Ca(NO3)2·4H2O, Eu(NO3)3 and H2C2O4·2H2O were adopted to synthesize CaO: Eu3+ with the chemical co-precipitation method, and the effects of the calcination temperature and Eu3+ doping concentration on the pho...Ca(NO3)2·4H2O, Eu(NO3)3 and H2C2O4·2H2O were adopted to synthesize CaO: Eu3+ with the chemical co-precipitation method, and the effects of the calcination temperature and Eu3+ doping concentration on the phosphor structure and its luminescent properties were investigated by TG-SDTA, XRD, and PL-PLE. The results confirm that the Eu3+ ions as luminescent centers substi-tutes Ca2+ sites without changing the crystal structure of cubic CaO. The optimum calcination tem-perature and the optimum concentration of Eu3+ are 1 100 ℃ and 1 mol%, respectively, under which the best crystallinity and highest PL intensity appeared. The maximum emission wavelength is 592 nm (5D0→7F1) which is excited by xenon lamp with the wavelength of 200-280 nm, indicating that the Eu3+ ion mainly locates in the symmetric position (Oh) in the crystal lattice of CaO.展开更多
Sol-gel method was utilized to synthesize two different series of red silicate phosphors:MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3:Eu2+, Dy3+, ...Sol-gel method was utilized to synthesize two different series of red silicate phosphors:MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3:Eu2+, Dy3+, Mn2+. TGA curves of the gel precursor for two series depicted that the loss of residual organic groups and NO3 groups occurs below 450 ℃. According to the XRD patterns, the major diffraction peaks of the MgSiO3 and Mg2SiO4 series are consistent with a proto-enstatite structure (JCPDS No.11-0273) and a forsterite structure (JCPDS No.85-1364) respectively. With the excitation at 415 nm, the red emission band of Mn2+ ions is peaked at 661 nm for MgSiO3:1%(atom fraction) Mn2+ or 644 nm for Mg2SiO4:1%(atom fraction) Mn2+. Compared with Mg2SiO4:Mn2+ samples, MgSiO3:Mn2+ samples exhibit higher luminescence intensity and higher quenching concentration. In addition, the two series co-doped with Eu2+, Dy3+, Mn2+ were also prepared. Photo-luminescence and afterglow properties of the two co-doped series were analyzed, which show that MgSiO3:Eu2+, Dy3+, Mn2+ is more suitable for a red long-lasting phosphor.展开更多
A complete solid solutions with monophasic zircon-type structure of vanadates of formula GdxBi0.95-xVO4:0.05Eu3+(x = 0–0.95) are synthesized by combined method of co-precipitation and hydrothermal synthesis. Their mi...A complete solid solutions with monophasic zircon-type structure of vanadates of formula GdxBi0.95-xVO4:0.05Eu3+(x = 0–0.95) are synthesized by combined method of co-precipitation and hydrothermal synthesis. Their microstructures and morphologies are characterized by X-ray powder diffraction and transmission electronic microscope, and the results show that each of all the samples has a monophasic zircon-type structure. The absorption spectrum of the prepared phosphor shows a blue-shift of the fundamental absorption band edge with increasing the gadolinium content. Under UV-light and visible-light excitation, all the prepared phosphors show the typical luminescence properties of Eu3+in the zircon-type structure. The emission intensity of GdxBi0.95-xVO4:0.05Eu3+(x = 0.55) is strongest in all samples under UV-light and visible-light excitations. Finally, the mechanisms of luminescence of Eu3+in the GdxBi0.95-xVO4:0.05Eu3+(x = 0–0.95)solid solutions are analyzed and discussed.展开更多
A series of (SrNa)2-xEux(MoO4)3 red phosphors have been synthesized by using the sol-gel method. X-ray diffraction, used to characterize the crystallization process of the phosphor precursors, indicates that the (SrNa...A series of (SrNa)2-xEux(MoO4)3 red phosphors have been synthesized by using the sol-gel method. X-ray diffraction, used to characterize the crystallization process of the phosphor precursors, indicates that the (SrNa)2-xEux(MoO4)3 phosphors had an SrMoO4 structure. The properties of these resulting phosphors have also been characterized by using photoluminescence (PL) spectra. The PL results indicate that all of the (SrNa)2-xEux(MoO4)3 phosphors exhibit intense red emissions under 275, 395, and 465-nm excitation. The two strongest lines at 395 and 465 nm in the excitation spectra of these phosphors match well with the two popular emissions from near-UV and blue GaN-based light-emitting diodes. Some process parameters for Eu3+ concentration, (C6H8O7)·H2O concentration, and solution pH value were also investigated. For (SrNa)2-xEux(MoO4)3 phosphors, there are two maximum emission intensities appearing with x = 0.6 and x = 1.4, respectively. When the molar ratio of citric acid is equal to that of metal cations and the solution pH is almost 4, (SrNa)2-xEux(MoO4)3 shows the strongest emission intensity compared to those under other conditions.展开更多
The S-scheme heterojunctions can effectively separate photogenerated electrons and holes,retain their high redox capacity,and provide great prospects for enhancing the photocatalytic activity of the composites in diff...The S-scheme heterojunctions can effectively separate photogenerated electrons and holes,retain their high redox capacity,and provide great prospects for enhancing the photocatalytic activity of the composites in different fields.Herein,S-scheme heterojunction photocatalytic materials were rationally designed and prepared by a simple hydrothermal method between narrow-bandgap red phosphorus(HRP)and wide-bandgap BaTiO_(3)(BTO)photocatalysts.Owing to the effective charge separation and redox ability from the S-scheme mechanism and oxygen vacancies,BTO/HRP exhibited good photoelectrochemical and photocatalytic degradation ability.Systematic photoreaction tests demonstrated that BTO/HRP had high practicality in the removal of pollutants from wastewater;its photodegradation rate of Rhodamine B reached 3.029×10^(−1) min^(−1) in 12 min;and it could inactivate 1.8×10^(9) CFU/mL of Escherichia.coli in 1 h,with an antibacterial rate of 99.8%.This paper provided a promising photocatalyst for pollutant removal and a new strategy for the fabrication of efficient RP-based photocatalytic materials.展开更多
Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural ...Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural modification.The correlations among structural evolution,crystal-field environment,and luminescence properties were elucidated.Replacing Sr^(2+)with Gd^(3+)in(Sr,Gd)LiAl_(3)N_(4):Eu^(2+)leads to the enhanced crystal field splitting,larger Stokes shift,and increased structural polyhedron distortion differences,consequently resulting in spectral red-shift and broadening.For further spectral tuning,Mg,with lower electronegativity,was also introduced to modify the local crystal structure,consequently resulting in a further red-shift towards 675 nm and enhanced photoluminescence intensity in(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+).What’s more,w-LEDs were fabricated by using blue LED chip,blue,green,red and deep red((Sr,Gd)Li(Al,Mg)_(3)N_(4):Eu^(2+))phosphors whose color rendering index were Ra 96.0 and R997.7.All above results demonstrate that the partial replacements of Sr^(2+)by Gd^(3+)and Al^(3+)by Mg^(2+)are effective methods for spectral modulation and(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)phosphors are suitable for highquality full-spectrum WLEDs.展开更多
A series of non-rare earth Mn^(4+)-activated strontium aluminate phosphors Sr_(4)Al_(14)O_(25):Mn^(4+)co-doped with Sc^(3+)ions were successfully synthesized by a high-temperature solid-state reaction method.XRD resul...A series of non-rare earth Mn^(4+)-activated strontium aluminate phosphors Sr_(4)Al_(14)O_(25):Mn^(4+)co-doped with Sc^(3+)ions were successfully synthesized by a high-temperature solid-state reaction method.XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc34 ions.Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light,and a deep red emission centered at 652 nm with a narrow full width at half maximum(FWHM)can be obtained,which is attributed to the transition^(2)E→^(4)A_(2)of Mn^(4+)ions.In addition,the crystal field strength parameter(Dq)and Racah parameters(B,C)and energies of states were calculated based on experimental data.Moreover,the luminous intensity of Sr_(4)Al_(14-x)SCxO_(25):Mn^(4+)is enhanced and increased by 60%compared with Mn^(4+)single incorporated sample at x=0.06.A phenomenon of redshift is observed in the excitation spectrum and discussed systematically.Finally,the mechanism of the positive effects with Sc^(3+)ions incorporated into lattice is discussed in detail.All the results suggest that the Sr_(4)Al_(13.94)Sc_(0.06)O_(25):Mn^(4+)phosphor will become one of the great candidates for backlight of LCD.展开更多
A series of(Y_(1-y), Gdy)_(0.95-x)(P_y, V_(1-y))O_4 :0.05Eu^(3+), xBi^(3+)+phosphors have been successfully prepared by a subsection method. The crystal structure, surface morphology and luminescence properties were i...A series of(Y_(1-y), Gdy)_(0.95-x)(P_y, V_(1-y))O_4 :0.05Eu^(3+), xBi^(3+)+phosphors have been successfully prepared by a subsection method. The crystal structure, surface morphology and luminescence properties were investigated. It was found that the sintered samples crystallized in a tetragonal crystal system with space group I_(41)/amd(a = b = 0.7119 nm, c = 0.6290 nm). The products presented rod-like morphology with length of 100-150 nm and width of 50-100 nm. A maximum peak at 619 nm(~5D_0 →~7F_2) was observed in emission spectrum of the phosphors. It was also found that co-doping of Bi^(3+)+, P5+and Gd^(3+)ions into YVO_4:Eu^(3+)can not only made the right edge of the excitation band shift to the long-wavelength region, but also increased the emission intensity at 619 nm sharply and decreased the lifetime of fluorescence decay. These results may expand the application scope of the phosphors.展开更多
Red phosphor K_2LiAlF_6:Mn^(4+) has been synthesized by a cation-exchange method in HF solution. To optimize their optical properties, phosphors were synthesized using different reaction conditions. The K_2LiAlF_6:0.5...Red phosphor K_2LiAlF_6:Mn^(4+) has been synthesized by a cation-exchange method in HF solution. To optimize their optical properties, phosphors were synthesized using different reaction conditions. The K_2LiAlF_6:0.5%Mn^(4+) synthesized at 20℃ for4 h shows the highest luminescence intensity. The temperature-dependent emission intensity of the phosphor was investigated,and it was found to exhibit good thermal stability, making it a promising red phosphor candidate for warm WLEDs.展开更多
A series of new oxyapatite red phosphors Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O doped with different concentrations of Eu^(3+)were successfully synthesized by high temperature solid state method.The X-ray diffraction(XR...A series of new oxyapatite red phosphors Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O doped with different concentrations of Eu^(3+)were successfully synthesized by high temperature solid state method.The X-ray diffraction(XRD)Rietveld refinement results show that the structure of the phosphor belongs to space group P6_(3)/m and Eu^(3+)ion replaces Y^(3+)ion.The emission spectrum consists of the characteristic emission peaks corresponding to Eu^(3+)under the excitation of 274 nm and the dominant emission peak is at 614 nm(^(5)D_(0)→^(7)F_(2) of Eu^(3+)).The concentration quenching effect occurs and the optimized Eu^(3+)concentration is 4.0 mol%.The energy level diagram for luminous mechanism is also given and the non-radiative energy transfer mechanism between Eu^(3+)is mainly exchange interaction.The CIE coordinate is close to the ideal red light and the color purity is higher than 99.79%.Moreover,the phosphor exhibits moderate thermal stability because the photoluminescence intensity at 423 K is still maintained at higher than 78.97%of that at room temperature.The internal quantum efficiency of Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O:4.0 mol%Eu^(3+)phosphor is 58.2%.A red light emitting diode(LED)device based on it can emit bright red light.The CCT values of the device are basically unchanged when driven by various bias current.The results show that Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O:Eu^(3+)is a new type of oxyapatite red fluorescent material with good comprehensive performances.展开更多
