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1.
《Ceramics International》2020,46(5):6154-6159
Ca2YZr2Al3O12:Bi3+,Eu3+ phosphors were elaborated by a traditional solid-state reaction method. The luminescence of Ca2YZr2Al3O12:Bi3+ samples, energy transfer from Bi3+ to Eu3+, and the temperature sensing properties of Ca2YZr2Al3O12:Bi3+,Eu3+ samples have been systematically researched. Under the excitation of ultraviolet light, Bi3+ single doped phosphors give 313 and 392 nm emission bands, which origin from the substitutions of Bi3+ instead of Ca2+ and Y3+ sites, respectively. And the color-adjustable emission from blue to red were observed by increasing Eu3+ content in Ca2YZr2Al3O12:Bi3+,Eu3+ samples. Relying on different temperature dependent variation tendency, the fluorescence intensity ratio (FIR) values present outstanding temperature sensing properties. The absolute and relative sensitivity can be up to 0.826 %K-1 and 0.664 %K-1, respectively. All above results suggest that Ca2YZr2Al3O12:Bi3+,Eu3+ phosphor is a potential alternative for optical thermometer. 相似文献
2.
《Ceramics International》2023,49(7):10961-10975
In this study, the phosphorescence properties of Eu3+ and Er3+ co-doped yttria stabilized zirconia (YSZ: Eu3+, Er3+) as a function of oxygen partial pressure and temperature are investigated to explore the possibility of using this phosphor for pressure and temperature measurements at elevated temperature (up to 600 °C). The YSZ: Eu3+, Er3+ phosphors have a fixed Eu3+ concentration (1 mol%) and a varied Er3+ concentration (0.5–5 mol%). The phosphorescence intensity and lifetime of Eu3+ bands are sensitive to both oxygen partial pressure and temperature when temperature exceeds 400 °C. This oxygen/pressure sensitivity is related to the oxygen vacancy-induced non-radiative decay through charge transfer state (CTS), and is inversely correlated with Er3+ concentration. In contrast, the phosphorescence intensity and lifetime of Er3+ bands are temperature-sensitive but oxygen-insensitive, which is related to the dominant oxygen-independent 4S3/2 → 2H11/2 transition. Accordingly, two measurement strategies are proposed including an intensity ratio method and a lifetime method. The intensity ratio of the oxygen-sensitive Eu3+ bands and the oxygen-insensitive Er3+ reference bands is capable of 2D pressure measurement using a dual-camera system. But temperature-induced errors exist due to the temperature-sensitivity of intensity ratio. Simultaneous pressure and temperature measurements (point by point) can be achieved utilizing two PMTs that record the lifetimes of Eu3+ and Er3+, respectively. This method can resolve the issue of temperature sensitivity of Eu3+ and accurately correct the temperature-induced errors. The YSZ: Eu, Er phosphors show great potential for applications in high-temperature environment where the existing organic PSPs and TSPs cannot survive. 相似文献
3.
Junhang Tian Weidong Zhuang Ronghui Liu Ligen Wang Yuanhong Liu Chunpei Yan Guantong Chen Huibing Xu Mingyue Chen Ze Jiang Xia Zhang 《Journal of the American Ceramic Society》2019,102(12):7336-7346
Enhancing thermal quenching characteristic of phosphor for use in high power white-light-emitting diodes (wLEDs) is a significant materials challenge. To achieve this goal, a series of red-emitting carbidonitride phosphors Ca0.992AlSiN3 − 4/3xCx:0.008Eu2+ have been synthesized by high-temperature solid-state reaction method. Crystal structure, luminescence properties, and thermal quenching process are investigated. The location of carbon in the lattice is proved by the Raman spectra. The preferential crystallographic site of carbon is validated by the first-principles density functional theory calculations combining the Rietveld refinement. With carbon doping from x = 0 to x = 0.24, the emission spectra are blue-shifted from 656.8 to 650.2 nm, and the fitted lifetime of Eu2+ decreases from 775.3 to 721.7 ns. Replacing nitrogen by carbon enhances thermal quenching characteristic by 8.9% at 300°C. Carbon doping enlarges the thermal ionization energy barriers (EdC) which is calculated at great length, and suppresses thermal ionization process. A wLED fabricated by the combination of a blue chip with the as-synthesized red phosphor and LuAG: Ce3+ green phosphor shows a high color rendering indexes (Ra = 95.9 and R9 = 92). The promising application of Ca0.992AlSiN3 − 4/3xCx:0.008Eu2+ phosphor for wLEDs is proved by all results above. 相似文献
4.
