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1.
Using the solid‐state reaction method, Ce3+,Tb3+‐coactivated Si5AlON7 (Si6?zAlzOzN8?z, = 1) phosphors were successfully synthesized. The obtained phosphors exhibit high absorption and strong excitation bands in the wavelength range of 240–440 nm, matching well with the light emitting‐diode (LED) chip. The ET from Ce3+ to Tb3+ ions in Si5AlON7:Ce3+,Tb3+ has been studied and demonstrated by the luminescence spectra and decay curves. Moreover, the phosphors show tunable emissions from blue to green by tuning the relative ratio of the Ce3+ to Tb3+ ions. Thermal quenching properties of Si5AlON7:Ce3+,Tb3+ had also been investigated and the quenching temperature is ~190°C. These results show that Si5AlON7:Ce3+,Tb3+ could be a promising candidate for a single‐phased color‐tunable phosphor applied in UV‐chip pumped LEDs.  相似文献   

2.
A new borate phosphor NaBaY(BO3)2: Ce3+, Tb3+ (NBY:Ce3+, Tb3+) was successfully synthesized under low temperature designed to put into application in the fields of ultraviolet (UV)‐excited light emitting diodes (LEDs) and field emission displays (FEDs). The structure distortion between Ce3+, Tb3+ single‐ and co‐doping NBY was discussed by X‐ray powder diffraction Rietveld refinement, high‐resolution transmission electron microscopy (HRTEM) and spectra. NBY: Ce3+, Tb3+ presents a wide absorption band ranging from 310 to 400 nm and efficient green emission (λmax = 542 nm) with a full‐width at half‐maximum of 3.3 nm. The remarkable thermal stability has also been tested, indicating that the intensity at 200°C is still beyond 70% of the original intensity. In addition, a white LED device was manufactured by connecting a 370 nm UV chip with a blend of BaMaAl10O17: Eu2+ (BAM: Eu2+), NBY: Ce3+, Tb3+ and CaAlSiN3: Eu2+. The color coordinate, correlated color temperature and color rendering index of the manufactured LED device were (0.335, 0.347), 5511 K and 80.16, respectively. Meanwhile, the cathodoluminescence (CL) spectra under the various conditions of probe currents and accelerating voltages were also analyzed. Through successive excitation of low‐voltage electron‐beam, the wonderful performances of degradation property and color stability were obtained. These results suggest that the green‐emitting NBY: Ce3+, Tb3+ phosphor has the prospect of becoming applications in white UV LEDs and FEDs.  相似文献   

3.
A series of newly developed color‐tunable Ca3La6(SiO4)6: Ce3+, Tb3+ phosphors were successfully prepared in this study. The crystal structures of the prepared phosphors were revealed to be hexagonal with space group P63/m, and the lattice parameters were evaluated via utilizing the Rietveld refinement method. Upon excitation at 288 nm, the emission spectra of Ce3+and Tb3+ ions co‐doped Ca3La6(SiO4)6 phosphors included a blue emission band and several emission lines. The blue emission band with a peak at 420 nm originated in the fd transitions of Ce3+ ions, and the emission lines in the range of 450–650 nm were assigned to the 5D4 → 7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions. Increasing the doping content of Tb3+ ions considerably strengthened Tb3+ emission and reduced Ce3+ emission owing to the energy transfer from Ce3+ to Tb3+ ions. The mechanism of the energy transfer was confirmed to be a dipole–dipole interaction. The effective energy transfer from Ce3+ to Tb3+ ions caused a color shift from purplish‐blue to yellowish‐green. Color‐tunable Ca3La6(SiO4)6: Ce3+, Tb3+ phosphors have the potential to be utilized in light‐emitting diodes with proper modulation of the amount of Tb3+ ions.  相似文献   