The novel nitride-based luminescent materials have received much attention since the end of the last century. In this paper, the commercial Eu2+-activated nitride red phosphors, Sr1.95 Si5 N8 :Eu0.05, Sr1.85 Si5 N8 :E...The novel nitride-based luminescent materials have received much attention since the end of the last century. In this paper, the commercial Eu2+-activated nitride red phosphors, Sr1.95 Si5 N8 :Eu0.05, Sr1.85 Si5 N8 :Eu0.15 and Ca0.99 AlSiN3 :Eu0.01 phosphors were annealed at different temperatures(beyond 300 oC) to investigate the dependence of their luminescence performance and structure variability on the temperature. By photoluminescence spectra, X-ray diffraction(XRD) and thermogravimetry-differential scanning calorimetry(TG-DSC) analysis, the high temperature stability of the hosts and activator of the three samples were disclosed. With the annealing temperature increasing, the activator Eu2+ions were firstly oxidized and then host in Sr1.95 Si5 N8 :Eu0.05 and Sr1.85 Si5 N8 :Eu0.15, but for Ca0.99 AlSiN3 :Eu0.01, only the oxidation of the host could be observed, which would lead to the luminescence degradation and even failure of these phosphors. The activator Eu2+ions were much more stable in CaAlSiN3 :Eu than Sr2 Si5 N8 :Eu due to their crystal surroundings, and its concentration also influenced the temperature stability of Sr2 Si5 N8 :Eu.展开更多
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 (39...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%.展开更多
A series of red phosphors Ca10Li (PO4)7:Eu3+ were synthesized by high temperature solid-state reaction method. Their luminescence properties were characterized by means of photoluminescence excitation and emission spe...A series of red phosphors Ca10Li (PO4)7:Eu3+ were synthesized by high temperature solid-state reaction method. Their luminescence properties were characterized by means of photoluminescence excitation and emission spectra,CIE chromaticity and quantum efficiency. Results indicated that the phosphors could be effectively excited by the near ultraviolet (NUV) light (393 nm). The main emission peaks of the phosphor were ascribed to the transition 5D0-7F2 (613 and 617 nm) of Eu3+ ion when samples were excited by 393 nm. The CIE chromaticity (x,y) of Ca9.9Li (PO4)7:0.10Eu3+ was x=0.638,y=0.361 and the quantum efficiency of this phosphor was 75% excited by 393 nm. Therefore,this phosphor could be a promising red component for the applications in white LEDs.展开更多
The Bi3+ doped molybdate-based red-emitting phosphors, LiEu1-xBix(MoO4)2, were successfully synthesized with a sol-gel method. The prepared LiEu1-xBix(MoO4)2 phosphors exhibited pure and intense red emission at 613 nm...The Bi3+ doped molybdate-based red-emitting phosphors, LiEu1-xBix(MoO4)2, were successfully synthesized with a sol-gel method. The prepared LiEu1-xBix(MoO4)2 phosphors exhibited pure and intense red emission at 613 nm under the excitation of near-UV 394 nm. It was discussed in detail that the influence of the synthesis conditions such as the doping concentration of Bi3+, the dose of citric acid, pH of the precursor solution and the sintering temperature on the emission intensity of the phosphors. According to the results, the optimal condition was obtained: the doping concentration of Bi3+ was 15 mol.%, molar ratio of citric acid to metal ions was 1.5:1, pH of the precursor solution was 1.0 and the sintering temperature was 800 ?C. The X-ray diffraction (XRD) patterns of the LiEu0.85Bi0.15(MoO4)2 phosphor prepared under the optimal condition indicated that the phosphor was single phase with tetragonal scheelite structure. The Commission Internationale de l'E-clairage (CIE) chromaticity coordinates of LiEu0.85Bi0.15(MoO4)2 were (x=0.655, y=0.345), which were closer to the national television stan-dard committee (NTSC) standard values (x=0.670, y=0.330) than that of a commercial red phosphor of Y2O2S:Eu3+(x=0.630, y=0.350). This LiEu0.85Bi0.15(MoO4)2 red phosphor is a promising candidate for the fabrication of white light-emitting diode (W-LED) with near-UV chips.展开更多
Eu-activated CaMoO4 phosphors were co-precipitated in an aqueous solution, and NH3·H2O, NH4HCO3 and (NH2)2CO as pre-cipitating aid agents were compared based on the morphology and particle size distribution of th...Eu-activated CaMoO4 phosphors were co-precipitated in an aqueous solution, and NH3·H2O, NH4HCO3 and (NH2)2CO as pre-cipitating aid agents were compared based on the morphology and particle size distribution of the phosphor samples. Sm3+ as sensitizer ion was investigated on the luminescence of CaMoO4:Eu, and it could strengthen the 406 nm absorption of this phosphor. At last, the scheelite CaMoO4:Eu and wolframite ZnMoO4:Eu were selected to compare their host absorption. The result showed that the scheelite molybdate host exhibited stronger UV absorption than wolframite one.展开更多