《Ceramics International》2017,43(18):16323-16330
The tricolor-emitting MgY4Si3O13: Ce3+, Tb3+, Eu3+ phosphors for ultraviolet-LED have been prepared via a high-temperature solid-state method. X-ray diffraction, photoluminescence emission, excitation spectra and fluorescence lifetime were utilized to characterize the structure and the properties of synthesized samples. Two different lattice sites for Ce3+ are occupied from the host structure and the normalized PL and PLE spectra. The emissions of single-doped Ce3+/Tb3+/Eu3+ are located in blue, green and red region, respectively. The energy transfer from Ce3+ to Tb3+ and from Tb3+ to Eu3+ has been validated by spectra and decay curves and the energy transfer mode from Tb3+ to Eu3+ was calculated to be electric dipole-dipole interactions. By adjusting the content of Tb3+ and Eu3+ in MgY4Si3O13: Ce3+, Tb3+, Eu3+, the CIE coordinates can be changed from blue to green and eventually generate white light under UV excitation. All the results indicate that the MgY4Si3O13: Ce3+, Tb3+, Eu3+ phosphors are potential candidates in the application of UV-WLEDs. 相似文献
5.
Ye Tong YiHang Chen SunYueZi Chen RongFei Wei LiPing Chen Hai Guo 《Ceramics International》2021,47(9):12320-12326
Herein, a series of novel Na2GdMg2(VO4)3:Eu3+ (NGMVO:Eu3+) red phosphors were elaborated by conventional solid-state reaction process. Their structural features, luminescent properties, energy transfer were researched at length. XRD patterns indicate that NGMVO:Eu3+ crystallized in single cubic garnet structure. Under the excitation of near ultraviolet light at 356 nm, the emission spectra of NGMVO host could be divided in two parts that resulted from 3T2 → 1A1 and 3T1 → 1A1 transitions of VO43?. While NGMVO:Eu3+ phosphors show intense sharp red emission peaks including 590, 610, 652 and 706 nm that originated from 5D0 → 7FJ (J = 1–4) transitions of Eu3+, respectively. The optimal concentration of Eu3+ is 0.7. Importantly, NGMVO:0.7Eu3+ sample presents high energy transfer efficiency (89 %) and high external quantum efficiency (48.3 %). Besides, its emission intensity remains 79 % at 420 K compared with that at 300 K, proving the good thermal stability of phosphors. All above results suggest that NGMVO:Eu3+ red phosphors have latent applications in white light emitting diodes. 相似文献
6.
Zheng Lu Dashuai Sun Zeyu Lyu Sida Shen Pengcheng Luo Shuai Wei Luhui Zhou Hongpeng You 《Journal of the American Ceramic Society》2023,106(11):6617-6629
A series of LaCaGaO4:xBi3+,yEu3+ (x = 0.002–0.04, y = 0.02–0.45) phosphors with adjustable emission colors were synthesized by high-temperature solid-state reaction. The samples were identified as pure phases by X-ray diffraction and Rietveld refinement, and the crystal structures were analyzed in detail. The LaCaGaO4:xBi3+ phosphor shows an intense blue emission under near-ultraviolet excitation, originating from the 3P1 → 1S0 transition. The spectrum analysis reveals that the Bi3+ ions occupy two luminescence centers in the LaCaGaO4 host and that energy transfer can occur. A model of the energy transfer between the Bi3+ and Eu3+ ions was also created and studied in detail. As the Eu3+-concentration increased, the emission color of the LaCaGaO4:0.005Bi3+,yEu3+ phosphor changed from blue to pink to red. In addition, the fluorescence lifetime, quantum yield, thermal stability, and other properties of the phosphors were characterized and analyzed. Finally, two white light-emitting diode devices with Ra values of 96.6 and 95 and correlated color temperatures of 4578 and 3324 K were fabricated, indicating the potential of phosphors for warm white lighting applications. 相似文献
7.