4.
《Ceramics International》2016,42(15):16626-16632
A series of Ce3+ doped and Ce3+/Mn2+ co-doped calcium zirconium silicate CaZrSi2O7 (CZS) phosphors have been synthesized via conventional high temperature solid state reactions. The luminescence properties, energy transfer between Ce3+ and Mn2+ have been investigated systematically. Under 320 nm excitation, the phosphor CZS: 0.05Ce3+ exhibit strong blue emission ranging from 330 nm to 500 nm, attributed to the spin-allowed 5d-4f transitions of Ce3+ ions. There are two different emission centers of Ce3+ ions, Ce3+(I) and Ce3+(II). The emission spectra of Ce3+, Mn2+ co-doped phosphors shows a broad emission around 550 nm corresponding to the 4T1(4G)-6A1(6S) spin-forbidden transition of Mn2+. The energy transfer between Ce3+ and Mn2+ is detected and the transfer efficiency of Ce3+(II) to Mn2+ is faster than that of Ce3+(I) to Mn2+. The resonant type is identified via dipole-dipole mechanism. Additionally, a blue-shift emission of Ce3+ and a red-shift emission of Mn2+ have been observed following the increase of Mn2+ content in relation to the energy transfer. Thermal quenching has been investigated and the emission spectra show a blue-shift with the temperature increases, which have been discussed in details. CZS: 0.05Ce3+, yMn2+ phosphors can be tuned from blue to white and even to yellow by adjusting the Mn2+ content. All the results indicate that CZS: Ce3+, Mn2+ phosphor have a potential application for near-UV LEDs.  相似文献   

5.
Superior optical, thermal, and mechanical properties of transparent ceramics are very important in the applications of solid lasers, solid‐state lighting, and transparent armors. Herein, a series of (Dy0.03CexY0.97?x)3Al5O12 transparent ceramics were fabricated using vacuum reactive sintering method. Importantly, these Dy3+/Ce3+ codoped yttrium aluminum garnet (YAG) transparent ceramics served as single‐composition tunable white‐light phosphors for UV‐LEDs is developed for the first time. By combining with commercially available UV‐LEDs directly, the optimal chromaticity coordinates and correlated color temperature (CCT) are (x = 0.33, y = 0.35) and 5609 K, respectively. Notably, the codoping of Ce3+ enhances the luminescent intensity of Dy3+ ions while excited at 327 nm. The emission color of YAG transparent ceramics can be tuned from white to yellow through energy transfer between Dy3+ and Ce3+. These new phosphors, possessing of pure CIE chromaticity and environmentally friendly nature, are promising for applications in white UV‐LEDs.  相似文献   

6.
A series of phosphors Ca12(0.97?x)Al14O32F2: 0.03Ce3+, xTb3+ have been prepared by a hightemperature solid‐state reaction using boric acid as flux. These oxyfluorides crystallize in cubic structure, space group. Under the near ultraviolet excitation within wavelength range 310–390 nm, Ca12(0.97?x)Al14O32F2: 0.03Ce3+, xTb3+ phosphors exhibit an intense emission covering a broad band of 370–500 nm derived from the 5d→4f transitions of Ce3+ and a characteristic emission at 544 nm of Tb3+. The emission can be tuned from blue to green by altering the relative ratio of Ce3+ to Tb3+ in the composition. The energy‐transfer mechanism from Ce3+ to Tb3+ is investigated based on the site occupancy of the luminescence center in the crystal structure of the Ca12Al14O32F2 host. More importantly, when a certain amount of boric acid is added as flux in the synthesis, the fluorescence intensity of the phosphors increases about 65%. Because of its broad excitation and efficiently tunable blue to green luminescence, the Ca12(0.97?x)Al14O32F2: 0.03Ce3+, xTb3+ phosphors may find promising application as a near UV‐convertible phosphor for white‐light‐emitting diodes.  相似文献   

7.
Uniform orange‐to‐red spherical phosphors of Sr2P2O7:Ce3+, Mn2+ have been synthesized by the co‐precipitation method and characterized by X‐ray powder diffraction, scanning electron microscopy, and photoluminescence spectroscopy. The results indicate that the morphology, size, and photoluminescence properties of Sr2P2O7:Ce3+, Mn2+ phosphors can be effectively controlled by the reaction and the sintering temperatures. Energy transfer from Ce3+ to Mn2+ in Sr2P2O7 phosphor was observed from photoluminescence spectra of Sr2P2O7:Ce3+, Sr2P2O7:Mn2+, and Sr2P2O7:Ce3+, Mn2+. Moreover, based on a self‐assembly process, a possible formation mechanism for the spherical phosphors is proposed. The uniform phosphor spheres obtained in this work exhibit great potential for high‐resolution display devices such as light emitting diodes.  相似文献   

8.
Ce3+, Nd3+ codoped (Sr0.6Ca0.4)3(Al0.6Si0.4)O4.4F0.6 phosphors were synthesized through the high‐temperature solid‐state reaction method. Luminescence spectra, absorption spectra, and decay lifetimes of these samples have been measured to prove the energy‐transfer process from Ce3+ to Nd3+. Under UV and blue light excitation, (Sr0.6Ca0.4)3(Al0.6Si0.4)O4.4F0.6:Ce3+,Nd3+ phosphors exhibit near‐infrared (NIR) emission, mainly peaking at 1093 nm and secondarily at 916 nm. The NIR emission matches well with the band gap of c‐Si. Results of this work suggest that the (Sr0.6Ca0.4)3(Al0.6Si0.4)O4.4F0.6:Ce3+, Nd3+ phosphors have potential application as down‐shifting luminescent convertor for enhancing the photoelectric conversion efficiency of c‐Si solar cell.  相似文献   

