查找使用阿拉丁产品的科研文献

Phase evolution, structure, and up-/down-conversion luminescence of Li6CaLa2Nb2O12:Yb3+/RE3+ phosphors (RE = Ho, Er, Tm)

Panpan Du,Jing Ma,Qi Zhu,Ji-Guang Li

Garnet-type Li 6 Ca(La 0.97 Yb 0.02 RE 0.01 ) 2 Nb 2 O 12 (RE = Ho, Er, Tm) new phosphors were successfully synthesized via solid reaction at 900°C for 5 hours, whose course of phase evolution, macroscopic/local crystal structure and up-/down-conversion (UC/DC) photoluminescence were clarified. Mechanistic study and materials characterization were attained via XRD, Rietveld refinement, DTA/TG, electron microscopy (FE-SEM/TEM), and Raman/reflectance/fluorescence spectroscopies. The phosphors were shown to exhibit UC luminescence dominated by a ~ 553 nm green band ( 5 F 4 / 5 S 2 → 5 I 8 transition) for Ho 3+ , a ~ 568 nm green band ( 4 S 3/2 → 4 I 15/2 transition) for Er 3+ and a ~ 806 nm near-infrared band ( 3 H 4 → 3 H 6 transition) for Tm 3+ under 978 nm laser excitation, with CIE chromaticity coordinates of around (0.31, 0.68), (0.38, 0.60) and (0.17, 0.24), respectively. Analysis of the pump-power dependence of UC intensity indicated that all the emissions involve a two-photon mechanism except for the ~ 486 nm blue emission of Tm 3+ ( 1 G 4 → 3 H 6 ), which requires a three-photon process. The DC luminescence of these phosphors is featured by dominant bands at ~ 553 nm for Ho 3+ (green, 5 F 4 / 5 S 2 → 5 I 8 transition), ~568 nm for Er 3+ (green, 4 S 3/2 → 4 I 15/2 transition) and ~ 464 nm for Tm 3+ (blue, 1 D 2 → 3 F 4 transition). The UC and DC properties were also comparatively discussed.

Effects of Re3+ radius on phase composition and thermal sensitivity of Ba4.5Re9Ti18O54 ceramics

Ruifeng Wu,Yafei Liu,Hao Sun,Jianan Xu,Jia Chen,Aimin Chang,Bo Zhang

Tungsten-bronze materials are widely used in the fields of electro-optic, photorefractive, pyroelectric, millimeter-wave, and piezoelectric devices. In particular, tungsten-bronze Ba 4.5 Sm 9 Ti 18 O 54 is believed to be useful for fabricating high-temperature thermistors owing to its semiconductor properties. However, inherent shortcomings such as poor linearity (electrical properties deviate from the Arrhenius equation) and high aging coefficients limit the practical applications of these materials. Incorporating rare-earth ( Re ) ions is an effective means of improving the electrical properties of thermistor materials. In this study, we explore the phase composition and thermosensitive properties of Ba 4.5 Re 9 Ti 18 O 54 (Re = Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu) ceramics with tungsten–bronze structures. The results indicate that the tungsten–bronze phase (Ba 4.5 Re 9 Ti 18 O 54 ) is generated when the radius of the Re 3+ ion exceeds 1.04 Å and the tolerance factor surpasses 0.82. Conversely, a pyrochlore phase (Re 2 Ti 2 O 7 ) accompanied by a monoclinic impurity phase (BaTi 2 O 5 ), is formed. Moreover, all Ba 4.5 Re 9 Ti 18 O 54 ceramics with a tungsten-bronze structure exhibit exceptional linear electrical properties ( R 2 ≥ 999.09‰) and high sensitivity coefficients ( α 1000°C ≥ −0.79%/K). In particular, after aging at 1100°C for 600 h, both the aging coefficient and drift rate of material constant are as low as 5.76% and 1.79%, respectively. These results indicate that Ba 4.5 Re 9 Ti 18 O 54 ceramics are promising for high-temperature and high-accuracy temperature measurements.

Efficient upconversion and downshifting luminescence of CaIn2O4: Yb3+/Tm3+/RE3+ (RE=Er/Ho) phosphor: Temperature sensing performance in the visible and near-infrared range

