Luminescent characteristics of Ba3Y2（BO3）4：Eu^3＋ phosphor for white LED

The Ba3Y2（BO3）4：Eu^3＋ phosphor was synthesized using a high temperature solid-state reaction method and the luminescent characteristics were investigated. The emission spectrum exhibited one strong red emission at 613 nm, corresponding to the electric dipole 5D0-TF2 transition of Eu^3＋, under 365 nm excitation. The excitation spectrum of 613 nm indicated that the Ba3Y2（BO3）n：Eu^3＋ phosphor was effectively excited by ultraviolet （UV） （254, 365 and 400 nm） and blue （470 nm） light. The effect of Eu^3＋ concentration on the 613 nm emission of the Ba3Y2（BO3）n：Eu^3＋ phosphor was measured. The results showed that the emission intensity increased with increasing Eu^3＋ concentration, and then decreased. The CIE color coordinates of Ba3Y2（BO3）4：Eu^3＋ phosphor were x=0.641 and y=0.359 at 15 mol.% Eu^3＋.     

Vacuum ultraviolet excited photoluminescence properties of Gd2O2CO3：Eu^3＋ phosphor

The Gd2O2CO3：Eu^3＋ with type-Ⅱ structure phosphor was successfully synthesized via flux method at 400 ℃ and their photoluminescence properties in vacuum ultraviolet （VUV） region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO3^2- host absorption and charge transfer （CT） of Gd^3＋-O2^- were observed for Gd2O2CO3：Eu^3＋. Under 172 nm excitation, Gd2O2CO3：Eu^3＋ exhibited strong red emission with good color purity, indicating Eu^3＋ ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3：Eu^3＋ was （x=0.652, y=0.345）. The photoluminescence quenching concentration of Eu^3＋ excited by 172 nm for Gd2O2CO3：Eu^3＋ was about 5%. Gd2O2CO3：Eu^3＋ would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.     

Synthesis and Properties of Eu Activated Strontium Molybdate Phosphor

In order to prepare fluorescent material for white Light Emitting Diodes （LEDs）, a new Eu^3＋ activated molybdate phosphor SrMoO4 was fabricated with solid-state method. X-ray diffraction （XRD） showed that the doping of trivalent europium ion reduced the lattice parameters. The excitation and emission spectra indicated that this phosphor could be excited effectively by the visible light, and then emitted red light with the peaks located at 616 and 624 nm. The influence of Eu^3＋ concentration on the luminescent properties of Eu^3＋ doped SrMoO4 was investigated and the 25% （mole fraction） was the appropriate molar concentration. The reaction time and temperature had obvious effect on the luminescent properties. The luminescent intensity reached the strongest when it was sintered at 800 ℃ for 3 h.     

Luminescence properties of nitride red phosphor for LED

Eu^2＋-doped ternary nitride phosphor, Sr2Si5N8：Eu^2＋, was synthesized using the high temperature solid-state method. The X-ray diffraction （XRD） pattern showed that Sr2Si5N8 single phase was obtained. The lattice parameters shrank because the radius of Eu^2＋ was smaller than that of Sr^2＋. The emission spectra showed a broad emission band. With an increase in Eu^2＋ concentration, the emission peak position was redshifted. The excitation spectra showed two excitation bands originating from the host and the 4f^7→4f^6 5d^1 transition of Eu^2＋ ions Compared with the luminescent characteristic of Sr2Si5N8：Eu^2＋ and CaS：Eu^2＋ phosphors, at different temperatures, it was noted that the intensity of the two phosphors reduced gradually with an increase in temperature. The intensity of Sr2Si5N8：Eu^2＋ phosphor was stronger than that of CaS：Eu^2＋, which indicated that the luminescent characteristic of the former was better than that of the latter.     

