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On the Blue Emitting Phosphor Na <sub/>3</sub> RbMg <sub/>7</sub> (PO <sub/>4</sub> ) <sub/>6</sub> :Eu <sup>2+</sup> Showing Ultra High Thermal Stability
摘要： This work concerns a novel blue emitting LED phosphor activated by Eu2+. It turned out that this luminescent material can be efficiently pumped by near UV or UV-A radiation sources while it exhibits a high quantum yield for a doping level between 0.3 and 3.0%. More impressively, the material has a very high quenching temperature T1/2 and will thus be applicable on-chip in high power phosphor converted LEDs or even in laser diodes. The emission and thermal stability is almost identical to that of BAM:Eu2+ while the absorption band is broader and reaches into the near UV range. Therefore, Na3RbMg7(PO4)6:Eu2+ is a promising candidate as a blue emitter in high CRI full conversion LEDs. To investigate the site preference of Eu2+, DFT and Ligand Field Theory based calculations were performed to successfully predict the emission spectrum. An unusual decay behavior was observed at low temperatures and the underlying mechanism involving spin-forbidden transitions of Eu2+ is discussed.
关键词： high thermal stability,solid state lighting,Eu2+ luminescence,near UV LED,high CRI,decay time,Blue photoluminescence
更新于2025-11-21 11:18:25
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Highly efficient rare-earth-free deep red emitting phosphor La <sub/>2</sub> Li <sub/>1?y</sub> Sb <sub/>1?x</sub> O <sub/>6</sub> : <i>x</i> Mn <sup>4+</sup> , <i>y</i> Mg <sup>2+</sup> : application in high-power warm w-LEDs
摘要： Phosphor-in-glass (PiG), which serves as both a luminescent convertor and organic encapsulation material in high-power white light-emitting diodes (w-LEDs), has become a prospective research hotspot owing to its high transparency and thermal stability. However, YAG:Ce3+ PiG-based LED devices still suffer from a lack of a red component. Therefore, the development of red phosphors with excellent quantum efficiency and superior thermal stability is urgent. Herein, a highly efficient La2Li1?ySb1?xO6:xMn4+,yMg2+ red phosphor with a broadband emission ranging from 670 to 720 nm was fabricated via a conventional solid-state reaction. By co-doping Mg2+ in La2LiSbO6:Mn4+, the emission intensity was enhanced significantly, which reaches as high as 10 times that of the single-doped La2LiSbO6:Mn4+. It is proposed that the Mg2+ dopant can compensate imbalanced charges for the substitution of Sb5+ by Mn4+ and interrupt adverse energy transfer among the Mn4+ activators. Impressively, a maximum quantum yield of up to 80.3% is achieved and about 80% emission intensity is retained at the temperature of 423 K. Furthermore, the crystal field strength (Dq) and Racah parameters (B and C) together with the nephelauxetic ratio (b1) were calculated based on the obtained spectroscopic data. By embedding the red-emitting La2LiSbO6:Mn4+,Mg2+ phosphor and yellow-emitting YAG:Ce3+ phosphor into TeO2-based glass, an inorganic PiG composite as a color converter to replace organic silicone was acquired. The excellent optical parameters and tunable chromaticity feature of the fabricated w-LEDs were achieved by adjusting the mass ratio of La2LiSbO6:Mn4+,Mg2+ to YAG:Ce3+ in the PiG plate, where the correlated color temperature changed from cool white (6555 K) to warm (4130 K) and the color rendering index increased from 73.7 to 86.6 under an operating current of 300 mA.
关键词： Phosphor-in-glass,quantum yield,red phosphor,Mg2+,thermal stability,w-LEDs,Mn4+
更新于2025-11-20 15:33:11
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Aggregation-induced emission (AIE)-active highly emissive novel carbazole-based dyes with various solid-state fluorescence and reversible mechanofluorochromism characteristics
摘要： Three new carbazole-based fluorescent molecules 1-3 functionalized with tetraphenylethene have been successfully synthesized, and these compounds have high thermal stability, and they exhibited different fluorescence in solid states with the superior luminescence quantum yields of 99.04% (1), 98.90% (2) and 39.83% (3). Their aggregation-induced behaviors were explored by the study of photoluminescence spectroscopy. The results showed that luminogens 1-3 exhibited remarkable aggregation-induced emission effect. Furthermore, their distinct mechanical stimulus-responsive fluorescence characteristics were also surveyed by solid-state photoluminescence spectroscopy. Interestingly, the various emitting colors of these luminogens could be changed into the same green, and the repeatabilities of their mechanochromic luminescence behaviors were outstanding, and the powder X-ray diffraction results indicated that the reversible conversion from a crystalline to an amorphous state was responsible for the obvious mechanofluorochromism phenomena of compounds 1-3. This work will be valuable for the exploitation of mechanical-force sensors with typical aggregation-induced emission feature.