《Ceramics International》2019,45(11):13832-13837
In this study, Eu3+-doped LiCa2Mg2V3O12 (LCMVO) phosphors with multicolor luminescent property were prepared by the solid phase reaction. Their structure, morphology and luminescent property were studied systematically by X-ray diffraction, scanning electron microscope and photoluminescence spectra. The LCMVO phosphors showed pure cubic crystal structure with space group () and irregular spherical morphology. The excitation spectra showed a strong absorption to ultraviolet light. Under the excitation wavelength at 360 nm, they exhibited a cyan emission with a luminescence center at 520 nm. When Eu3+ ions were doped into LCMVO system, the Eu3+ characteristic emissions were also observed and the emission colors were tuned from cyan to orange via adjusting Eu3+ ion concentration. Further, electric dipole-quadrupole interaction and luminescence decay curves were adopted to explain the energy transfer from (VO4)3- to Eu3+. The emission spectra of as-obtained phosphors at different temperature were measured to evaluate their thermal stability. The quantum efficiency values were measured to be 42.5% for LCMVO host and 38.6% for LCMVO: 0.01Eu3+ sample. The final prepared LED lamp showed easeful warm white light with suitable Ra of 89 and CCT of 3847 K, respectively. These results suggest LCMVO phosphors may be applied in near ultraviolet chip-excited white light-emitting diodes. 相似文献
8.
《Ceramics International》2023,49(7):10273-10279
The photoluminescence behavior of inorganic phosphors is generally influenced by thermal stability, which determines the luminescence efficiency of the corresponding devices. Here, a series of Eu2+, Mn2+ co-doped LiAl5O8 blue-green-emitting phosphors with thermal robust are successfully fabricated. The concentration-dependent emission spectra and the decay curves of the as-obtained LiAl5O8: Eu2+, Mn2+ samples manifest the occurrence of the energy transfer from Eu2+ to Mn2+ ions via dipole-dipole interaction, and the corresponding emitted colors are gradually modulated from blue to green under the excitation of 310 nm. Moreover, the zero-thermal-quenching luminescence is observed when the operation temperature is up to 423 K, which is attributed to the energy release from the trapping centers to emitting centers (Eu2+ and Mn2+) at high temperature. Furthermore, a warm white light-emitting diodes (WLEDs) device with correlated color temperature of 5061 K, a color rendering index of 80.6 and long-term stability is fabricated by combining UV LED chip (λex = 310 nm), as-obtained LiAl5O8: Eu2+, Mn2+ phosphor, commercially available red phosphor and green phosphor. These results prove the potential application of the as-obtained LiAl5O8: Eu2+, Mn2+ phosphor for UV-pumped WLEDs devices. 相似文献
9.
《Ceramics International》2023,49(10):15402-15412
A series of Ca2GdNbO6: xSm3+ (0.01 ≤ x ≤ 0.15) and Ca2GdNbO6: 0.03Sm3+, yEu3+ (0.05 ≤ y ≤ 0.3) phosphors were synthesized by the traditional solid-state sintering process. XRD and the corresponding refinement results indicate that both Sm3+ and Eu3+ ions are doped successfully into the lattice of Ca2GdNbO6. The micro-morphology shows that the elements of Ca2GdNbO6: 0.03Sm3+, 0.2Eu3+ phosphor are evenly distributed in the sample, and the particle size is about 2 μm. The optical properties and fluorescence lifetime of Ca2GdNbO6: 0.03Sm3+, Eu3+ phosphors were detailedly studied. The emission peak at 5D0→7F2 (614 nm) is the strongest and emits red light under 406 nm excitation. The increase of Eu3+ concentration causes the energy transfers from Sm3+ to Eu3+ ions, and the transfer efficiency reaches 28.6%. Ca2GdNbO6: 0.03Sm3+, 0.2Eu3+ phosphor has a quantum yield of about 82.7%, and thermal quenching activation energy is of 0.312 eV. The color coordinate (0.646, 0.352) of Ca2GdNbO6: 0.03Sm3+, 0.2Eu3+ phosphors is located in the red area. The LED device fabricated based on the above phosphor emit bright white light, and CCT = 5400 K, Ra = 92.8. The results present that Ca2GdNbO6: 0.03Sm3+, Eu3+ phosphors potentially find use in the future. 相似文献
10.