9.
《Ceramics International》2016,42(8):9396-9401
Ce3+ and Yb3+ co-doped YBO3 phosphors were facilely fabricated by a hydrothermal method. The investigations reveal that hexagonal YBO3: Ce3+, Yb3+ nanoparticles aggregate to form cyclic structure after annealing at 900 °C. An efficient near-infrared (NIR) quantum cutting phenomenon involving the emission of two NIR photons (971 nm) for each ultraviolet (UV) photon (360 nm) absorbed is observed based on the cooperative energy transfer (CET) from Ce3+ to Yb3+ in YBO3 with a CET efficiency of 41.9%. Moreover, YBO3: Ce3+, Yb3+/SiO2 films with anti-reflection and NIR quantum cutting abilities were prepared by dip-coating method. The as prepared composite films can convert UV photons into NIR photons between 950 nm and 1050 nm, which well matched with the spectral response of the silicon-based solar cell. The experimental results indicate that the photoelectric conversion efficiency of silicon solar cell can be effectively improved by assembling the YBO3: Ce3+, Yb3+/SiO2 bi-functional film, and the corresponding conversion efficiency is about 0.521% higher than the pure glass and 0.252% higher than the pure SiO2 anti-reflection (AR) film. In a word, this work provides a simple strategy to develop optical films with AR and NIR quantum cutting abilities for solar energy conversion.  相似文献   

10.
A modified chemical vapor deposition (CVD) technique is used to synthesize the color‐tunable siliconitride Sr2‐1.5x‐yCexEuySi5N8 (x = 0.000‐0.016 and y = 0.000‐0.020) phosphors. In comparison with the conventional solid‐state method, the CVD approach successfully improved the crystallinity, particle size distribution, and photoluminescence through the enhanced gas‐solid reaction. Under blue excitation, Sr1.98Eu0.02Si5N8 exhibited a red emission band at 618 nm. The incorporation of Ce3+ ions increased the emission intensity of Eu2+ ions by approximately 10% owing to the enhanced absorption and dipole‐dipole energy transfer process from Ce3+ to Eu2+ ions. It resulted in a shift of the emission colors from yellow to red region. The external and internal quantum efficiencies of Sr1.906Ce0.06Eu0.004Si5N8 were calculated as 54% and 70%, respectively. The activation energy of thermal stability for Sr1.906Ce0.06Eu0.004Si5N8 was evaluated as 0.31 eV. A white LED with a color rendering index of 80 and a CCT of 4964 K was successfully fabricated with the present phosphors. The current research demonstrated a new series of Sr2Si5N8:Ce3+, Eu2+ phosphors with color‐tunability for fabricating white LEDs with high color‐rendering index.  相似文献   

11.
A series of novel green emission Whitlockite‐type Ca8ZnLa(PO4)7:Eu2+ and color tunable Ca8ZnLa(PO4)7:Eu2+,Mn2+ phosphors were prepared by the solid‐state reaction method in a reducing atmosphere. Its crystal structure and phase composition were identified by high‐resolution transmission electron microscopy, selected area electronic diffraction, X‐ray photoelectron spectroscopy, and X‐ray powder diffraction Rietveld refinement, and it was found to be trigonal, belonging to R‐3c(161) space group. The luminescence properties of Eu2+ singly doped and Eu2+/Mn2+ codoped Ca8ZnLa(PO4)7 phosphors were revealed in detail. Ca8ZnLa(PO4)7:Eu2+ is excitable over a broad range from 200 to 450 nm with a prominent green emitting. With varied Eu2+/Mn2+ ratios, fine‐tune emission under 365 nm excitation can be achieved from green (0.221, 0.468) to magenta (0.391, 0.276), especially the warm white light (0.392, 0.352), and CCT 3500 K can be obtained by the process of energy transfer between Eu2+ and Mn2+. The ET mechanism in this system is managed via the dipole‐dipole interaction with the maximum energy‐transfer efficiency 82.8% based on the decay lifetime data. These results suggest that as‐prepared phosphors can serve as promising candidates of UV‐pumped w‐LEDs.  相似文献   

