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.     

Enhancement of photoluminescence of Ba2SiO4：Eu^2＋ by co-doping of La^3＋ or Y^3＋

Green light-emitting Ba2SiO4:Eu2+ phosphors co-doped with La or Y were synthesized by conventional solid-state reaction technique in reductive atmosphere (a mixture of 5% H2 and 95% N2). The results showed that the co-doping of La and Y could greatly enhance the fluorescence intensity of Ba2SiO4:Eu2+ phosphors. The optimum doping concentration expressed by the x value in (Ba0.985-1.5xREx)2SiO4: 0.03Eu2+ (RE=La or Y) was determined to be of 0.05. The excitation and emission peaks of all as-synthesized phosphors were wide bands. The excitation bands ranged from 250 to 400 nm, which matched well with the wavelength of near ultraviolet white light-emitting diodes (LED) chip and could be used as a potential candidate for the fabrication of white LED. The emission bands from 450 to 550 nm were typical 5d-4f transition emission of Eu2+ and displayed un-symmetry profiles because of the two substitution sites of Ba2+ with Eu2+.     

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.     

Cooperative energy transfer in Eu3+,Yb3+ codoped Y2O3 phosphor

Under 980 nm laser excitation,red emission(5D0-7FJ(J=0,1,2)) of Eu3+ was observed in cubic Y2O3 codoped with Eu3+ and Yb3+.The dependence of the upconverted emission on doping concentration and laser power was studied.Yb3+ emission around 1000 nm(2F5/2-2F7/2) was reported upon excitation of Eu3+ ions.The decay curves of 5DJ(J=0,2) emission of Eu3+ under excitation of 266 nm pulse laser were examined to investigate the Eu3+→Yb3+ energy transfer process.Cooperative energy transfer process was discussed as the possible mechanism for the visible up-conversion luminescence of Eu3+ and near-infrared down-conversion emission of Yb3+.     

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.     

Ba1-xSrxMgSiO4:Eu2+,Mn2+: A novel tunable single-matrix tricolor phosphor for W-LED

The Ba1-xSrxMgSiO4:Eu2+,Mn2+ phosphors were prepared by solid-state reaction. Their photoluminescence properties were inves-tigated with fluorescence spectrum and CIE chromaticity. The emission color of Eu2+ in Ba0.98-xSrxMgSiO4:0.02Eu2+ could be tuned from green to blue by adjusting the content of Sr2+. The blue emission of Eu2+ overlapped well with the excitation spectra of Mn2+, leading to an ef-ficient energy transfer from Eu2+ to Mn2+ in Ba0.98-xSrxMg1-ySiO4:0.02Eu2+,yMn2+. Ba0.93Sr0.03Mg1-ySiO4:0.02Eu2+,yMn2+ could emit three ef-ficient broad bands at 440, 530 and 640 nm. The emission color of Ba0.93Sr0.03Mg1-ySiO4:0.02Eu2+,yMn2+ could be tuned from greenish blue to yellowish white by increasing the content of Mn2+ from 0 to 0.1. By changing the content of Sr2+/Mn2+, white-light with different hues could be conveniently obtained in the Ba1-xSrxMgSiO4:Eu2+,Mn2+ phosphors. The results showed that Ba1-xSrxMgSiO4:Eu2+,Mn2+ is a promising single-phased tricolor phosphor in the fabrication of W-LED.     

Luminescence Properties of Eu~(2 ) and Mn~(2 ) Co-Doped Ca_8Mg(SiO_4)_4Cl_2

The green phosphor for white LED, Ca8Mg(SiO4)4Cl2∶Eu2+, Mn2+, was synthesized by high temperature solid state reaction under reducing atmosphere. During the process of the phosphor prepared, the excess CaCl2 can improve the intensity of emission. The experimental results indicate that there is an effective energy transfer from Eu2+ to Mn2+in Ca8Mg(SiO4)4Cl2 host. This kind of energy transfer may be due to resonance transfer, and this energy transfer is limited.     

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.     

A potential single-phased white-emitting LiBaBO3:Ce3+,Eu2+ phosphor for white LEDs

Ce3+/Eu2+ co-doped LiBaBO3 phosphor was synthesized by high temperature solid-state reaction method, and its luminescent character- istics were investigated. The hues of the LiBaBO3:Ce3+, Eu2+ phosphor varies from blue to white and eventually to yellow-green by properly tuning the Ce3+/Eu2+ ratio. Under UV excitation, white light was generated by coupling blue and yellow-green emission bands attributed to Ce3+ and Eu2+ emissions, respectively. The luminous efficacy of LiBaBO3:1%Ce3+, 2%Eu2+ calculated from ...     

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.     

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...     