A series of novel Sm3+-doped LiY(MoO4)2 red phosphors under the UV excitation were synthesized by solid state reaction at 800 oC for 7 h. The data measured by X-ray diffraction(XRD) indicated that the samples were all...A series of novel Sm3+-doped LiY(MoO4)2 red phosphors under the UV excitation were synthesized by solid state reaction at 800 oC for 7 h. The data measured by X-ray diffraction(XRD) indicated that the samples were all pure phases of LiY(MoO4)2. Their excitation spectra had a broad band ranging from 250 to 350 nm and several sharp peaks. The centers of the peaks were located at about 365 nm(6H5/2→4D3/2), 378 nm(6H5/2→6P7/2), 406 nm(6H5/2→4F7/2), 420 nm(6H5/2→6P5/2), 442 nm(6H5/2→4G9/2), 471 nm(6H5/2→4I13/2) and 482 nm(6H5/2→4I9/2), respectively. The strongest emission was excited by 406 nm, and the main emissions were located at 568 nm(4G5/2→6H5/2), 610 nm(4G5/2→6H7/2), 649 nm(4G5/2→6H9/2) and 710 nm(4G5/2→6H11/2). Photoluminescence properties were determined for various concentrations of Sm3+-doped LiY(MoO4)2 host, and the luminescence intensity had the best value when x=0.02 in LiY1–x(MoO4)2:xSm3+.展开更多
CaTiO3:Eu3+ red phosphors were prepared using H3BO3 assisted solid state synthesis.The structure and morphology of the obtained sample were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).An...CaTiO3:Eu3+ red phosphors were prepared using H3BO3 assisted solid state synthesis.The structure and morphology of the obtained sample were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).And the luminescence property was measured using photoluminescence excitation (PLE) and photoluminescence (PL) spectra,respectively.In the excitation spectra,main excitation peaks of the prepared samples were centered at 397 and 465 nm,revealing that these phosphors could be excited by commercial GaNand InGaN-typed light emitting diodes (LEDs).Dominant emission peaks of the phosphors were located at 616 nm,owing to the transition of 5D0→7F2 of Eu3+.In the optimum condition,CaTiO3:3%Eu3+ phosphor was obtained at a sintering temperature of 1200 ℃ in air with a content of 20 mol.% H3BO3 addition.When excited by 397 nm irradiation,the PL intensity of as-prepared red phosphor was 2.2 times higher than that of samples obtained by traditional solid state synthesis,while the PL intensity was 3 times higher than that excited by 465 nm irradiation.The added H3BO3 improved the crystallinity,and increased the color purity,implying the potential to be a promising red phosphor in white light emitting diodes (WLEDs).展开更多
A series of novel red phosphors LiEu1-xYx(WO4)0.5(MoO4)1.5 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8) were synthesized by conventional solid state reaction method with the starting materials: WO3, MoO3, Eu2O3, Li2CO3 an...A series of novel red phosphors LiEu1-xYx(WO4)0.5(MoO4)1.5 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8) were synthesized by conventional solid state reaction method with the starting materials: WO3, MoO3, Eu2O3, Li2CO3 and Y2O3. The spectrum and the crystal structure of the phosphors were characterized by F-4500 and XRD respectively. Meanwhile the effects of flux and Y3+ concentration on the crystal structure and luminescent properties of the phosphors were investigated. The results showed that the optimal content of flux (WAlF3/WH3BO3=1/1) was 1 wt% and the optimal doping concentration of Y3+ was 0.5 mol. The emission spectrum showed the most intense peak was located at 615 nm, which corresponds to the 5D0→7F2 transition of Eu3+ and that Eu3+ occupied the lattice site of noncentrosymmetric environment in the scheelite phases. The excitation spectrum displayed that these phosphors could be effectively excited by ultraviolet (UV) (396 nm) and blue (466 nm) light, nicely in correspondence with the widely ap- plied output wavelengths of ultraviolet or blue LED chips. The influence of flux on the luminescent properties of LiEu0.5Y0.5(WO4)0.5(MoO4)1.5 phosphor was analyzed. The XRD spectra indicated that the flux could help to crystallize the phosphor, and no other phases were formed except the tetragonal. When adding flux, the relative intensity of LiEu0.5Y0.5(WO4)0.5(MoO4)1.5 became much stronger and the average particle size of the phosphor decreased.展开更多
Red phosphor (Y, Gd)BO3:Eu3+ with grain shape, small size, non-agglomerate, high crystallinity and good photoluminescence (PL) intensity was prepared by a complex method that the precursor of the phosphor was prepared...Red phosphor (Y, Gd)BO3:Eu3+ with grain shape, small size, non-agglomerate, high crystallinity and good photoluminescence (PL) intensity was prepared by a complex method that the precursor of the phosphor was prepared by co-precipitation method and the phosphor was prepared by combustion method. The SEM photos and the photoluminescence spectrum excited under VUV show that the morphology and luminescent properties of this phosphor are satisfied when an appropriate amount of urea was adopted as the combustion agent in the preparation procedure.展开更多
基金Funded by the Science and Technology Bureau of Sichun Province(No.2006J13-059)Education Bureau of Sichun Province (No. 2006A094)
文摘Ca(NO3)2·4H2O, Eu(NO3)3 and H2C2O4·2H2O were adopted to synthesize CaO: Eu3+ with the chemical co-precipitation method, and the effects of the calcination temperature and Eu3+ doping concentration on the phosphor structure and its luminescent properties were investigated by TG-SDTA, XRD, and PL-PLE. The results confirm that the Eu3+ ions as luminescent centers substi-tutes Ca2+ sites without changing the crystal structure of cubic CaO. The optimum calcination tem-perature and the optimum concentration of Eu3+ are 1 100 ℃ and 1 mol%, respectively, under which the best crystallinity and highest PL intensity appeared. The maximum emission wavelength is 592 nm (5D0→7F1) which is excited by xenon lamp with the wavelength of 200-280 nm, indicating that the Eu3+ ion mainly locates in the symmetric position (Oh) in the crystal lattice of CaO.