12.
The development of novel single-component white-emitting phosphors with high thermal stability is essential for improving the illumination quality of white light-emitting diodes. In this work, we synthesized a series of Ce3+, Tb3+, Mn2+ single- and multiple-doped Ca9La(PO4)7 (CLPO) phosphors with β-Ca3(PO4)2-type structure by the simple high-temperature solid-state reaction. The crystallization behavior, crystal structure, surface morphology, photoluminescence performance, decay lifetime and thermal stability were systematically investigated. The PL spectra and decay curves have evidenced the efficient energy transfer from Ce3+ to Tb3+ and from Ce3+ to Mn2+ in the CLPO host, and corresponding energy transfer efficiency reaches 41.8% and 54.1%, respectively. The energy transfer process of Ce3+→Tb3+ and Ce3+→Mn2+ can be deduced to the resonant type via dipole-dipole and dipole-quadrupole interaction mechanism, and corresponding critical distance were determined to be 12.23 and 14.4 Å, respectively. Based on the efficient energy transfer, the white light emission can be successfully achieved in the single-component CLPO:0.15Ce3+, 0.10Tb3+, 0.04Mn2+ phosphor, which owns CIE chromaticity coordinates of (0.3245, 0.3347), CCT of 5878 K, internal and external quantum efficiency of 84.51% and 69.32%. Especially, compared with the emission intensity at 25 °C, it still remains 98.5% at 150 °C and 92.0% at 300 °C. Based on these results, the single-component white light emission phosphor CLPO:0.15Ce3+, 0.10Tb3+, 0.04Mn2+ is a potential candidate for UV-converted white LEDs.  相似文献   

13.
This work presents the ultraviolet–visible spectroscopic properties of Ba3Y2(BO3)4:Ce3+,Tb3+ phosphors prepared by a high‐temperature solid‐state reaction. Under ultraviolet light excitation, tunable emission from the blue to yellowish‐green region was obtained by changing the doping concentration of Tb3+ when the content of Ce3+ is fixed. The efficient energy transfer process between Ce3+ and Tb3+ ions was observed and confirmed in terms of corresponding excitation and emission spectra. In addition, the energy transfer mechanism between Ce3+ and Tb3+ was proved to be dipole–dipole interaction in Ba3Y2(BO3)4:Ce3+,Tb3+ phosphor. By utilizing the principle of energy transfer and appropriate tuning of Ce3+/Tb3+ contents, Ba3Y(BO3)4:Ce3+,Tb3+ phosphors can have potential application as an UV‐convertible phosphor for near‐UV excited white light‐emitting diodes.  相似文献   

14.
A series of Ce3+‐ and Mn2+‐(co‐)activated SrAl2Si2O8 phosphors have been prepared at 1350°C under a reducing atmosphere and their photoluminescence properties have been studied as a function of the (co‐)dopant ions concentrations. We have discovered that energy transfer (ET) not only from Ce3+ to Mn2+ but also from “defects” to Mn2+ by the facts that there is existing significant overlap between the emission spectrum of Ce3+ (“defects”) and the excitation spectrum of Mn2+. The source of the “defects” in the host lattice is originated from the different charge substitution between Ce3+ and Sr2+. By adopting the principle of ET, the material SrAl2Si2O8: Ce, Mn can act as a phosphor for white‐light ultraviolet light‐emitting diodes (UV‐LEDs) by tuning of the dopants contents.  相似文献   

15.
A novel Y3?xSi6N11: xCe3+ yellow phosphor was synthesized using the carbothermal reduction and nitridition method at 1550°C for 16 h in this letter. Photoluminescence spectra indicated that the phosphor showed broad excitation spectrum and had strong absorption in range of 350–450 nm. It also gave a broad emission band (Full width at half maximum = 153 nm) centered at 575 nm under 425‐nm excitation. With increasing Ce3+ concentration, the strongest emission intensity was obtained at 5 mol% Ce3+ doping amount and a systematic redshift was observed as the Ce3+ concentration increased. The results indicate that this novel yellow phosphor is a promising candidate for using in blue‐chip‐excited white light–emitting diodes (LEDs).  相似文献   