Hang Liu,Ziyi Zhang,Jian Liu,Kailin Wang,Yuhong Zhang

In this paper, the upconversion(UC) and downshifting(DS) luminescence and thermal sensing performances of the CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ (RE=Er, Ho) phosphors are investigated in detail. The bright UC emission bands from 450 to 900 nm and the DS luminescence bands from 1000 to 1700 nm are obtained under 980 nm excitation. The typical near infrared(NIR) emisson band(∼1550 nm) of Er 3+ ions and the NIR emission band(∼1200 nm) of Ho 3+ ions are gained. The temperature sensing features of CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ (RE=Er, Ho) phosphors are investigated with the luminescence intensity ratio (LIR) technique. The results indicate that the maximum relative sensitivity (S Rmax ) of CaIn 2 O 4: Er 3+ /Tm 3+ /Yb 3+ sample reaches 1.576% K -1 at 313 K, and the S Rmax of CaIn 2 O 4: Ho 3+ /Tm 3+ /Yb 3+ sample reaches 0.797% K -1 at 353 K in UC range. In addition, the higher temperature measuring sensitivities have been obtained in NIR-II region with the DS luminescence of CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ phosphors. The above results indicate that the CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ phosphors show bright emission bands in visible and NIR-II, and higher sensitivity for temperature measurement. The CaIn 2 O 4: RE 3+ /Tm 3+ /Yb 3+ phosphors present great application in optical temperature measurement.

Multicolor luminescence properties of Ln7O6F9: RE3+ (Ln = Y, Lu; RE = Pr, Sm and Eu) nano-rods with bifurcation

Guang-Xin Xiang,Guo-Jun Wang,Zhi-Jun Zhang,He Feng,Jing-Tai Zhao,Jiao Wang,Xin-Yuan Sun,Ri-Hua Mao,Yong Wang

The uniform 1D nano-rods of RE 3+ doped Ln 7 O 6 F 9 ( Ln  = Y and Lu; RE  = Pr, Sm and Eu) were synthesized through a facile two-step hydrothermal method without extra fluorine source followed by post-heat treatment. The phase formation, morphologies, as well as photoluminescence properties of the materials were investigated. The precursor composition was determined to be Ln (OH) 1.69 F 1.31 using the Fourier transform infrared spectrum (FT-IR), thermal gravimetric and differential scanning calorimetry (TG-DSC). The average lengths of Y 7 O 6 F 9 and Lu 7 O 6 F 9 were about 6.8 and 7.9 μm, respectively, with the average width of about 650 nm. It was interesting that the tip of the nano-rods exhibits a straight line and divergent umbrella shaped bifurcation for Y 7 O 6 F 9 and Lu 7 O 6 F 9 , respectively. Upon ultraviolet excitation, Pr 3+ , Sm 3+ and Eu 3+ ions in Ln 7 O 6 F 9 showed blue, orange and red emissions originating from their characteristic f-f transitions. In addition, the 4 f 1 5 d 1  → 4 f 2 band emissions (340–450 nm) as well as typical 4 f 2  → 4 f 2 line emissions (450–700 nm) of Pr 3+ were observed in Pr 3+ -doped Ln 7 O 6 F 9 . For Sm 3+ -doped Ln 7 O 6 F 9 , only the typical f - f transitions of Sm 3+ were observed with the absence of charge transfer (CT) band. However, the broad excitation bands at 255 nm attributing to the charge transfer transition of Eu 3+ (i.e. O 2−  → Eu 3+ CT) were observed in Eu 3+ -doped Ln 7 O 6 F 9 .

Sol-gel auto-combustion synthesis and luminescence properties of GdCaAl3O7: RE3+ (RE=Eu, Tb, Eu@Tb) phosphors for near-ultraviolet light-triggered indoor illumination

Haoran Zhou,Linwen Jiang,Xin Chen,Anhua Wu,Zhuo Tang,Hongbing Chen

The color-tunable GdCaAl 3 O 7 : RE 3+ (RE = Eu, Tb, Eu@Tb) phosphors were synthesized via an ultrafast sol-gel auto-combustion synthesis method. The X-ray diffraction patterns confirmed the forming of GdCaAl 3 O 7 tetragonal phase, and the scanning electron microscopy images indicated that the obtained products presented honeycomb-like structure due to the gas releasing during the auto-combustion process. The luminescent properties, concentration quenching mechanism, energy transfer mechanism, luminescent dynamics, thermal stability and product practicability of GdCaAl 3 O 7 : RE 3+ (RE = Tb, Eu, Eu@Tb) phosphors were investigated systematically. All the GdCaAl 3 O 7 : RE 3+ products presented the characteristic emission of doped RE 3+ . Using GdCaAl 3 O 7 : 50% Tb 3+ @3.0% Eu 3+ as yellow-emitting phosphors in combination with commercial BAM: Eu 2+ blue-emitting phosphors and a NUV chip can successfully package a warm white LED device with high color rendering index (CRI, 86.3) and low correlated color temperature (CCT, 3348 K) that was very suitable for near-ultraviolet light-triggered indoor illumination.