White light emission from novel host-sensitized single-phase Y2WO6: Ln3+ (Ln3+=Eu3+, Dy3+) phosphors
《Ceramics International》2016,42(12):13841-13848
A series of Eu3+- or Dy3+-doped and Eu3+/Dy3+ co-doped Y2WO6 in pure phase was synthesized via high-temperature solid-state reaction. X-ray diffraction, diffuse reflection spectra, photoluminescence excitation and emission spectra, the CIE chromaticity coordinates and temperature-dependent emission spectra were exploited to investigate the phosphors. Upon UV excitation at 310 nm, efficient energy transfer from the host Y2WO6 to dopant ions in Eu3+ or Dy3+ single-doped samples was demonstrated and those phosphors were suitable for the UV LED excitation. The intense red emission was observed in Y2WO6: Eu3+, and blue and yellow ones were observed in Y2WO6: Dy3+. Concentration quenching in Y2WO6: Dy3+ phosphors could be attributed to the electric dipole-dipole interaction. In Eu3+/Dy3+ co-doped Y2WO6 phosphors energy transfer process only took place from the host to Eu3+/Dy3+ ions and warm white-light emission can be obtained by adjusting the dopant concentrations. The temperature-dependent luminescence indicated Eu3+/Dy3+ co-doped Y2WO6 was thermally stable. Our overall results suggested that Y2WO6: Ln3+ (Ln3+=Eu3+, Dy3+) as warm white-light emitting host-sensitized phosphor might be potentially applied in WLEDs. 相似文献
11.
《Ceramics International》2017,43(15):12044-12056
Perovskite type titanate phosphors Sr0.97−xDy0.03LixTi1−xNbxO3, Sr0.9−xDyxLi0.1Ti0.9Nb0.1O3 and Sr0.87−yDy0.03EuyLi0.1Ti0.9Nb0.1O3 were prepared by conventional solid state method. Herein, white light emission from Sr0.9−xDyxLi0.1Ti0.9Nb0.1O3 phosphors and the lowering of its color temperature through codoping with Eu3+ ions are reported. Raman measurements have shown that the incorporation of dopants alters the vibrational properties of these phosphors significantly, indicating the reduction of the local symmetry in the crystal lattice. The addition of LiNbO3 in SrTiO3:Dy3+ phosphor enhances the luminescence intensity and the yellow to blue ratio resulting in emission of high quality white light with color coordinates corresponding to that of standard white. Life time measurements and data fits of Sr0.9−xDyxLi0.1Ti0.9Nb0.1O3 phosphors revealed the biexponential behaviour of luminescence decay profiles. From Judd-Ofelt analysis it is found that the intensity parameter Ω2 increases with Dy3+ concentration and a quantum efficiency of 90.4% was obtained for optimum concentration. In the case of Dy3+ and Eu3+ codoped phosphors, the color coordinates are found to be sensitive to the Eu3+ concentration and the highest energy transfer efficiency of 92% was obtained for the phosphor doped with 10 mol% Eu3+. The emission color changes from cold white to reddish orange when the wavelength of excitation alters from 452 to 388 nm, since the energy transfer mechanism alone take place under 452 nm excitation and both direct absorption and the energy transfer mechanism occurs under 388 nm excitation. 相似文献
12.
