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1.
This work presents the synthesis of Y 2O 3:Eu 3+, xCa 2+ ( x = 0 mol%, 1 mol%, 3 mol%, 5 mol%, 7 mol%, 9 mol%, 11 mol%) nanophosphors with enhanced photoluminescence properties through a facile solution combustion method for optoelectronic, display, and lighting applications. The X-ray diffraction (XRD) patterns of the proposed nanophosphor reveal its structural properties and crystalline nature. The transmission electron microscope (TEM) results confirm the change in the shape of the particle and aggregation of particles after co-doping with Ca 2+. Fourier transform infrared spectroscopy (FTIR) and Raman vibrations also confirm the presence of Y–O vibration and subsequently explain the crystalline nature, structural properties, and purity of the samples. All the synthesized nanophosphors samples emit intense red emission at 613 nm ( 5D 0→ 7F 2) under excitation with 235, 394 and 466 nm wavelengths of Eu 3+ ions. The photoluminescence (PL) emission spectra excited with 235 nm illustrate the highest emission peak with two other emission peaks excited with 466 and 394 nm that is 1.4 times higher than 466 nm and 1.9 times enhanced by 394 nm wavelength, respectively. The emission intensity of Y 2O 3:Eu 3+, xCa 2+ (5 mol%) is increased 8-fold as compared to Eu:Y 2O 3. Doping with Ca 2+ ions enhances the emission intensity of Eu:Y 2O 3 nanophosphors due to an increase in energy transfer in Ca 2+→Eu 3+ through asymmetry in the crystal field and by introduction of radiative defect centers through oxygen vacancies in the yttria matrix. It is also observed that the optical band gap and the lifetime of the 5D 0 level of Eu 3+ ions in Y 2O 3:Eu 3+, xCa 2+ nanophosphor sample gets changed with a doping concentration of Ca 2+ ions. Nanophosphor also reveals high thermal stability and quantum yield as estimating activation energy of 0.25 eV and 81%, respectively. CIE, CCT, and color purity values (>98%) show an improved red-emitting nanophosphor in the warm region of light, which makes this material superior with a specific potential application for UV-based white LEDs with security ink, display devices, and various other optoelectronics devices. 相似文献
2.
Eu 2+ activated phosphors with the composition of Ca 013Sr 0.87Al 2Si 2O 8 were synthesized by combustion technique. The luminescent properties of these phosphors have been explored by analyzing their excitation and emission spectra with the help of photoluminescence (PL) spectroscopy. The phase-forming processes and presence of associated mode of vibrations of the phosphors were studied by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) respectively. Under ultra-violet (UV) excitation, Ca 013Sr 0.87Al 2Si 2O 8 phosphors had broad emission spectrum between 418 and 550 nm in the blue-green region of spectra corresponding to 4f 65d→4f 7 transition of Eu 2+ ion. The results show Ca 013Sr 0.87Al 2Si 2O 8: Eu 2+ is a promising host candidate for the phosphors and can be used for improving the efficiency and quality of phosphor-converted white light-emitting diodes. 相似文献
3.
N-containing Ce 2Si 2.5Al 0.5O 3.5N 3.5 (CeSiAlON) melilite was synthesized at 1550 and 1600 °C for 5 h from CeO 2, Si, Al, and Al 2O 3 in nitrogen by using Y 2O 3 and transition-metal nitrates (Co(NO 3) 2∙6H 2O and Ni(NO 3) 2∙6H 2O) as additives. The effects of Y 2O 3 and transition-metal nitrates on the phase, microstructures and photoluminescence properties of CeSiAlON melilite were studied. The incorporation of Y 2O 3 can promote the reaction of raw materials to a low degree, and results in a unit cell shrinkage of CeSiAlON due to the smaller radius of Y atom than that of Ce atom. The transition-metal nitrates can accelerate the reaction clearly and facilitate the formation of CeSiAlON fibers. The photoluminescence (PL) properties of CeSiAlON melilite presents a board violet emission band because of the 5d-4f transitions of Ce 3+, and the additives can enhance the PL emission intensities of specimen significantly. 相似文献
4.