Temperature-dependent law of transition probability associated with main emission states in YVO4:Re3+ (Re3+=Sm3+, Dy3+ and Eu3+)

Changwen Wang,Lixin Peng,Feng Qin,Meng Kou,Yongda Wang,Lingling Xu,Zhiguo Zhang

The understanding of how radiative transition probabilities change with temperature is crucial for comprehending the relationship between fluorescence behavior and temperature. However, although various models have been proposed to explain the patterns of transition probabilities ( A ) with temperature changes, they lack consistency due to their derivation from distinct microscopic perspectives. In this study, the macroscopic law of the temperature-dependent A for the 4 G 5/2 , 4 F 9/2 , and 5 D 0 energy states in YVO 4 :Re 3+ (Re 3+ =Sm 3+ , Dy 3+ and Eu 3+ ) was obtained. Three rare earth ions (Re 3+ ) were identified for each with unique energy level properties conducive to validating the general rules of A . These ions share a common characteristic: in the visible spectrum , their main emissions originate from the radiative transitions from the same higher energy level ( 4 G 5/2 in Sm 3+ , 4 F 9/2 in Dy 3+ , and 5 D 0 in Eu 3+ ) to lower energy levels, respectively. The A of the main emission levels, varying with T , were obtained by fitting the fluorescence decay curves. The exponential law governing non-radiative transitions was revealed after separating the radiative transition rate ( W R ) from A . The macroscopic law of temperature-dependent transition probabilities of 4 G 5/2 , 4 F 9/2 , and 5 D 0 energy states in YVO 4 :Ln 3+ (Ln 3+  = Sm 3+ , Dy 3+ and Eu 3+ ) has been found to follow the Boltzmann distribution . The results indicate that the non-radiative transitions of the main emission levels of the rare-earth ions are processes from the excited state to adjacent lower energy levels. This macroscopic pattern may serve as a foundational rule for understanding the impact of microscopic factors on A .

Structural and spectroscopic features of high color purity red-emitting phosphors Sr19Mg2(PO4)14: Re3+ (Re3+= Eu3+, Sm3+, Pr3+)

Ying Li,Jing Jiang,Qingyi Lv,Bohuai Shao,Chuang Wang,Ge Zhu

The discovery of high color purity red-emitting phosphors is a major challenge for solid-state lighting materials. Benefitting from highly condensed and flexible framework structure of β -Ca 3 (PO 4 ) 2 -type compounds, we have successfully prepared three different kinds of novel high color purity red-emitting phosphors Sr 19 Mg 2 (PO 4 ) 14 : Re 3+ (Re 3+ = Eu 3+ , Sm 3+ , Pr 3+ ) by using traditional sintering method. Rietveld refinement, SEM measurement, absorption spectra, emission/excitation spectra, fluorescence decay analysis and emission spectra in terms of different temperature were investigated and discussed clearly. The matrix optical band gap was calculated to be 4.5  eV by reflection data, which indicated the suitable host for rare earth doping. The single doped Eu 3+ , Sm 3+ and Pr 3+ phosphors could respectively exhibit characteristic and strong red emission peaks at 614 nm, 598 nm and 642 nm when excited by (near) ultraviolet radiation. Excitingly, all samples could obtain high color purity with the value of 91.6%, 90.6% and 84.8% for Eu 3+ , Sm 3+ , Pr 3+ ions, respectively. Moreover, the thermal stability can stay strong which still keep over 75% at 150℃ when comparing with that at atmospheric temperature. The quantum efficiency (QE) is another important parameter for phosphors which were measured to be 46.6% for Eu 3+ , 53.1% for Sm 3+ and 10.3% for Pr 3+ . The present work indicates that the Sr 19 Mg 2 (PO 4 ) 14 : Re 3+ phosphors are efficient red components with extraordinary color purity and high quantum efficiency for industrial applications as solid-state lighting materials.

Effect of RE3+ electronegativities on luminescence property of Ba5Si8O21:Eu2+ persistent phosphor

Zhiliang DONG,Yi QIN,Yong YANG,Dacheng ZHOU,Xuhui XU,Jianbei QIU

A series of Ba 5 Si 8 O 21 :0.02Eu 2+ ,0.09RE 3+ persistent phosphors were synthesized by the solid-state reaction method. The measurement results of photoluminescence (PL), phosphorescence and thermoluminescence (TL) were analysed and discussed. The XRD results showed that samples codoped with different RE 3+ were Ba 5 Si 8 O 21 single pure phase. Under the excitation, all samples exhibited a broad Eu 2+ characteristic emission, and the La 3+ co-doped sample emitted the brightest photoluminescence even though its persistent luminescence property was the worst because of the weakest electronegativity. However, Nd 3+ electronegativity was suitable, thus after activation, the Ba 5 Si 8 O 21 :Eu 2+ ,Nd 3+ sample had the best persistent luminescence performance with the highest phosphorescence intensity and the persistent luminescence decay time beyond 8 h. The Nd 3+ co-doped sample also had the largest thermoluminescence integral area which proved effectively it had longer persistent luminescence time. The luminescence mechanism was also proposed to study the photoluminescence and persistent luminescence process. These results showed that RE 3+ electronegativities were distinctly important for persistent phosphors and choosing suitable electronegativity codopant was conducive to enhancing the phosphorescent performance.