Luminescence enhancement of BaMgSiO4：Eu^2＋ by adding borate as flux

The luminescence of EU^2＋ in BaMgSiO4 with BaB2O4 as flux was studied. The emission spectrum of the phosphor consisted of two bands, peaking at about 398 nm and 515 nm, which were attributed to the emissions from different Eu^2＋ sites in the lattice. When the BaB2O4 flux was applied, the intensity of the 398 nm emission was not clearly affected, but the intensity of the 515 nm emission was enhanced by about ten times. Gaussian fitting showed that the emission band at around 515 nm could actually be resolved into two bands with peak wavelengths of 499 nm and 521 nm, respectively. The assignments of the emission bands to the cation sites were carried out according to the values of bond valence. The overlapping of the 398 nm emission band on the excitation band of 515 nm emission implied that energy transfer could occur from the luminescent center related to the 398 nm emission to the center related to the 515 nm emission, and the energy transfer process remarkably enhanced the intensity of the 515 nm emission band. The phosphor had strong excitation at around 350-400 nm and emitted a bright green luminescence. Thus it could have applications as a green component in solid-state lighting devices assembled by near-UV Light Emitting Diodes （LED） combined with tricolor phosphors.     

Flux and concentration effect on Eu^3＋ doped Gd2（MoO4）3 phosphor

A novel red emitting phosphor Gd2（MoO4）3：Eu^3＋ was prepared by solid reaction, using Gd2O3, Eu2O3 and WO3 as starting matedals and NH4F as flux. The effects of flux content and Eu^3＋ concentration on the crystal structure, morphology and luminescent properties were investigated using XRD, SEM and fluorescent spectrum measurement. The XRD patterns showed that the resultants had the monoclinic structure. With the increase in flux amount, their crystallization significantly improved. The SEM images indicated that the mean size of the phosphor particles was around 2 μm, and agglomeration of the phosphor particles appeared while introducing higher flux amount. The excitation spectra exhibited more intense f-f transitions originating from ground state 7^F0 to upper states 5^L6 and 5^D2 than the charge transfer band. The concentration quenching of Eu^3＋ emission indicated that energy transfer from Eu^3＋ to molybdate host existed even at lower Eu^3＋ concentration.     

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%.     

Luminescence and Preparation of LED Phosphor Ca8Mg （ SiO4）4Cl2 ： Eu^2＋

Calcium magnesium chlorosilicate doped by europium, Ca8Mg（SiO4）4Cl2： Eu^2＋, 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： Eu^2＋ 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 Eu^2 ＋ is 2%. The wavelength of emission and excitation of the phosphor with various Eu^2 ＋ 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.     

A green-yellow emitting β-SreSiO4：Eu^2＋ phosphor for near ultraviolet chip white-light-emitting diode

Sr2SiO4：xEu^2＋ phosphors were synthesized through the solid-state reaction technique. The crystal phase of Sr2SiO4：xEu^2＋ phosphor manipulated by Eu^2＋ concentration was studied. The phase transited from β to α＇ in Sr2SiO4：xEu^2＋ phosphor with increasing europium concentration. The single β phase was formed as x≤005 and changed α＇ phase when x〉0.01. The emission spectrum of the β-Sr2SiO4：Eu^2＋ phosphor consisted of a green-yellow broadband peaking at around 540 nm and a blue band at 470 nm under near ultraviolet excitation. The white LEDs by combining near ultraviolet chips with β-Sr2SiO4：Eu^2＋ phosphors were fabricated. The luminous efficiency （15.7lm/W） was higher than α＇-Sr2SiO4：Eu^2＋ phosphor white LED.     

Luminescent Properties of Green Phosphor Ca8Mg（SiO4 ）4 Cl2：EU^2＋ , DY^3＋ for LED Applications

The new phosphor calcium magnesium chlorosilicate, codoped with Eu^2＋ and Dy^3＋, was synthesized with the help of the high temperature solid state reaction in reducing atmosphere. The excitation and emission spectra were very similar to that of Ca8Mg（SiO4）4Cl2 ：Eu^2＋, and the Dy^3＋ concentration influenced the emission intensity of this phosphor. The intensity of Eu^2＋ and Dy^3＋ codoped CMSC was stronger than that of Eu^2＋ singly doped CMSC. The emission spectrum of the Dy^3＋ ion overlapped the absorption band of the Eu^2＋ ion, indicating that an energy transfer from Dy^3＋ to Eu^2＋ took place in CMSC：Eu^2＋, Dy^3＋ phosphor. The mechanism of the energy transfer from Dy^3＋ tO Eu^2＋, in this phosphor, might be resonant energy transfer.     