The dense monoclinic-SrAl 2Si 2O 8 ceramics have been prepared by a two-step sintering process at a sintering temperature of 1173 K (900 °C). Firstly, the pre-sintered monoclinic-SrAl 2Si 2O 8 powders containing small SiO 2·Al 2O 3 crystal phases were obtained by continuously sintering a powder mixture of SrCO 3 and kaolin at 1223 K (950 °C) for 6 hours and 1673 K (1400 °C) for 4 hours, respectively. Subsequently, by the combination of the pre-sintered ceramic powders with the composite flux agents, which are composed of a SrO·3B 2O 3 flux agent and α-Al 2O 3, the low-temperature densification sintering of the monoclinic-SrAl 2Si 2O 8 ceramics was accomplished at 1173 K (900 °C). The low-temperature sintering behavior and microstructure evolvement of the monoclinic-SrAl 2Si 2O 8 ceramics have been investigated in terms of Al 2O 3 in addition to the composite flux agents. It shows that due to the low-meting characteristics, the SrO·3B 2O 3 flux agent can urge the dense microstructure formation of the monoclinic-SrAl 2Si 2O 8 ceramics and the re-crystallization of the grains via a liquid-phase sintering. The introduction of α-Al 2O 3 to the SrO·3B 2O 3 flux agent can apparently lead to more dense microstructures for the monoclinic-SrAl 2Si 2O 8 ceramics but also cause the re-precipitation of SiO 2·Al 2O 3 compounds because of an excessive Al 2O 3 content in the SrO·3B 2O 3 flux agent. 相似文献
5.
A novel orange-red emitting Ba 3Y 4O 9:Sm 3+ phosphors were prepared by a high temperature solid-state reaction in air. X-ray diffraction (XRD), photoluminescence spectra, fluorescence decay and temperature-dependent emission spectra were utilized to characterize the structure and luminescence properties. The results show that the excitation spectrum includes a series of linear peaks at 350, 367, 382, 410, 424, 445, 470 and 495 nm, respectively. Under 410 nm excitation, the emission peaks were located at 574 nm ( 4G 5/2— 6H 5/2), 608 nm ( 4G 5/2— 6H 7/2), 659 nm ( 4G 5/2— 6H 9/2) and 722 nm ( 4G 5/2— 6H 11/2), respectively. The concentration quenching occurs when x equals 0.08 for Ba 3Y 4–xO 9: xSm 3+ phosphor and its mechanism is ascribed to the dipole–dipole interaction. The chromaticity coordinates of Ba 3Y 3.92O 9:0.08Sm 3+ phosphor are in the orange-red region. The temperature-dependent study shows that this phosphor has excellent luminescence thermal-stability. And the luminescence intensity of Ba 3Y 3.92O 9:0.08Sm 3+ phosphor at 473 K only declines by about 25.75% of its initial intensity. The experimental data indicate that Ba 3Y 4O 9:Sm 3+ phosphor may be promising as an orange-red emitting phosphor for white light emitting diodes. 相似文献
6.
A series of red-emitting phosphors of CaBi 2Ta 2O 9:Pr 3+ and CaBi 2Ta 2O 9:Eu 3+ were synthesized by the solid-state reaction method. The crystal structure and photoluminescence properties were investigated by X-ray diffraction (XRD) and photoluminescence spectra. The emission spectra showed that the red emission peaks were located at 622 nm for Pr 3+ and 615 nm for Eu 3+, respectively. The optimal doping concentrations for Ca 1?xBi 2Ta 2O 9: xPr 3+ and Ca 1?yBi 2Ta 2O 9: yEu 3+ were x=0.02 and y=0.15, respectively. The effect of fluxes (H 3BO 3, NH 4F, CaCl 2 and CaF 2) and charge compensations (Li 2CO 3, Na 2CO 3 and K 2CO 3) on luminescent properties were investigated in detail. It was found that the relative emission intensity of Ca 0.98Bi 2Ta 2O 9:0.02Pr 3+ with 10 mol.% H 3BO 3 flux was about 2.9 times higher than that of the sample without flux. The relative emission intensity of Ca 0.7Bi 2Ta 2O 9:0.15Eu 3+, 0.15K + was about the 2.1 times higher than that of Ca 0.85Bi 2Ta 2O 9:0.15Eu 3+. 相似文献
7.