关键词： Carbazole,Mechanofluorochromism,Tetraphenylethene,Aggregation-induced emission,Different fluorescence,High thermal stability
更新于2025-11-14 15:23:50
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A novel orange–red emitting phosphor Sr2LuTaO6:Sm3+ for WLEDs
摘要： A novel double perovskite tantalite orange–red light emitting Sr2LuTaO6:Sm3+ phosphor was synthesized by the solid state reaction. The phase, crystal structure, photoluminescence properties, thermal stability and decay curves were studied. The X-ray diffraction patterns indicated that the phosphor has a pure phase of cubic phase structure. Excited by near-ultraviolet light at 407 nm, the sample exhibited three sharp emission peaks at 564 nm, 600 nm, 645 nm corresponding to the 4G5/2 → 6HJ (J = 5/2, 7/2 and 9/2) transitions, respectively. The optimum doping concentration of Sm3+ ions was determined to be 5 mol% and the concentration quenching process comes from the energy transfer among nearest-neighbor ions. The as-prepared phosphors showed excellent thermal stability, the integral intensity at 423 K is about 91.10% of the initial intensity. The CIE chromaticity coordinates of Sr2LuTaO6:Sm3+ phosphors located in orange–red region. The results suggest that Sr2LuTaO6:Sm3+ phosphors have great potential application in white light-emitting diodes.
关键词： luminescence,thermal stability,white light-emitting diodes,Sr2LuTaO6:Sm3+,phosphor
更新于2025-11-14 15:13:28
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Enhanced absorption of Sr3Lu2(BO3)4:Ce3+,Tb3+ phosphor with energy transfer for UV-pumped white LEDs
摘要： A series green emission phosphors Sr3Lu2(BO3)4:Ce3+,Tb3+ (denoted as SLBO:Ce3+,Tb3+) with broad absorption band matching well with UV LED chip were synthesized by the solid–state reaction method. The phase and structure were analyzed with XRD, EDX, FT-IR measurements. The energy transfer between Ce3+ and Tb3+ in SLBO was proved by spectra and decay curves detailedly. The emission colors vary from blue to green by adjusting the ratio of Ce3+/Tb3+ doped concentration. With temperature increasing, SLBO:Ce3+,Tb3+ phosphor shows well thermal stability that emission intensity retains 70% of its initial at 25 oC even temperature rising to 150 oC. The internal and external quantum efficiency of SLBO:3%Ce3+,8%Tb3+ are 77.5% and 34.8% under 340 nm excitation, respectively. Combining the as-synthesized SLBO:Ce3+,Tb3+ and red emission phosphor CaAlSiN3:Eu2+ coated on a 365 nm UV chip, a warm white LEDs device with CRI of 83 was achieved. All the results indicate that the SLBO:Ce3+,Tb3+ phosphor has potential application in UV pumped white LEDs.
关键词： phosphor,thermal stability,energy transfer,UV LED
更新于2025-10-22 19:38:57
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Narrow-Band Green-Emitting Sr <sub/>2</sub> MgAl <sub/>22</sub> O <sub/>36</sub> :Mn <sup>2+</sup> Phosphors with Superior Thermal Stability and Wide Color Gamut for Backlighting Display Applications
摘要： The narrow-band emitting phosphors have been extensively investigated in recent years, with the expectation that a wide color gamut of phosphor-converted backlighting device could be fabricated. Due to the weak electric–phonon interaction and low structural relaxation caused by the high rigid crystal structure and symmetric coordination environment, Sr2MgAl22O36:Mn2+ (SMAO:Mn2+) shows a narrow full-width at half-maximum of 26 nm, a high color purity of 81.5%, and a low thermal quenching (82% at 473 K of the initial intensity at 298 K). Using K2SiF6:Mn4+ as the red phosphor, SMAO:Mn2+ as the green one, and GaN-based chip as the blue component, the white light-emitting diode exhibits a National Television Standard Committee value of 127%. All the results demonstrate that the SMAO:Mn2+ phosphor has a promising application in the field of advanced wide-color-gamut backlight display, and the establishment of the relationships between the narrow-band emission and crystal structure can also be applied to design other novel narrow-band phosphors for backlighting technologies.