Dayu Huang Yi Wei Peipei Dang Xiao Xiao Hongzhou Lian Jun Lin 《Journal of the American Ceramic Society》2020,103(5):3273-3285
LaScO3:xBi3+,yTb3+,zEu3+ (x = 0 − 0.04, y = 0 − 0.05, z = 0 − 0.05) phosphors were prepared via high-temperature solid-state reaction. Phase identification and crystal structures of the LaScO3:xBi3+,yTb3+,zEu3+ phosphors were investigated by X-ray diffraction (XRD). Crystal structure of phosphors was analyzed by Rietveld refinement and transmission electron microscopy (TEM). The luminescent performance of these trichromatic phosphors is investigated by diffuse reflection spectra and photoluminescence. The phenomenon of energy transfer from Bi3+ and Tb3+ to Eu3+ in LaScO3:xBi3+,yTb3+,zEu3+ phosphors was investigated. By changing the ratio of x, y, and z, trichromatic can be obtained in the LaScO3 host, including red, green, and blue emission with peak centered at 613, 544, and 428 nm, respectively. Therefore, two kinds of white light-emitting phosphors were obtained, LaScO3:0.02Bi3+,0.05Tb3+,zEu3+ and LaScO3:0.02Bi3+,0.03Eu3+,yTb3+. The energy transfer was characterized by decay times of the LaScO3:xBi3+, yTb3+, zEu3+ phosphors. Moreover absolute internal QY and CIE chromatic coordinates are shown. The potential optical thermometry application of LaScO3:Bi3+,Eu3+ was based on the temperature sensitivity of the fluorescence intensity ratio (FIR). The maximum Sa and Sr are 0.118 K−1 (at 473.15 K) and 0.795% K−1 (at 448.15 K), respectively. Hence, the LaScO3:Bi3+,Eu3+ phosphor is a good material for optical temperature sensing. 相似文献
13.
Energy transfer realizes efficient NIR emitting Ca2ScTaO6:Cr3+, Yb3+ perovskite-structured phosphors
《Ceramics International》2023,49(10):15717-15725
Stable and efficient broadband near-infrared (NIR) emitting phosphors are vital for the next-generation NIR sources. However, it still remains challenging to construct such phosphors, particularly those with a NIR-II window. In this work, using the Cr3+-Yb3+ energy transfer (ET) strategy, the as-synthesized Ca2ScTaO6:Cr3+, Yb3+ phosphor retains 86.2% of the initial luminescence intensity of Yb3+ at 373 K with characteristic emissions of both activators ranging from 700 nm to 1200 nm. The occupation of Cr3+ into both Ta5+ and Sc3+ sites is confirmed by X-ray diffraction, time-resolved emission spectrum, and crystal structure. The efficient ET from Cr3+ to Yb3+ is revealed by the diffuse reflection spectrum, steady-state and transient fluorescence. As a result, it contributes to the excellent performance of the phosphor. Based on the optimized phosphor, a NIR light-emitting diode is fabricated and demonstrated its advantage in imaging and potential application in information encryption. The result highlights ET as a robust strategy to construct efficient NIR phosphor. 相似文献
14.
《Ceramics International》2022,48(9):12281-12290
Following the rapid growth of lightning technology, the development of red-emitting phosphors is effective for improving color temperature and color rendering index for w-LEDs devices. Herein, a single phased garnet phosphor with cation and polyhedron substitution modification was firstly prepared. For Mg3Gd2Ge3O12: Bi3+, Eu3+, the intensity has been remarkably improved by about 16% compared to the one without Bi3+ sensitization. The energy transfer mechanism is identified in this work. Based on cation and polyhedron substitution strategies, novel phosphors with different compositions were obtained and further modified the PL properties. With Lu3+ substitution, the bond lengths between Bi3+ ion and anion ligands are decreased and the site symmetry has been strengthened, which leads to a 21 nm blue shift when Lu3+ totally replaced Gd3+ ions. In addition, Lu3+ and [SiO4] substitution strategies both effectively increased symmetric rigid structure, which leads to a significant improvement in thermal stability, indicating the samples own great potential in optical applications This work provides a new insight to synthesis red-emitting phosphors for warm white-LEDs. 相似文献
15.