Adsorption of RE3+ from aqueous solutions by bayberry tannin immobilized on chitosan

Xianying Qiu,Yueyue Shen,Ruilin Yang,Hongcheng Zhang,Shilin Zhao

Structure and Photoluminescence Properties of NaYMgWO6:RE3+ (RE = Sm, Eu) Phosphors for Solid-State Lighting

Chaofan Wang,Gen Li,Ziran Li,Dixi Ke,Haocheng Li,Junwen Huang,Ziang Wan,Mengyao Zhu,Han Zhang,Jiejun Ren,Min Zeng,Yuebin Li

Phosphor-converted light-emitting diodes (pc-LEDs) represent a key technology in solid-state lighting. However, their performance and reliability are often limited by the thermal instability of conventional phosphors under high-power operation. To address this challenge, this study reports two thermally stable red-emitting phosphors, NaYMgWO6:Sm3+ and NaYMgWO6:Eu3+, synthesized via a high-temperature solid-state reaction method. A remarkable abnormal thermal quenching behavior is observed in NaY0.97MgWO6:0.03Sm3+, whose luminescence intensity at 348 K exceeds the room-temperature value. Meanwhile, NaY0.7MgWO6:0.3Eu3+ exhibits outstanding thermal stability, retaining 80.82% of its room-temperature emission intensity at 423 K. Under near-UV and blue excitation, NaYMgWO6:Sm3+ and NaYMgWO6:Eu3+ emit intense orange-red (645 nm) and red (615 nm) light with high color purity values of 85.81% and 96.58%, respectively, and show negligible chromaticity drift up to 448 K. Notably, the internal quantum efficiency reaches 27.59% for the Sm3+-doped phosphor and 88.86% for the Eu3+-doped counterpart. Practical application is demonstrated through fabricated pc-LED prototypes, which produce bright orange-red and red emissions. Furthermore, when incorporated into white LED devices along with a commercial yellow phosphor and a blue chip, the developed red phosphors effectively compensate for the spectral deficiency in the red region, significantly improving the color rendering performance and yielding warm white light with a high color quality. These results highlight the promising potential of the developed NaYMgWO6:Sm3+/Eu3+ phosphors for high-stability solid-state lighting applications.

Crystal structure and magnetic-dipole emissions of Sr2CaWO6: RE3+ (RE=Dy, Sm and Eu) phosphors

Xiaoyu Song,Xianxian Wang,Xuewen Xu,Xin Liu,Xiaoli Ge,Fanbin Meng

The Sr 2 CaWO 6 : RE 3+ (RE = Dy, Sm and Eu) phosphors with the unusual emissions corresponding to the magnetic-dipole (MD) transition were synthesized via a sol-gel process. The crystal structure, electronic properties, photoluminescence excitation and emission spectra, and fluorescence lifetimes of the as-prepared samples were investigated. X-ray diffraction analysis confirmed that Sr 2 CaWO 6 crystallized in the monoclinic structure with the centrosymmetric monoclinic space group (P2 1 /n). The indirect band gap for Sr 2 CaWO 6 was 4.24 eV, which was calculated within the framework of density functional theory (DFT). The phosphors could be excited by the ultra-violet (UV) light at 280 nm, and exhibited characteristic emissions corresponding to the MD transitions for different RE 3+ ions. The WO 6 groups in the host lattice can absorb UV light efficiently, and then transferred the energy to activator ions. The results indicated that the doped rare earth ions occupied the centrosymmetric site in Sr 2 CaWO 6 lattice. With increasing the concentration of the dopants , the local symmetry of the activator ions can be effectively changed, which resulted in the enhancement of the characteristic emissions dominated by the electric-dipole (ED) transitions of the doped RE 3+ . The Sr 2 CaWO 6 : Sm 3+ phosphor exhibited near white emission under radiation of 280 nm.

Synthesis and Luminescence Properties of LnM v O4(M = Nb, Ta):RE3+ (RE = Eu, Tb) Nanophosphors

Huo Jiansheng,Wang Qianming

A group of LnM v O4 (M = Nb, Ta):RE3+ (RE = Eu3+, Tb3+) phosphors have been synthesized by pretreatments with a special reactor (supersonic microwave co-assistance (SMC) machine). Powder characteristics were studied by X-ray Diffraction, photoluminescence, fluorescence microscope and scanning electronic microscope. Results showed the samples can exhibit green or red emissions upon the ultra-violet excitations. The influence of SMC method on the physical properties has been investigated in detail.