关键词： color gamut,inorganic phosphors,narrow-band emission,white light-emitting diodes,Sr2MgAl22O36:Mn2+,thermal stability,backlight displays
更新于2025-09-23 15:23:52
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Temperature-Dependent Electrical Characteristics of β-Ga <sub/>2</sub> O <sub/>3</sub> Diodes with W Schottky Contacts up to 500°C
摘要： The development of thermally stable contacts capable of high temperature operation are necessary for Ga2O3 high power rectifiers. We have measured the electrical characteristics of sputter-deposited W Schottky contacts with Au overlayers for reducing sheet resistance on n-type Ga2O3 before and after device operation up to 500°C. Assuming thermionic emission is dominant, the extracted barrier height decreases with measurement temperature from 0.97 eV (25°C) to 0.39 eV (500°C) while showing little change from its initial value of 0.97 eV after cooling down from each respective operation temperature. The room temperature value is comparable to that obtained by determining the energy difference between binding energy of the Ga 3d core level and the valence band of the Ga2O3 when W is present, 0.80 ± 0.2 eV in this case. The Richardson constant was 54.05 A.cm?2.K?2 for W and the effective Schottky barrier height at zero bias (eφb0) was 0.92 eV from temperature-dependent current-voltage characteristics. The temperature coefficient for reverse breakdown voltage was 0.16 V/K for W/Au and 0.12 V/K for Ni/Au. The W-based contacts are more thermally stable than conventional Ni-based Schottkies on Ga2O3 but do show evidence of Ga migration through the contact after 500°C device operation.
关键词： electrical characteristics,thermal stability,high temperature operation,Ga2O3,Schottky contacts
更新于2025-09-23 15:23:52
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Excellent thermal-stability and low dielectric loss of BaTiO3-Bi(Sr2/3Nb1/3)O3 solid solution ceramics in a broad temperature range applied in X8R
摘要： (1?x)BaTiO3-xBi(Sr2/3Nb1/3)O3 [(1?x)BT-xBSN, 0.02 ≤ x ≤ 0.1] ceramics were synthesized by a traditional solid state reaction technique. The transition from tetragonal phase to pseudo cubic phase at 0.02 ≤ x ≤ 0.04 was observed in Raman spectra and X-ray di?raction patterns. As the BSN contents increased, the grain size increased. With adding Bi(Sr2/3Nb1/3)O3, the thermal stability of permittivity and dielectric loss of ceramics got a good optimization. Especially, 0.9BT-0.1BSN ceramics have small Δε/ε25°C values (≤ ± 15%) in a wide temperature range of ?75 °C to 153 °C, high relative permittivity (～1505 to 1700) and low dielectric loss (tan δ ≤ 0.02) from ?88 °C to 200 °C, showing that BT-BSN ceramics are suitable for using in MLCCs of X8R. Impedance spectroscopy was analyzed the conduction and relaxation processes. The results showed that the relaxation and the conduction process in the high temperature region are thermally activated, and the oxygen vacancies are charge carriers.
关键词： Thermal stability,Dielectric properties,Impedance,Phase evolution
更新于2025-09-23 15:23:52
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Thermally-stable large strain in Bi(Mn0.5Ti0.5)O3 modified 0.8Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3 ceramics
摘要： A N U S C RIP T (1-x)[0.8Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3]-xBi(Mn0.5Ti0.5)O3 (x = 0 ~ 0.06, BNKMT100x) lead-free ferroelectric ceramics were prepared via solid state reaction method. Bi(Mn0.5Ti0.5)O3 induces a structure transition from rhombohedral-tetragonal morphotropic phases to pseudo-cubic phase. Moreover, the wide range of compositions within x = 0.03 ~ 0.055 exhibit large strain of 0.31% ~ 0.41% and electrostrictive coefficient of 0.027 ~ 0.041 m4/C2. Especially, at x = 0.04, the large strain and electrostrictive coefficient are nearly temperature-independent in the range of 25 ~ 100 °C. The impedance analysis shows the large strain and electrostrictive coefficient originate from polar nanoregions response due to the addition of Bi(Mn0.5Ti0.5)O3.
关键词： large strain,thermal stability,composition-insensitivity,lead-free,electric property
更新于2025-09-23 15:23:52
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Crystallization kinetics and thermal stability of ZrO <sub/>2</sub> monolithic aerogel improved by SiO <sub/>2</sub> layer
摘要： ZrO2 aerogel modified by SiO2 (ZSA) was synthesized by aging ZrO2 gel in tetraethoxysilane (TEOS) solution using ZrOCl2·8H2O as precursor, and 1,2-propylene oxide (PO) as gelation agent followed by ethanol supercritical fluid drying. Crystallization kinetics and thermal stability of ZSA while calcined at elevated temperature were studied comparing with pure ZrO2 aerogel. The prepared samples were characterized using TG-DSC, N2 adsorption/desorption, SEM and TEM. The results show that thermal stability of ZSA are highly improved due to the SiO2 layer hindering the proliferation, nucleation and growth process of ZrO2.
关键词： ZrO2,thermal stability,aerogel,SiO2,crystallization kinetics
更新于2025-09-23 15:23:52