基金Project is supported by National High Technology Research and Development Program of China (863 Program) (2002 AA 324060)National Natural Science Foundation of China (10404028)
文摘Sol-gel method was utilized to synthesize two different series of red silicate phosphors:MgSiO3 and Mg2SiO4 powder samples doped with Mn2+, conducted the investigation of red long-lasting phosphor: MgSiO3:Eu2+, Dy3+, Mn2+. TGA curves of the gel precursor for two series depicted that the loss of residual organic groups and NO3 groups occurs below 450 ℃. According to the XRD patterns, the major diffraction peaks of the MgSiO3 and Mg2SiO4 series are consistent with a proto-enstatite structure (JCPDS No.11-0273) and a forsterite structure (JCPDS No.85-1364) respectively. With the excitation at 415 nm, the red emission band of Mn2+ ions is peaked at 661 nm for MgSiO3:1%(atom fraction) Mn2+ or 644 nm for Mg2SiO4:1%(atom fraction) Mn2+. Compared with Mg2SiO4:Mn2+ samples, MgSiO3:Mn2+ samples exhibit higher luminescence intensity and higher quenching concentration. In addition, the two series co-doped with Eu2+, Dy3+, Mn2+ were also prepared. Photo-luminescence and afterglow properties of the two co-doped series were analyzed, which show that MgSiO3:Eu2+, Dy3+, Mn2+ is more suitable for a red long-lasting phosphor.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB211708)the National Natural Science Foundation of China(Grant Nos.51272097,61265004,and 61307111)the Natural Science Foundation of Yunnan Province,China(Grant No.2012FD009)
文摘A complete solid solutions with monophasic zircon-type structure of vanadates of formula GdxBi0.95-xVO4:0.05Eu3+(x = 0–0.95) are synthesized by combined method of co-precipitation and hydrothermal synthesis. Their microstructures and morphologies are characterized by X-ray powder diffraction and transmission electronic microscope, and the results show that each of all the samples has a monophasic zircon-type structure. The absorption spectrum of the prepared phosphor shows a blue-shift of the fundamental absorption band edge with increasing the gadolinium content. Under UV-light and visible-light excitation, all the prepared phosphors show the typical luminescence properties of Eu3+in the zircon-type structure. The emission intensity of GdxBi0.95-xVO4:0.05Eu3+(x = 0.55) is strongest in all samples under UV-light and visible-light excitations. Finally, the mechanisms of luminescence of Eu3+in the GdxBi0.95-xVO4:0.05Eu3+(x = 0–0.95)solid solutions are analyzed and discussed.
文摘A series of (SrNa)2-xEux(MoO4)3 red phosphors have been synthesized by using the sol-gel method. X-ray diffraction, used to characterize the crystallization process of the phosphor precursors, indicates that the (SrNa)2-xEux(MoO4)3 phosphors had an SrMoO4 structure. The properties of these resulting phosphors have also been characterized by using photoluminescence (PL) spectra. The PL results indicate that all of the (SrNa)2-xEux(MoO4)3 phosphors exhibit intense red emissions under 275, 395, and 465-nm excitation. The two strongest lines at 395 and 465 nm in the excitation spectra of these phosphors match well with the two popular emissions from near-UV and blue GaN-based light-emitting diodes. Some process parameters for Eu3+ concentration, (C6H8O7)·H2O concentration, and solution pH value were also investigated. For (SrNa)2-xEux(MoO4)3 phosphors, there are two maximum emission intensities appearing with x = 0.6 and x = 1.4, respectively. When the molar ratio of citric acid is equal to that of metal cations and the solution pH is almost 4, (SrNa)2-xEux(MoO4)3 shows the strongest emission intensity compared to those under other conditions.
基金financially supported by the National Natu-ral Science Foundation of China(Nos.52063028,22208275 and 22268003)the Ph.D.Startup Fund of Xinjiang Normal Univer-sity(No.XJNUBS1907)+1 种基金the Xinjiang Normal University Outstanding Young Teachers’Research Initiation Project(No.XJNU202015)the Innovation team for monitoring of emerging contaminants and biomarkers(No.2021D14017).