In this work, the Gd 3+/Eu 3+ activated Ba 3Y 4O 9 (BYO) phosphors were successfully synthesized via coprecipitation method at 1400 °C. The precursor composition, crystal structure stability, microscopic morphology, photoluminescence (PL)/photoluminescence excitation (PLE) spectra and fluorescence attenuation analysis of the phosphors are discussed in detail. The chemical composition of the precursor was determined by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetry (TG) analysis; According to field emission-scanning electron microscopy (FE-SEM) analysis, it is found that the particle size of phosphor is uniform and the agglomeration is few. According to PL/PLE spectra analysis, Ba 3Y 3.28Eu 0.6Gd 0.12O 9 phosphors has the strongest excitation band at 260 nm and the strongest emission band at 614 nm, and the fluorescence intensity of Ba 3Y 3.28Eu 0.6Gd 0.12O 9 is higher than that of Ba 3Y 3.4Eu 0.6O 9. The quenching concentration of Eu 3+ in Ba 3Y 3.88–4xEu 4xGd 0.12O 9 phosphors is x = 0.15 and the mechanism of quenching concentration of Eu 3+ is electric dipole-quadrupole type interactions. The lifetime value of Ba 3Y 3.88–4xEu 4xGd 0.12O 9 ( x = 0.15) phosphors is 0.686 ms and decreases with the increase of Eu 3+ content. In addition, the CIE chromaticity diagram of Ba 3Y 3.28Eu 0.6Gd 0.12O 9 phosphors is (0.66, 0.34). Finally, the lamp beads assembled with Ba 3Y 3.28Eu 0.6Gd 0.12O 9 phosphors have an ideal luminous effect. Therefore, the Ba 3Y 3.88–4xEu 4xGd 0.12O 9 phosphors designed in this work may hopefully meet the requirements of various lighting and optical display applications. 相似文献
8.
The Ba_(0.96)Ca_(0.04)Ti_(0.90)Sn_(0.10)O_3-xNd_2 O_3(x = 0-0.08%) ceramics were prepared via traditional solid-state sintering method. The influences of Nd3+ substitution on the phase structure, dielectric properties,piezoelectric and ferroelectric properties of the ceramics were investigated. All the samples possess pure BaTiO_3-type perovskite structure. MPB with orthorhombic and tetragonal phase coexist at around x = 0.03-0.04. Nd~(3+) doping decreases both Tc and T_(O-T) to lower temperature. All the samples exhibit an intermediate state with the coexistence of ferroelectric and diffuse relaxor ferroelectric behavior with the addition of Nd~(3+). The electric properties of the ceramics were optimized at x = 0.03 with d33, K_p, ε_r and P_r values of 545 pC/N, 51.9%, 24,412 and 10.74 μC/cm~2. 相似文献
9.
Novel nanosized Y2WO6:Eu3+ phosphors were synthesized via a co-precipitation reaction. The crystal structure of Y2WO6:Eu3+sample was monoclinic phase characterized by using X-ray diffraction (XRD). The... 相似文献
10.
Two-step synthesis of Y2〇3:Eu nanostructures was performed. It includes microwave driven hydrothermal and calcination stages. Performed route results in crystallization of Y4〇(OH)g(N〇3):Eu crystals initially, then Y2〇3:Eu crystals after calcination. Arranged Eu contents in relation to overall cation quantity were set to 2 mol%, 10 mol% and 20 mol%. Varying europium concentrations influence habit of obtained Y4〇(OH)g(N〇3):Eu crystals from needle-like to plate-like and as a result, also shapes of final Y2〇3:Eu nanostructures. Additionally, certain amount of Eu2+ ions was detected in as-grown material using laser spectroscopy and decay kinetics measurements. Obtained material was calcined at 1200 °C in the air, which results in oxidation of Eu2+ ions and crystallization of small number of cubic EU2 O3 nanocrystals. Characterization of obtained materials was performed using XRD, SEM, TEM, EDX, CL,Raman and photoluminescence spectroscopy. 相似文献
11.
In this investigation, Ba2CaZn2Si6O17:Eu2+ phosphor (BCZSOE) was successfully synthesized through the facile solid-state approach. Accordingly, spherical/commercial SiO2 particles were used through synthesizing BCZSOE phosphors. The crystal structure and microstructure of the produced phosphors were characterized using powder X-ray diffraction, field emission scanning electron microscope and high-resolution transmission electron microscope (HRTEM) instruments, while the luminescence properties of BCZSOE materials were analyzed by a photoluminescence (PL) analyzer. It was interestingly found that the use of spherical silica resulted in an uniform grain size distribution of BCZSOE phosphor in the range of 120–180 nm. In addition, the HRTEM images showed that the soaking time within the solid-state procedure was one of the most important parameters for the successful synthesis of BCZSOE compound. The luminescence emission spectra revealed that the use of silica spheres gave rise to the enhanced emission intensity than that of commercial silica particles. In addition, it was concluded that the emission bands at the wavelengths of 447 and 505 nm were due to the substitution of Ca2+ and Ba2+ by Eu2+ ions, respectively. 相似文献
12.
