Bi3+ to Dy3+ somewhat.In Ca4YO(BO3)3:Bi3+,Dy3+,Pr3+,the excitation band at 367 nm was enhanced obviously due to the energy migration from Bi3+ to Pr3+,which converted efficiently the emission of semiconductor InGaN based light-emitting diode(LED).Therefore,the emission of Dy3+ ions was enhanced due to the energy migration from the process of Bi3+→Pr3+→Dy3+.It resulted in the good color rendering.     

Luminescence and Preparation of LED Phosphor Ca8Mg(SiO4)4Cl2:Eu2+

Calcium magnesium chlorosilicate doped by europium, Ca8Mg(SiO4)4Cl2:Eu2 , was prepared by the solid state reaction at high temperature. The compound obtained is pure Ca8Mg(SiO4)4Cl2 phase with cubic structure. Its average particle size is 5 μm, and it has good dispersity and morphological form. The excitation spectrum of Ca8Mg(SiO4)4Cl2:Eu2 is a wide band, which covers from 270 to 480 nm. The emission spectrum is also a wide band peaked at 510 nm. The luminescent intensity reaches to the maximum when the concentration of Eu2 is 2%. The wavelength of emission and excitation of the phosphor with various Eu2 contents keeps constant. This spectrum range matches violet and blue LED chips very well, and its strong luminescence intensity is suitable for a green phosphor of tricolor phosphor of white light LED.     

Synthesis and luminescence properties of europium activated Ca3Al2O6-Sr3Al2O6 system

Divalent europium activated tristrontium dialuminum hexaoxide phosphor, (Sr1-xEux)3Al2O6, was obtained by solid state reaction. Crystal structure and luminescence properties of synthesized (Sr1-xEux)3Al2O6 were investigated. The major excitation band of (Sr1-xEux)3Al2O6 located in blue light region, the photoluminescence spectrum showed red light emission peaked at 618 nm which could be attributed to the d-f transition of the Eu2+. The influence of Ca2+ substitution for Sr2+ on structural and luminescence properties of Eu2+ doped Sr3Al2O6 was also studied. The photoluminescence peak position of (Sr1-yCay)2.94Eu0.06Al2O6 varied from 618 to 655 nm with increasing y value. The reason for redshift in the emission band of (Sr1-yCay)2.94Eu0.06Al2O6 phosphor was also discussed.     

Intense blue-emitting Ca₂PO₄Cl:Eu²⁺ phosphor for near-ultraviolet converting white light-emitting diodes

A blue phosphor Ca2PO4Cl:Eu2+(CAP:Eu2+) was synthesized by solid state reaction.The Ca2PO4Cl:Eu2+ exhibited high quantum efficiency and excellent thermal stability.The luminescent intensity of Ca2PO4Cl:Eu2+ was found to be 128% under excitation at 380 nm,149% under 400 nm,and 247% under 420 nm as high as that of BaMgAl10O17:Eu2+.The optimal doping concentration was observed to 11 mol.% of CAP:Eu2+.The energy transfer between Eu2+ ions in CAP were occurred via electric multipolar interaction,and the critical transfer distance was estimated to be 1.26 nm.A mixture of blue-emitting Ca2PO4Cl:Eu2+,green-emitting(Ba,Sr)2SiO4:Eu2+ and red-emitting CaAlSiN3:Eu2+ phosphors were selected in conjunction with 400 nm chip to fabricate white LED devices.The average color-rendering index Ra and correlated color temperature(Tc) of the white LEDs were found to be 93.4 and 4590 K,respectively.The results indicated that it was a promising candidate as a blue-emitting phosphor for the near-UV white light-emitting diodes.     

Preparation and Fluorescent Property of Eu-Doped High Silica Glasses

A method to fabricate europium ions doped-high silica glass for transparent fluorescence materials based on the fabrication and sintering technique of nano-porous silica glass was reported. Glasses impregnated with Eu ions and sintered at above 1150 ℃ in a reduction atmosphere show a very strong blue light from an emission band at about 430 nm due to the 4f65d→4f7(8S7/2) transition of the Eu2 ions. On the other hand, the Eu-doped glass obtained by co-impregnated with Y3 and V5 ions and sintering in oxidation atmosphere behaves a very strong red emission band at about 615 nm with a UV excitation. An appearance of vanadate band in the excitation spectrum of Eu3 , Y3 and V5 ions co-doped high silica glass implies an effective energy transferring from VO43- to Eu3 and effective excitation of Eu3 by about 500 nm strong broad emission of VO43-.     