16.
Novel Dy3+ and Ce3+ doped Si–B–Na–Sr (SBNS) glasses were synthesized by melt‐quenching technique. Excited by 327 nm, the 0.5Dy3+‐and 0.5Ce3+‐doped SBNS exhibits white emission with Commission Internationale de L'Eclairage coordinates of (0.308, 0.280). Basic optical characterizations have been performed by measuring the absorption and emission spectra and calculating Judd–Ofelt intensity parameters, radiative probability, luminescence branching ratio, cross sections, and effective bandwidth. The Judd–Ofelt parameters Ω2, Ω4, and Ω6 indicate a high asymmetrical environment and covalent environment in the optical glass. The emission color of Ce3+ and Dy3+ codoped transparent glass can be tuned from blue to white through energy transfer from Ce3+ to Dy3+ ions. The resulting glass may have potential application in white‐light‐emitting source.  相似文献   

17.
The Eu2+, M‐codoped(= Ce3+, Mn2+) phosphor powders were prepared by a solid‐state reaction. The addition of Ce3+ in the Eu2+ sites in partially nitridated bredigite‐structure phosphor(CMSN) remarkably enhances the luminescent intensity by ~180% through sensitized luminescence. Dual band emission was observed for Eu, Mn‐codoped CMSN through energy transfer from Eu2+ to Mn2+. Ce3+–Eu2+ and Eu2+–Mn2+ energy‐transfer mechanism was investigated through decay profile analysis using Inokuti–Hirayama model and energy‐transfer parameters are determined. Interaction mechanism was identified as dipole–dipole interaction. In addition, phosphor in glass plates was prepared using the phosphor and its feasibility in white LED application was studied and is presented.  相似文献   

18.
A new method for improving color rendering index (CRI) and low correlated color temperature (CCT) in high‐power white‐light‐emitting diodes (WLEDs) is proposed. We used a configuration of phosphor‐in‐glass (PIG) and studied light output changes with the increment in concentration of yellow‐emitting Y3Al5O12:Ce3+ (YAG:Ce3+) phosphor. The PIG was coupled on the top of blue‐light‐emitting diodes (LED) chip (465 nm). To compensate the lack of red emission in the phosphor, Eu3+‐doped tellurium glass with different europium content was employed as a red emitter. The suitable contents of YAG:Ce3+ and Eu3+ were 7.5 weight percent (wt%) and 3 mol percent (mol%), respectively. The CRI value went from 72 to 82, whereas the CCT was reduced from 24 933 to 6434 K. The proposed structure can improve CCT as well as CRI of WLEDs just by placing a glass on top.  相似文献   

19.
During pursuing high color rendering index for full-color-emitting phosphor, low quantum efficiency (QE) is usually accompanying. We intend to elevate the luminescence efficiency when realizing a solar-like spectra distribution, by constructing apatite structure oxynitride, inheriting high covalence and rigidity from oxynitride, and suitable multiple cation sites from oxyapatite compounds. Full-color-emitting apatite structure oxynitride phosphor (Mg,Y)5Si3(O,N)13:Ce3+,Mn2+ has been prepared, and the crystal sites’ occupancies of activators in this host were favorable for white emission. (Mg,Y)5Si3(O,N)13:Ce3+,Mn2+ phosphor shows whole visible light with emission wavelength ranging from 370 to 750 nm, matching the spectra of sunlight quite well. The fabricated white light-emitting diode lamp demonstrated the distinctive overall performance of QE and chromaticity properties (Ra and R9). Furthermore, correlated color temperature is tunable from cool nature to warm white. The obtained lamp possesses the feature of less blue light hazard and high saturation of red degree, compared with the commercial YAG-based lamp.  相似文献   

20.
Y2/3Cu3Ti4O12 (YCTO) ceramics were successfully synthesized by sol–gel method (SG) and solid‐state method (SS), respectively. The optimized processing parameters for the syntheses of precursor powders by sol–gel process were determined as follows: the Ti(OC4H9)4 concentration was 0.50 mol/L, the CH3COOH volume was 8 mL, and the volume percentage of H2O was 11.2%. Particularly, on the basis of XRD and TG‐DSC analyses, the phase formation temperature of YCTO‐SG was at least 100°C lower than that of YCTO‐SS. YCTO‐SG ceramics sintered at 1060°C for 25 h showed fine‐grained microstructure, and higher dielectric constant (ε ≈ 5.24 × 104) at 1 kHz compared to YCTO‐SS ceramics (ε ≈ 0.93 × 104). The higher dielectric constant of the YCTO‐SG ceramics was attributed to the grain size effect. Furthermore, the YCTO‐SG ceramics showed a distinct high‐temperature (>300°C) relaxor‐like behavior. According to the calculated activation energy value, the single ionization of oxygen vacancies was responsible for the conduction and dielectric anomaly behaviors of YCTO‐SG ceramics.  相似文献   

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