To upgrade the electric properties of lead-free piezoceramics, (1– x)(Ba 0.98Ca 0.02Ti 0.94Sn 0.04Zr 0.02)O 3- xY 2O 3 (abbreviated as (1– x)BCTSZ- xY, x = 0 mol%, 0.02 mol%, 0.04 mol%, 0.06 mol%, 0.08 mol% and 0.1 mol%) ceramics were successfully synthesized by traditional solid-state sintering method. The phase structure and microstructure of ceramics were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and piezoresponse force microscopyeramics (PFM). The electric properties of ceramics were researched through piezoelectric, dielectric and ferroelectric test instruments. The results show that all samples have pure perovskite structure and favorable electric properties. The optimal electric properties which especially include superior ferroelectric properties are gained when Y 2O 3 content is 0.06 mol% ( d33 = 419 pC/N, kp = 52%, Tc = 89.5 °C, εr = 26900, tan δ = 2.86%, Pr = 14.41 μC/cm 2, Ec = 1.8 kV/cm). Moreover, the temperature-dependent dielectricity of samples shows apparent relaxor behavior under different frequencies. The Curie–Weiss law further proves that all samples are typical relaxor ferroelectrics, and the relaxor degree of samples decreases with increase of Y 2O 3 content. In conclusion, Y 2O 3 plays a significant role in enhancing electric properties of BCTSZ ceramics. 相似文献
13.
A novel green-emitting phosphor,Eu2+-doped Ca2-x/2 Si1-x Px O4(0.25≤x≤0.30),was prepared through a conventional solidstate reaction.X-ray diffraction(XRD),photoluminescence(PL) and decay studies were employed to characterize the sample,which was assigned to P63mc space group in the hexagonal system.The effect of P-doping on the α-Ca2 SiO4 was studied and P2 O5 broken down by the raw material of(NH4)2 HPO4 played an important role in stabilizing α-Ca2 SiO4 which can only be stable at high temperature.The XRD patterns of the Ca2-x/2 Si1-x Px O4 host were found pure and optimized when the mole fraction of P2 O5 was 14.5%.The diffuse reflectance spectra of the Ca1.855 Si0.71 P0.29 O4 and Ca1.845 Si0.71 P0.29 O4 :0.01Eu2+covered the spectral region of 230-400 nm,implying that the phosphor was suitable for UV or near-UV LED excitation.The phosphor could be effectively excited in the near UV region with the maximum at 372 nm.The emission spectrum of the Ca1.845 Si0.71 P0.29 O4 :0.01Eu2+phosphor showed an asymmetrical single intensive band centered at 513 nm,which corresponded to the 4f65d1→4f7transition of Eu2+.Eu2+ions might occupy two types of Ca2+sites in the Ca1.855 Si0.71 P0.29 O4 lattice and form two corresponding emission centers,which led to the asymmetrical emission of Eu2+in Ca1.855 Si0.71 P0.29 O4.The effects of Eu2+-doped concentration in Ca1.855-x Si0.71 P0.29 O4 :xEu2+on the PL were also discussed,the optimum doping concentration of Eu2+was 1 mol.% and the critical distance of the energy transfer was also calculated by the concentration-quenching method.The non-radiative energy transfer between Eu2+seemed to be caused by the multipole-multipole interaction.The fluorescence lifetime of Eu2+was found to be 0.55711 μs.The results suggested that these phosphors might be promising candidates used for near UV light excited white LEDs. 相似文献
14.
By employing an electrochemical technique involving stabilized zirconia as solid electrolyte and Mo + MoO 2 mixture as reference electrode, the equilibrium oxygen partial pressures for three-phase assemblages of CaSiO 3(s) + Ca 3Si 2O 7(s) + {CaO + SiO 2 + Fe xO} melt and Ca 3Si 2O 7(s) + Ca 2SiO 4(s) + {CaO + SiO 2 + Fe xO} melt were determined as: - log { PO2 (CS + C 3S 2 + L)/bar} = - 3.22 13000/( T/K) ± 0.05 - log { PO2 (C 3S 2 + C 2S + L)/bar} = - 0.92 16400/ ( T/K) ± 0.04. respectively, where CS, C 3S 2 and C 2S indicate CaSiO 3(s), Ca 3Si 2O 7(s). and Ca 2SiO 4(s), respectively. 相似文献
15.
The red long-time luminescent material Y 2O 2S:Eu 3+, 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 Y 2O 2S, 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. 相似文献
16.
A series of new oxyapatite red phosphors Ca 3Y 7(BO 4)(SiO 4) 5O 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 ( 5D 0→ 7F 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 3Y 7(BO 4)(SiO 4) 5O: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 3Y 7(BO 4)(SiO 4) 5O:Eu 3+ is a new type of oxyapatite red fluorescent material with good comprehensive performances. 相似文献
17.