Study on Red Long-Time Luminescent Material Y2O2S:Eu,M (M = Mg,Ca, Sr,Ba)

The red long-time luminescent material Y₂O₂S:Eu³⁺, M (M = Mg, Ca, Sr, Ba) was prepared by high temperature solid-state method. The XRD result of the sample showed that the crystal phase was Y₂O₂S, which belong to hexagonal system, and no new crystal phase were by doping different amount of Mg, Ca, Sr, Ba. The excitation spectrum was a broad band within 200 × 400 nm region, the characteristic peaks of emission spectrum were located at 583, 595, 597, 617, 627, 707 nm. There was no marked change in excitation spectra, emission spectra and maximum of their wavelengths of the luminescent materials by doping with different ions. The luminescent intensity of the phosphors were stronger when the concentration of doping ions was Mg/Y = 6%, Ca/Y = 4%, Sr/Y = 8%, Ba/Y = 2.5%, respectively. Its sequence of luminescent intensity from high to low is Sr > Ba > Mg > Ca.     

Enhancement of red to orange emission ratio of YPO4：Eu3＋,Ce3＋ and its dependence on Ce3＋ concentration

Eu3+ and Ce3+ co-doped YPO4 microspheres were synthesized by hydrothermal method without template. The emission spectra showed that the red emission centered at 618nm could be readily increased relatively to the orange emission centered at 590nm by controlling the doping concentration of Ce3+ ion. The investigation based on excitation spectra and decay curves demonstrated that the doped Ce3+ ions took two efficient energy transfers to Eu3+ ions and affected the lifetime of the emission states of Eu3+ ions so that the emission spectra of Eu3+ ion were accordingly tuned with the Ce3+ content increasing. This controllable red (5D0→7F2) to orange ( 5D0→7F1) emission ratio of YPO4:Eu3+,Ce3+ made it very promising for encoded anti-fake labels and bio-labels.     

Luminescence properties of BaB8O13：Eu under UV and VUV excitation

The phosphor BaB8O13:Eu3+ were synthesized by solid-state reaction, and their luminescent properties were studied under 254 and 147 nm excitation. The excitation spectrum showed two broad bands in the range of 100-300 nm: one was the host lattice absorption with the maxima at 160 nm and the other was Ba-O absorption overlapped with the CT band of Eu3+, which indicated that the energy of the host lat-tice absorption could be efficiently transferred to the Eu3+. The overlapped bands were tended to separate when monitored by different wave-length, which indicated that at least two Ba2+ sites were available in BaB8O13. The emissions of Eu3+ (612 nm) and Eu2+ (405 nm) were both observed in the emission spectra of BaB8O13:Eu3+ under the excitation of either 254 or 147 nm. With the doping concentration of Eu3+ in-creasing, the 612 nm emission was enhanced while 405 nm emission was decreased under 254 nm excitation, which was due to the persistent energy transfer from Eu2+ to Eu3+. While under 147 nm excitation, the 612 nm emission was quenched and the 405 nm emission was en-hanced. It was concluded that the preferential excitation of Eu2+ under 147 nm excitation was one of the reasons for this facts.     

白光LED用LaPO4:Eu3+红色荧光粉的合成与表征

利用水热法制备了性能稳定的红色荧光粉LaPO4:Eu3+,同时研究了不同的Eu3+浓度、煅烧温度对荧光粉发光性能的影响.通过X射线粉末衍射(XRD)和扫描电子显微镜(SEM)来表征荧光粉的晶体结构和颗粒大小及形貌;用激发光谱和发射光谱以及荧光衰减曲线来表征荧光粉的荧光性能.结果表明:未煅烧时前躯体主要是六方晶相LaPO4·0.5H2O,煅烧温度在900℃时,所制备样品为单斜相LaPO4:Eu3+;SEM图像显示5 at.%Eu3+掺杂LaPO4呈椭球形,颗粒长约为500 nm,宽约为300 nm.最大发射波长和激发波长分别为592 nm和393 nm,发射光谱中592 nm和612 nm的发射峰对应的是Eu3+离子的5D0→7F1和5D0→7F2跃迁.其荧光寿命为3.32 ms.