SrAl2O4∶Eu2+,Dy3+磷光粉低成本制备工艺及发光性能研究

以工业铝酸钠溶液制备的氢氧化铝为铝基原料,采用高温固相反应法合成了SrAl2O4∶Eu2+,Dy3+磷光粉,考察了稀土掺杂量、烧结温度及硼酸加入量对其发光性能、激发光谱及发射光谱的影响,并通过XRD谱及余辉衰减曲线对最佳工艺条件下制备的样品进行表征。结果表明,当稀土掺杂量x(Eu)=3%、x(Dy)=3%,烧结温度为1 300℃,烧结时间为4h,硼酸加入量w(H3BO3)=9%时,所制备磷光粉样品仍保持SrAl2O4的晶体结构,其发光性能最好,发光强度最大,主激发波长在360nm左右,主发射波长在510nm左右;余辉为黄绿色,衰减时间长。     

Luminescent properties of Ba3Gd（BO3）3：Eu^3＋ phosphor for white LED applications

Luminescent material Ba3Gd(BO3)3 doped with Eu3+ ion was prepared by high temperature solid-state method. The preparing conditions, luminescent properties, and particle morphology of Ba3Gd(BO3)3:Eu3 + phosphor were studied with X-ray diffraction (XRD), fluorescence spectroscopy, and scanning electron microscopy (SEM). The results obtained by XRD showed that pure phase of Ba3Gd(BO3)3 was obtained at 1000℃. Images from SEM displayed that the particles of Ba3Gd(BO3)3:Eu3+ phosphor had a spherical shape with an average diameter of about 200-400 nm. The luminescence spectra showed that Ba3Gd(BO3)3:Eu3+ phosphor was effectively excited by the near ultraviolet (UV) light (396 nm) and blue light (466 nm). The main emission peaks of Ba3Gd(BO3)3:Eu3+ phosphor were assigned to the supersensitive transition 5D0-7F2 (611 and 616 nm) of Eu3+ ion when samples were excited at 255 and 396 nm, respectively, and the luminescent intensity of Ba3Gd(BO3)3:Eu3+ at 611 and 616 nm reached to the maximum when the doped content of Eu3+ ion was 10mol.%. Therefore, this phosphor could be a promising red component for possible applications in the field of white LED.     

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   

Effect of gadolinium incorporation on optical characteristics of YNbO_4：Eu~（3＋） phosphors for lamp applications

Eu3+-doped (Y,Gd)NbO4 phosphor was synthesized by solid-state reaction for possible application in cold cathode fluorescent lamps. A broad absorption band with peak maximum at 272 nm was observed which was due to the charge transfer between Eu3+ ions and neighboring oxygen anions. A deep red emission at the peak wavelength of 612 nm was observed which could be attributed to the 5D0→7F2 transition in Eu3+ ions. The highest luminance for Y1-x-yGdyNbO4:Eux3+ under 254 nm excitation was achieved at Eu3+ concentration of 18 mol.% (x=0.18) and Gd3+ concentration of 8.2 mol.% (y=0.082). The luminance of Y0.738Gd0.082NbO4:Eu3+0.18 was higher than that of a typical commercial phosphor Y2O3:Eu3+ and the CIE chromaticity coordinate was (0.6490, 0.3506), which was deeper than that of Y2O3:Eu3+. The particle size of the synthesized phosphors was controlled by the NaCl flux and particle size as high as 8 μm with uniform size distribution of particles was obtained.     

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.     

Vacuum ultraviolet excited photoluminescence properties of Gd2O2CO3:Eu3+ phosphor

The Gd2O2CO3:Eu3 with type-II structure phosphor was successfully synthesized via flux method at 400℃ and their photoluminescence properties in vacuum ultraviolet (VUV) region were examined. The broad and strong excitation bands in the range of 153-205 nm owing to the CO32- host absorption and charge transfer (CT) of Gd3 -O2- were observed for Gd2O2CO3:Eu3 . Under 172 nm excitation, Gd2O2CO3:Eu3 exhibited strong red emission with good color purity, indicating Eu3 ions located at low symmetry sites and the chromaticity coordination of luminescence for Gd2O2CO3:Eu3 was (x=0.652, y=0.345). The photoluminescence quenching concentration of Eu3 excited by 172 nm for Gd2O2CO3:Eu3 was about 5%. Gd2O2CO3:Eu3 would be a potential VUV-excited red phosphor applied in mercury-free fluorescent lamps.     

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.