Preparation,structure and luminescence properties of deep red phosphors SrSiN2:Eu2+

This paper reported a novel synthetic route to Eu2+ doped SrSiN2 deep red phosphors for white light-emitting diodes. A series of single-phased and high-efficiency Sr Si N2:Eu2+ red phosphors were synthesized based on this method. Their structure, morphology, luminescence, quantum efficiency(QE) and thermal quenching properties were investigated and compared with those of Sr Si N2: Eu2+ prepared by the conventional route. It was found that the addition of a small amount of Si3N4 could promote the formation of Sr Si N2 from Sr2Si5N8 phase. A highly uniform rod-shaped morphology was obtained based on this method. The X-ray powder diffraction and the Rietveld refinement analysis identified the preferential crystalline orientation growth. Under the blue light excitation, Eu2+ doped Sr Si N2 phosphors showed excellent optical properties. Compared with those prepared by the conventional approaches, the external QE of Sr Si N2:Eu2+ phosphor was greatly improved, allowing it a promising phosphor for white LEDs.     

Synthesis and Luminescence Properties of Ba2 MgSi2 O7 :Eu2+ under UV Excitation

Eu2 activated pyrosilicate phosphor were prepared under a reducing atmosphere by solid-state reaction.The crystal structure of Ba2 MgSi2 O7: Eu2 was analyzed by XRD method.The excitation spectrum of Ba2MgSi2 O7; Eu2 is composed of two broad bands centered at about 310 nm and 395 nm respectively.In the emission spectra, the peak wavelength is at about 507 nm under 380 nm UV excitation.It was found that the introduction of Zn2 into Ba2MgSi2O7: Eu2 Can effectively increase its emission intensity without changing the position of emission peak.And the Eu2 and Ce3 codoped pyrosilicate phosphor is the efficient bluish green phosphor under the excitation of long UV light and its emission intensity is stronger than Eu2 doped pyrosilicate phosphor.     

掺杂Eu3+离子的YPO4的合成及其发光特性

用BPO4和稀土氧化物为原料，采用固相反应法合成了掺杂Eu^3 离子的YPO4，并用X射线粉末衍射对其结构进行了表征，X射线粉末衍射实验结果表明，YPO4属四方晶系，晶胞参数α=0.6894nm,c=0.6020nm，属I41/αmd(No.141)空间群，测定了其激发光谱和发射光谱，探讨了掺杂Eu^3 离子的YPO4的发光特性。     

Synthesis of Long Afterglow Phosphors MAl2O4:Eu2+, Dy3+(M=Ca, Sr, Ba) by Microemulsion Method and Their Luminescent Properties

Long afterglow phosphors MAl2O4:Eu2 , Dy3 (M=Ca, Sr, Ba) were synthesized by microemulsion method, and their crystal structure and luminescent properties were compared and investigated. XRD patterns of samples indicate that phosphors CaAl2O4:Eu2 , Dy3 and SrAl2O4:Eu2 , Dy3 are with monoclinic crystal structure and phosphor BaAl2O4:Eu2 , Dy3 is with hexagonal crystal structure. The wide range of excitation spectrum of phosphors MAl2O4:Eu2 , Dy3 (M=Ca,Sr,Ba) indicates that the luminescent materials can be excited by light from ultraviolet ray to visible light and the maximum emission wavelength of phosphors MAl2O4:Eu2 , Dy3 (M=Ca, Sr, Ba) is found mainly at λem of 440 nm (M=Ca), 520 nm (M=Sr) and 496 nm (M=Ba) respectively, the corresponding colors of emission light are blue, green and cyna-green respectively. The afterglow decay tendency of phosphors can be summarized as three processes: initial rapid decay, intermediate transitional decay and very long slow decay. Afterglow decay curves coincide with formula I=At-n, and the sequence of afterglow intensity and time is Sr＞Ca＞Ba.     

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.     

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.     

Synthesis of Long Afterglow Phosphor CaAl2Si2O8:Eu2+, Dy3+ via Sol-Gel Technique and Its Optical Properties

The long afterglow phosphor CaAl2Si2O8:Eu2 , Dy3 was prepared by a sol-gel method. The sol-gel process and the structure of the phosphor were investigated by means of X-ray diffraction analysis (XRD). It is found that the single anorthite phase formed at about 1000 ℃, which is 300 ℃ lower than that required for the conventional solid state reaction. The obtained phosphor powders are easier to grind than those of solid state method and the partical size of phosphor has a relative narrow distribution of 200 to 500 nm. The photoluminescence and afterglow properties of the phosphor were also characterized. An obvious blue shift occurs in the excitation and emission spectra of phosphors obtained by sol-gel and solid state reaction methods. The change of the fluorescence spectra can be attributed to the sharp decrease of the crystalline grain size of the phosphor resulted from the sol-gel technique.     

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.     

Preparation and luminescence properties of the red-emitting phosphor（Sr1-xCax）2Si5N8：Eu^2＋ with different Sr/Ca ratios

A series of Eu2+-doped ternary nitride phosphors, with a formula of (Sr1-xCax)2Si5N8: Eu2+, were synthesized by high-temperature solid-state method. The structure and luminescence properties were characterized, indicating the potential application as a red phosphor in the phosphor-converted white light-emitting diodes. The X-ray diffraction patterns showed that the Sr2Si5N8 and Ca2Si5N8 phases were generated at each end of (Sr1-xCax)2Si5N8: Eu2+ and coexisted in the range of 0.5≤x≤0.75. The emission spectra showed broad emission bands originating from the 4f65d1→4f7 transition of Eu2+ ions. The emission peak changed with the variations in Ca2+ concentration.