文摘The S-scheme heterojunctions can effectively separate photogenerated electrons and holes,retain their high redox capacity,and provide great prospects for enhancing the photocatalytic activity of the composites in different fields.Herein,S-scheme heterojunction photocatalytic materials were rationally designed and prepared by a simple hydrothermal method between narrow-bandgap red phosphorus(HRP)and wide-bandgap BaTiO_(3)(BTO)photocatalysts.Owing to the effective charge separation and redox ability from the S-scheme mechanism and oxygen vacancies,BTO/HRP exhibited good photoelectrochemical and photocatalytic degradation ability.Systematic photoreaction tests demonstrated that BTO/HRP had high practicality in the removal of pollutants from wastewater;its photodegradation rate of Rhodamine B reached 3.029×10^(−1) min^(−1) in 12 min;and it could inactivate 1.8×10^(9) CFU/mL of Escherichia.coli in 1 h,with an antibacterial rate of 99.8%.This paper provided a promising photocatalyst for pollutant removal and a new strategy for the fabrication of efficient RP-based photocatalytic materials.
基金supported by the National Key Research and Development Program of China(2021YFB3500402)。
文摘Red phosphor,with longer wavelength,is highly desirable for full-spectrum WLEDs.Targeted deep red phosphors(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)were designed from the initial model of SrLiAl_(3)N_(4):Eu^(2+)by structural modification.The correlations among structural evolution,crystal-field environment,and luminescence properties were elucidated.Replacing Sr^(2+)with Gd^(3+)in(Sr,Gd)LiAl_(3)N_(4):Eu^(2+)leads to the enhanced crystal field splitting,larger Stokes shift,and increased structural polyhedron distortion differences,consequently resulting in spectral red-shift and broadening.For further spectral tuning,Mg,with lower electronegativity,was also introduced to modify the local crystal structure,consequently resulting in a further red-shift towards 675 nm and enhanced photoluminescence intensity in(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+).What’s more,w-LEDs were fabricated by using blue LED chip,blue,green,red and deep red((Sr,Gd)Li(Al,Mg)_(3)N_(4):Eu^(2+))phosphors whose color rendering index were Ra 96.0 and R997.7.All above results demonstrate that the partial replacements of Sr^(2+)by Gd^(3+)and Al^(3+)by Mg^(2+)are effective methods for spectral modulation and(Sr,Gd)Li(AI,Mg)_(3)N_(4):Eu^(2+)phosphors are suitable for highquality full-spectrum WLEDs.
基金Project supported by the National Key Research and Development Program of China(2017YFB0404301)the Team of Excellent Talent Development Project of Xicheng District,Beijing.
文摘A series of non-rare earth Mn^(4+)-activated strontium aluminate phosphors Sr_(4)Al_(14)O_(25):Mn^(4+)co-doped with Sc^(3+)ions were successfully synthesized by a high-temperature solid-state reaction method.XRD result reveals that there is no introduction of additional phase but expansion of lattice with incorporation of Sc34 ions.Excitation and emission spectrum measurement shows that the synthesized phosphors can be efficiently excited by near-ultraviolet and blue light,and a deep red emission centered at 652 nm with a narrow full width at half maximum(FWHM)can be obtained,which is attributed to the transition^(2)E→^(4)A_(2)of Mn^(4+)ions.In addition,the crystal field strength parameter(Dq)and Racah parameters(B,C)and energies of states were calculated based on experimental data.Moreover,the luminous intensity of Sr_(4)Al_(14-x)SCxO_(25):Mn^(4+)is enhanced and increased by 60%compared with Mn^(4+)single incorporated sample at x=0.06.A phenomenon of redshift is observed in the excitation spectrum and discussed systematically.Finally,the mechanism of the positive effects with Sc^(3+)ions incorporated into lattice is discussed in detail.All the results suggest that the Sr_(4)Al_(13.94)Sc_(0.06)O_(25):Mn^(4+)phosphor will become one of the great candidates for backlight of LCD.
基金supported by the Program for New Material Development & Application innovative Research Team of Higher Education in Chong Qing of China (Grant No. 201042)
文摘A series of(Y_(1-y), Gdy)_(0.95-x)(P_y, V_(1-y))O_4 :0.05Eu^(3+), xBi^(3+)+phosphors have been successfully prepared by a subsection method. The crystal structure, surface morphology and luminescence properties were investigated. It was found that the sintered samples crystallized in a tetragonal crystal system with space group I_(41)/amd(a = b = 0.7119 nm, c = 0.6290 nm). The products presented rod-like morphology with length of 100-150 nm and width of 50-100 nm. A maximum peak at 619 nm(~5D_0 →~7F_2) was observed in emission spectrum of the phosphors. It was also found that co-doping of Bi^(3+)+, P5+and Gd^(3+)ions into YVO_4:Eu^(3+)can not only made the right edge of the excitation band shift to the long-wavelength region, but also increased the emission intensity at 619 nm sharply and decreased the lifetime of fluorescence decay. These results may expand the application scope of the phosphors.
基金the National Basic Research Program of China(Grant No.2014CB643801)the National Natural Science Foundation of China(Grant Nos.51572302 and 21271191)+4 种基金the Joint Funds of the National Natural Science Foundation of China and Guangdong Province(Grant No.U1301242)Teamwork Projects of Guangdong Natural Science Foundation(Grant No.S2013030012842)Guangdong Science&Technology Project(Grant No.2015B090926011)the Natural Science Foundation of Guangdong Province(Grant No.2014A030313114)China Postdoctoral Science Foundation(Grant No.2014M562237)
文摘Red phosphor K_2LiAlF_6:Mn^(4+) has been synthesized by a cation-exchange method in HF solution. To optimize their optical properties, phosphors were synthesized using different reaction conditions. The K_2LiAlF_6:0.5%Mn^(4+) synthesized at 20℃ for4 h shows the highest luminescence intensity. The temperature-dependent emission intensity of the phosphor was investigated,and it was found to exhibit good thermal stability, making it a promising red phosphor candidate for warm WLEDs.