《Ceramics International》2017,43(13):10239-10246
Luminescent LaF3:Dy3+ and LaF3:Dy3+ co-doped with Ce3+ have been successfully synthesized separately via co-precipitation method. Different ratios of ethylene glycol(EG)/water have been used for the synthesis of LaF3:Dy3+ whereas LaF3:Dy3+ co-doped with Ce3+ have been prepared only in ethylene glycol(EG) medium. The synthesized products have been characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra‐red (FT-IR) and photoluminescence spectroscopy. XRD results show all the samples prepared to be well crystallized in a pure hexagonal structure with no impurity phases. Photoluminescence, lifetime decay and energy transfer efficiency studies indicate the existence of an energy transfer between the Ce3+ and Dy3+ ions, which increases with increase of Dy3+ ions concentration. LaF3:Dy3+ nanophosphor prepared in EG:water mixture(1:1) showed the highest luminescence intensity when compared with those prepared in EG or water alone. This enhancement in luminescence (when using EG-water mixture) might be related to the increase in crystallinity/particle size as well as to the decrease in agglomeration of particles in the corresponding solvent mixture medium. 相似文献
16.
Xin Wang Xiangping Li Rensheng Shen Sai Xu Xizhen Zhang Lihong Cheng Jiashi Sun Jinsu Zhang Baojiu Chen 《Journal of the American Ceramic Society》2020,103(2):1037-1045
A series of YNbO4: Sm3+ powder phosphors with different doping concentrations were synthesized by a traditional high-temperature solid-state reaction method. The crystal structure of the obtained samples was characterized by means of X-ray diffraction. Concentration quenching, energy-transfer mechanism, and luminescence thermal stability of YNbO4: Sm3+ samples were studied through the fluorescence spectra and decays. It was concluded that electric dipole-dipole interaction was the dominant energy-transfer mechanism between Sm3+ ions according to both Van Uitert's model and Dexter's model. Using the Arrhenius model, crossover process was proven to be responsible for the luminescence thermal quenching of Sm3+. Moreover, a novel approach for evaluating the optical transition properties of Sm3+ ion in YNbO4 powders using the diffuse-diffraction spectrum and fluorescence decay was examined in the framework of Judd-Ofelt (J-O) theory. It was confirmed that the J-O parameters Ωλ (λ = 2, 4, 6) of Sm3+ in YNbO4 powder were reliable by comparing the radiation transition rate with the measured emission results. 相似文献
17.
YongTao An Christophe Labbé Larysa Khomenkova Magali Morales Xavier Portier Fabrice Gourbilleau 《Nanoscale research letters》2013,8(1):43
In this study, we report on the evolution of the microstructure and photoluminescence properties of Pr3+-doped hafnium silicate thin films as a function of annealing temperature (TA). The composition and microstructure of the films were characterized by means of Rutherford backscattering spectrometry, spectroscopic ellipsometry, Fourier transform infrared absorption, and X-ray diffraction, while the emission properties have been studied by means of photoluminescence (PL) and PL excitation (PLE) spectroscopies. It was observed that a post-annealing treatment favors the phase separation in hafnium silicate matrix being more evident at 950°C. The HfO2 phase demonstrates a pronounced crystallization in tetragonal phase upon 950°C annealing. Pr3+ emission appeared at TA = 950°C, and the highest efficiency of Pr3+ ion emission was detected upon a thermal treatment at 1,000°C. Analysis of the PLE spectra reveals an efficient energy transfer from matrix defects towards Pr3+ ions. It is considered that oxygen vacancies act as effective Pr3+ sensitizer. Finally, a PL study of undoped HfO2 and HfSiOx matrices is performed to evidence the energy transfer. 相似文献
18.