The orange-red long afterglow phosphors Y 2O 2S:Sm 3+, Mg 2+, Ti 4+ was prepared by high temperature solid-state method. By XRD analysis, the crystal phase of the sample was Y 2O 2S, belonging to hexagonal system, and no new crystal phase arose when doping Sm 3+, Mg 2+, Ti 4+. The characteristic peaks of excitation spectrum were located at 373, 388, 417, 430, 475 and 491 nm, and the characteristic peaks of emission spectrum were located at 571, 609 and 657 nm. The content of Sm 3+ and doped ions Mg 2+, Ti 4+ affected the luminescent properties obviously, and Sm 3+ affected the luminescent brightness mainly. Mg 2+ and Ti 4+ could deepen properly trap energy of Y 2O 2S crystal and strengthen its afterglow properties, the brightness and afterglow properties of sample were better when the mole ratio of Sm/Y, Mg/Y and Ti/Y is 1.4%, 1.25% and 0.9%, respectively. 相似文献
18.
Compared with Y 3Al 5O 12:Ce 3+,Y 3MgAl 3SiO 12:Ce 3+(YMASG:Ce 3+) reveals great potential for highpower white lighting with red-shift spectrum.Herein,YMASG:Ce 3+ transparent ceramics were explored to be synthesized in the air following hot isostatic pressure(HIP) treatment to obtain tunable and optimized optical properties.Then phase purity,microstructure,transmittance,and photoluminescence of YM... 相似文献
19.
BaO-Y 2O 3-TiO 2 microwave dielectric ceramics with the rich area of TiO 2 were fabricated by a solid-state reaction method using BaCO 3, Y 2O 3, TiO 2 powders as starting materials. The sintering characteristics, phase composition, micro-structures and microwave dielectric properties of BaO-Y 2O 3-TiO 2 microwave dielectric ceramics with different k values sintered at different temperatures were investigated. The results showed that the sintering temperature of BaO-Y 2O 3-TiO 2 microwave dielectric ceramics was lower (about 1240 °C), and the sintered ceramics with the major phase of Y 2Ti 2O 7 had excellent dielectric properties. When k = 4, ɛ r and tanδ were about 78.3 and 3 × 10 −3 respectively. When k=5, ɛ r and tanδ were about 53 and 9 × 10 −4 respectively. 相似文献
20.
As a cyan-emitting oxonitridosilicate phosphor,BaSi 2O 2N 2:Eu 2+can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting.The replacements of Ba 2+by Lu 3+and Ba 2+-Si 4+by Lu 3+-Al 3+can greatly increase the luminescence intensity and improve the thermal stability at the same time.With Lu 3+doping,the internal quantum efficiencyηIQE Ba 0.925Si 2O 2N 2:0.03 Eu 2+,0.045 Lu 3+is 24.08%higher than that of Ba 0.97Si 2O 2N 2:0.03 Eu 2+.After Al 3+co-doping,theηIQE is further increased by 10.31%compared to Ba 0.925Si 2O 2N 2:0.03 Eu 2+,0.045 Lu 3+.When the temperature rises to 473 K,the luminescence intensity of Ba 0.925Si 2O 2N 2:0.03 Eu 2+,0.045 Lu 3+maintains 62.32%of that at room temperature,which increases by 17.35%in relative to the Ba 0.97Si 2O 2N 2:0.03 Eu 2+,while the luminescence intensity of Ba 0.925Si 1.97O 2N 2:0.03 Eu 2+,0.045 Lu 3+,0.03 Al 3+keeps 73.87%of the initial value,which increases by18.52%compared to Ba 0.925Si 2O 2N 2:0.03 Eu 2+,0.045 Lu 3+.The mechanisms for luminescence and thermal stability improvement are proposed.The Ba 0.925Si 1.97O 2N 2:0.03 Eu 2+,0.045 Lu 3+,0.03 Al 3+cyan phosphor,Y3 Al5 O12:Ce3+yellow phosphor and CaAlSiN3:Eu 2+red phosphor are mixed thoroughly and coated on a blue LED(450 nm)to assemble a WLED.The WLED demonstrates a color rendering index(Ra)of 97.1 at150 mA,and the R1-R15 values are all above 90.The results indicate that as an effective cyan compensator in WLED,the BaSi 2O 2N 2:Eu 2+,Lu 3+,Al 3+phosphor has great application prospect in the field of full-spectrum lighting. 相似文献
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