基金Project supported by the National Natural Science Foundation of China(51972213,61605116,51972208,51802196).
文摘A series of new oxyapatite red phosphors Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O doped with different concentrations of Eu^(3+)were successfully synthesized by high temperature solid state method.The X-ray diffraction(XRD)Rietveld refinement results show that the structure of the phosphor belongs to space group P6_(3)/m and Eu^(3+)ion replaces Y^(3+)ion.The emission spectrum consists of the characteristic emission peaks corresponding to Eu^(3+)under the excitation of 274 nm and the dominant emission peak is at 614 nm(^(5)D_(0)→^(7)F_(2) of Eu^(3+)).The concentration quenching effect occurs and the optimized Eu^(3+)concentration is 4.0 mol%.The energy level diagram for luminous mechanism is also given and the non-radiative energy transfer mechanism between Eu^(3+)is mainly exchange interaction.The CIE coordinate is close to the ideal red light and the color purity is higher than 99.79%.Moreover,the phosphor exhibits moderate thermal stability because the photoluminescence intensity at 423 K is still maintained at higher than 78.97%of that at room temperature.The internal quantum efficiency of Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O:4.0 mol%Eu^(3+)phosphor is 58.2%.A red light emitting diode(LED)device based on it can emit bright red light.The CCT values of the device are basically unchanged when driven by various bias current.The results show that Ca_(3) Y_(7)(BO_(4)) (SiO_(4))_(5) O:Eu^(3+)is a new type of oxyapatite red fluorescent material with good comprehensive performances.
基金Project supported by the National Natural Science Foundation of China(51102021)the Ministry of Science and Technology of China(2014CB643801,2011AA03A101)the Beijing Nova Program(2012099)
文摘The novel nitride-based luminescent materials have received much attention since the end of the last century. In this paper, the commercial Eu2+-activated nitride red phosphors, Sr1.95 Si5 N8 :Eu0.05, Sr1.85 Si5 N8 :Eu0.15 and Ca0.99 AlSiN3 :Eu0.01 phosphors were annealed at different temperatures(beyond 300 oC) to investigate the dependence of their luminescence performance and structure variability on the temperature. By photoluminescence spectra, X-ray diffraction(XRD) and thermogravimetry-differential scanning calorimetry(TG-DSC) analysis, the high temperature stability of the hosts and activator of the three samples were disclosed. With the annealing temperature increasing, the activator Eu2+ions were firstly oxidized and then host in Sr1.95 Si5 N8 :Eu0.05 and Sr1.85 Si5 N8 :Eu0.15, but for Ca0.99 AlSiN3 :Eu0.01, only the oxidation of the host could be observed, which would lead to the luminescence degradation and even failure of these phosphors. The activator Eu2+ions were much more stable in CaAlSiN3 :Eu than Sr2 Si5 N8 :Eu due to their crystal surroundings, and its concentration also influenced the temperature stability of Sr2 Si5 N8 :Eu.
基金Project supported by Natural Science Foundation of Fujian Province (2011J033)
文摘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%.
基金Project supported by 2009 National Technical Innovation Fund for Mid and Small Size Enterprise of China (09C26214405227)2009 Huizhou Science and Technology Project of China (2009B010004008)
文摘A series of red phosphors Ca10Li (PO4)7:Eu3+ were synthesized by high temperature solid-state reaction method. Their luminescence properties were characterized by means of photoluminescence excitation and emission spectra,CIE chromaticity and quantum efficiency. Results indicated that the phosphors could be effectively excited by the near ultraviolet (NUV) light (393 nm). The main emission peaks of the phosphor were ascribed to the transition 5D0-7F2 (613 and 617 nm) of Eu3+ ion when samples were excited by 393 nm. The CIE chromaticity (x,y) of Ca9.9Li (PO4)7:0.10Eu3+ was x=0.638,y=0.361 and the quantum efficiency of this phosphor was 75% excited by 393 nm. Therefore,this phosphor could be a promising red component for the applications in white LEDs.
基金Project supported by National Natural Science Foundation of China (NSFC20803097, NSFC20603049)Natural Science Foundation of Chongqing (CSTC2011AB4056, CSTC2009BA4023)the Fundamental Research Funds for the Central Universities (CDJZR10220005 and CDJRC10220002)
文摘The Bi3+ doped molybdate-based red-emitting phosphors, LiEu1-xBix(MoO4)2, were successfully synthesized with a sol-gel method. The prepared LiEu1-xBix(MoO4)2 phosphors exhibited pure and intense red emission at 613 nm under the excitation of near-UV 394 nm. It was discussed in detail that the influence of the synthesis conditions such as the doping concentration of Bi3+, the dose of citric acid, pH of the precursor solution and the sintering temperature on the emission intensity of the phosphors. According to the results, the optimal condition was obtained: the doping concentration of Bi3+ was 15 mol.%, molar ratio of citric acid to metal ions was 1.5:1, pH of the precursor solution was 1.0 and the sintering temperature was 800 ?C. The X-ray diffraction (XRD) patterns of the LiEu0.85Bi0.15(MoO4)2 phosphor prepared under the optimal condition indicated that the phosphor was single phase with tetragonal scheelite structure. The Commission Internationale de l'E-clairage (CIE) chromaticity coordinates of LiEu0.85Bi0.15(MoO4)2 were (x=0.655, y=0.345), which were closer to the national television stan-dard committee (NTSC) standard values (x=0.670, y=0.330) than that of a commercial red phosphor of Y2O2S:Eu3+(x=0.630, y=0.350). This LiEu0.85Bi0.15(MoO4)2 red phosphor is a promising candidate for the fabrication of white light-emitting diode (W-LED) with near-UV chips.