《Ceramics International》2023,49(8):12012-12020
Lanthanide (Ln3+) ions doped upconversion (UC) nanosheets have attracted tremendous attention such as displays, sensing, bioimaging and lasers etc, which was benefitting from the intriguing optical characters of Ln3+. However, the field of UC nanosheets has been hindered by low UC conversion efficiencies associate with nonradiative relation (NR) occurring by defect, the existence and influence of defects still cannot be eliminated completely. In this work, we design introduce the impurity energy level by doping Er3+in Bi3O4Br:Er3+ nanocrystal materials, which was closed with the intermediate band (IB) formed by oxygen vacancies defects. The density functional theory calculations confirm the IB energy level was closed with the intermediate excited states of Er3+, which provided the potential to tailored the ground state carriers transition from matrix semiconductor to Er3+ and thus tool to counteract the effect of NR and even enhance the UC luminescence performance. The photo-current results evidenced that the photocarrier success transition from IB to Er3+ intermediate excited states energy level leads to a sharp decrease in the surface carrier, on the contrary, the electron population on the excited state energy level of Er3+ have increased. As a result, compared with unmodified sample the UC emission intensity under excited by 980 nm of green and red is enhanced by 7 and 4 times respectively. This work paves the way to design efficient UC nanosheets through by energy transfer (ET) combine matrix semiconductor with RE and greatly enriches the understanding about the ET behavior of RE. 相似文献
19.
A Princy E Annie Rathnakumari S Masilla Moses Kennedy 《Journal of the American Ceramic Society》2023,106(9):5364-5380
A novel vanadate host Ca2LiMg2V3O12 (CLMV) and the Eu3+-doped samples were synthesized via a solid-state reaction method. The phase formation and the morphological analysis were studied in detail. The Rietveld refinement result shows that the host belongs to cubic space group Ia-3d (230) with lattice parameter, a = 12.3948 Å, V = 1904.23 Å3, and Z = 8. The diffuse reflectance spectroscopy measurement estimated the bandgap of the host and the CLMV:0.05Eu3+ phosphors. The host exhibits a broad absorption band (peak at 345 nm) ranging from 240 to 380 nm, which is attributed to the charge transfer in the O2−–V5+ complex. Under near UV excitation (λexc = 345 nm), the host gives a broad emission band covering the visible region from 400 to 730 nm and the emission is in the bluish–green region of the CIE diagram. When the host is doped with the Eu3+ ions and excited at 345 nm, the emission spectrum depicts the superimposition of the characteristic emission bands (red emission) of the Eu3+ ions corresponding to the f–f transitions over the broad emission band of the host. The calculated color coordinates (9600 to 2280 K) demonstrated the color tuning ability of the phosphor as the dopant concentration is increased in the host. This is because the VO43− group plays the sensitiser role and partially transfers energy with the Eu3+ ions. When the same set of phosphors were excited at the dominant characteristic excitation band (λexc = 394 nm) of the Eu3+, the characteristic emission bands of the Eu3+ in the orange–red region were observed. As the electric dipole transition of the Eu3+ was found to be dominant, the prepared phosphors possessed high color purity (CP). The energy transfer mechanism and the lifetime values were also presented. The temperature-dependent PL studies showed good thermal stability of the optimum sample. Various radiative transition properties were analyzed by the Judd–Ofelt theory. The photometric results reveal the color tuning ability and CP of the CLMV:xEu3+ phosphors. 相似文献
20.
《Ceramics International》2022,48(13):18793-18802
The luminescence center energy transfer, crystal field strength, and covalency are limited by the crystal structure of the host and subsequently affect the luminescence efficiency, color, and intensity. Here, we report an excellent red phosphor BaLaLiWO6:0.40Eu3+ and the dependence between symmetry and luminous performance. A model for changing symmetry is drawn by analyzing the Coulomb potential and structure for the application of a double-perovskite phosphor BLLWO: Dy3+, Eu3+ in white light LEDs. The addition of Dy3+/Eu3+ makes the W-O bond formed by the B-site and oxygen ion longer and the Li-O bond shorter, and the difference between the eight octahedral around the A-site is reduced, increasing the symmetry of the A-site. Local symmetry was successfully modulated by changing the Eu3+ concentration to control the Y/B ratio of Dy3+ and the R/O ratio of Eu3+ and smoothly achieved (0.382, 0.373) warm white light color coordinate. The phosphor has excellent thermal stability and still has 92.3% intensity at 475 K. The above results show that the wavelength composition of the luminescence is tunable by changing the symmetry of the environment in which the doped ions are located. It applies to single hosts for the regulation of white light emission. 相似文献