基金Project supported by the National Natural Science Foundation of China (50372086) and the Minstry of Science and Technology of China (2006AA03A133)
文摘Eu-activated CaMoO4 phosphors were co-precipitated in an aqueous solution, and NH3·H2O, NH4HCO3 and (NH2)2CO as pre-cipitating aid agents were compared based on the morphology and particle size distribution of the phosphor samples. Sm3+ as sensitizer ion was investigated on the luminescence of CaMoO4:Eu, and it could strengthen the 406 nm absorption of this phosphor. At last, the scheelite CaMoO4:Eu and wolframite ZnMoO4:Eu were selected to compare their host absorption. The result showed that the scheelite molybdate host exhibited stronger UV absorption than wolframite one.
基金Project supported by National Natural Science Foundation of China(51202053)Natural Science Foundation of Hebei Province(Q2012061)China Postdoctoral Science Foundation(2013M530884)
文摘A series of novel Sm3+-doped LiY(MoO4)2 red phosphors under the UV excitation were synthesized by solid state reaction at 800 oC for 7 h. The data measured by X-ray diffraction(XRD) indicated that the samples were all pure phases of LiY(MoO4)2. Their excitation spectra had a broad band ranging from 250 to 350 nm and several sharp peaks. The centers of the peaks were located at about 365 nm(6H5/2→4D3/2), 378 nm(6H5/2→6P7/2), 406 nm(6H5/2→4F7/2), 420 nm(6H5/2→6P5/2), 442 nm(6H5/2→4G9/2), 471 nm(6H5/2→4I13/2) and 482 nm(6H5/2→4I9/2), respectively. The strongest emission was excited by 406 nm, and the main emissions were located at 568 nm(4G5/2→6H5/2), 610 nm(4G5/2→6H7/2), 649 nm(4G5/2→6H9/2) and 710 nm(4G5/2→6H11/2). Photoluminescence properties were determined for various concentrations of Sm3+-doped LiY(MoO4)2 host, and the luminescence intensity had the best value when x=0.02 in LiY1–x(MoO4)2:xSm3+.
基金supported by National Natural Science Foundation of China(21271139)
文摘CaTiO3:Eu3+ red phosphors were prepared using H3BO3 assisted solid state synthesis.The structure and morphology of the obtained sample were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).And the luminescence property was measured using photoluminescence excitation (PLE) and photoluminescence (PL) spectra,respectively.In the excitation spectra,main excitation peaks of the prepared samples were centered at 397 and 465 nm,revealing that these phosphors could be excited by commercial GaNand InGaN-typed light emitting diodes (LEDs).Dominant emission peaks of the phosphors were located at 616 nm,owing to the transition of 5D0→7F2 of Eu3+.In the optimum condition,CaTiO3:3%Eu3+ phosphor was obtained at a sintering temperature of 1200 ℃ in air with a content of 20 mol.% H3BO3 addition.When excited by 397 nm irradiation,the PL intensity of as-prepared red phosphor was 2.2 times higher than that of samples obtained by traditional solid state synthesis,while the PL intensity was 3 times higher than that excited by 465 nm irradiation.The added H3BO3 improved the crystallinity,and increased the color purity,implying the potential to be a promising red phosphor in white light emitting diodes (WLEDs).
基金Supported by the Key Programs for Science and Technology Development of Hubei Province(Grant No.2005AA105A05)
文摘A series of novel red phosphors LiEu1-xYx(WO4)0.5(MoO4)1.5 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8) were synthesized by conventional solid state reaction method with the starting materials: WO3, MoO3, Eu2O3, Li2CO3 and Y2O3. The spectrum and the crystal structure of the phosphors were characterized by F-4500 and XRD respectively. Meanwhile the effects of flux and Y3+ concentration on the crystal structure and luminescent properties of the phosphors were investigated. The results showed that the optimal content of flux (WAlF3/WH3BO3=1/1) was 1 wt% and the optimal doping concentration of Y3+ was 0.5 mol. The emission spectrum showed the most intense peak was located at 615 nm, which corresponds to the 5D0→7F2 transition of Eu3+ and that Eu3+ occupied the lattice site of noncentrosymmetric environment in the scheelite phases. The excitation spectrum displayed that these phosphors could be effectively excited by ultraviolet (UV) (396 nm) and blue (466 nm) light, nicely in correspondence with the widely ap- plied output wavelengths of ultraviolet or blue LED chips. The influence of flux on the luminescent properties of LiEu0.5Y0.5(WO4)0.5(MoO4)1.5 phosphor was analyzed. The XRD spectra indicated that the flux could help to crystallize the phosphor, and no other phases were formed except the tetragonal. When adding flux, the relative intensity of LiEu0.5Y0.5(WO4)0.5(MoO4)1.5 became much stronger and the average particle size of the phosphor decreased.
基金Project supported by MOST of China (2006CB601104)Synchrotron Radiation Fund of Innovation Project of Ministry of Education (20041213S)
文摘Red phosphor (Y, Gd)BO3:Eu3+ with grain shape, small size, non-agglomerate, high crystallinity and good photoluminescence (PL) intensity was prepared by a complex method that the precursor of the phosphor was prepared by co-precipitation method and the phosphor was prepared by combustion method. The SEM photos and the photoluminescence spectrum excited under VUV show that the morphology and luminescent properties of this phosphor are satisfied when an appropriate amount of urea was adopted as the combustion agent in the preparation procedure.
