Y3Al5O12:Ce3+ (YAG:Ce3+) transparent ceramic phosphors (TCPs) are regarded as the most promising luminescent converter for laser‐driven (LD) lighting. High‐quality YAG:Ce3+ TCPs are still urgent for ...high efficiency LD lighting devices. YAG:Ce3+ TCPs in a vacuum ambience by using nano‐sized raw materials are prepared. Controlling defects by adding nano‐sized MgO and SiO2 simultaneously enables a high transmittance nearly 80%. After annealing in air furthermore, the luminous efficiency is enhanced greatly from 106 to 223 lm W−1, which is the best result reported now for LD lighting. These results demonstrate that the optimizing YAG:Ce3+ TCPs in a fitting strategy will brighten once again in the next‐generation LD lighting. Based on scanning electron microscopy (SEM) coupled with a cathodoluminescence system, defects and Ce3+ distributions in grains are identified directly for the first time.
Controlling defects by adding nano‐sized MgO and SiO2 enables a high transmittance of nearly 80%. After annealing in air, furthermore, the luminous efficiency is enhanced greatly from 106 to 223 lm W−1. These results demonstrate that the optimization of Y3Al5O12:Ce3+ transparent ceramic phosphors in a fitting strategy will brighten once again the next generation of laser‐driven lighting.
Cloud top pressure (CTP) is one of the critical cloud properties that significantly affects the radiative effect of clouds. Multi-angle polarized sensors can employ polarized bands (490 nm) or O
2
...A-bands (763 and 765 nm) to retrieve the CTP. However, the CTP retrieved by the two methods shows inconsistent results in certain cases, and large uncertainties in low and thin cloud retrievals, which may lead to challenges in subsequent applications. This study proposes a synergistic algorithm that considers both O
2
A-bands and polarized bands using a random forest (RF) model. LiDAR CTP data are used as the true values and the polarized and non-polarized measurements are concatenated to train the RF model to determine CTP. Additionally, through analysis, we proposed that the polarized signal becomes saturated as the cloud optical thickness (COT) increases, necessitating a particular treatment for cases where COT < 10 to improve the algorithm’s stability. The synergistic method was then applied to the directional polarized camera (DPC) and Polarized and Directionality of the Earth’s Reflectance (POLDER) measurements for evaluation, and the resulting retrieval accuracy of the POLDER-based measurements (RMSE
POLDER
= 205.176 hPa, RMSE
DPC
= 171.141 hPa,
R
2
POLDER
= 0.636,
R
2
DPC
= 0.663, respectively) were higher than that of the MODIS and POLDER Rayleigh pressure measurements. The synergistic algorithm also showed good performance with the application of DPC data. This algorithm is expected to provide data support for atmosphere-related fields as an atmospheric remote sensing algorithm within the Cloud Application for Remote Sensing, Atmospheric Radiation, and Updating Energy (CARE) platform.
LEDs for plant lighting have attracted wide attention and phosphors with good stability and deep-red emission are urgently needed. Novel Cr3+ and Dy3+ co-doped Gd3Al4GaO12 garnet (GAGG) phosphors ...were successfully prepared through a conventional solid-state reaction. Using blue LEDs, a broadband deep-red emission at 650–850 nm was obtained due to the Cr3+ 4T2 → 4A2 transition. When the Cr3+ concentration was fixed to 0.1 mol, the crystal structure did not change with an increase in the Dy3+ doping concentration. The luminous intensity of the optimized GAGG:0.1Cr3+, 0.01Dy3+ was 1.4 times that of the single-doped GAGG:0.1Cr3+. Due to the energy transfer from Dy3+ to Cr3+, the internal quantum efficiency reached 86.7%. The energy transfer from Dy3+ to Cr3+ can be demonstrated through luminescence spectra and fluorescence decay. The excellent properties of the synthesized phosphor indicate promising applications in the agricultural industry.
CaNb2O6:Tb3+ green phosphors have been successfully fabricated via the traditional solid-state synthesis, where the nanocrystalline TbB6 is used as efficient activator. The doping effects of ...nanocrystalline TbB6 on the phase composition, the microstructure and photoluminescence of as-prepared phosphors were characterized by means of Rietveld refinement XRD, FESEM and photoluminescence measurements. As a result, all the synthesized CaNb2O6:Tb3+ phosphors are composed by the single phase of CaNb2O6. The photoluminescence (PL) spectroscopy shows that the maximum emission intensity occurred when the nanocrystalline TbB6 doping concentration is x = 0.06. Moreover, this phosphor keep the emission intensity remains about 43.3% of 300 K when its emission temperature increase to 423 K. Additionally, the white LED is fabricated by mixing present green phosphor with commercial blue and yellow phosphors, showing a white LED with the color temperature of 5152 K. On the basis of above mentioned, Ca0·94Nb2O6:0.06TbB6 phosphor can be applied as a potential green phosphor for high-performance white LED.
•Nanocrystalline TbB6 as a new type of activator can enhance the photoluminescence of CaNb2O6:Tb3+ phosphor.•Boron induces defect energy levels and prolongs the luminescence lifetime of CaNb2O6:Tb3+ phosphor.•Ca0.94Nb2O6:0.06TbB6 phosphor has excellent luminescence properties and is expected to be used in white LED.
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•The defects and crystal field environments are controlled by adding nano-sized MgO and SiO2 and annealing in air.•Al2O3 is introduced as one kind of light scatters to improve the ...blue light absorption.•The transmittance of the YAG:Ce3+ TCP is tuned from 13 % to 70 % which benefits from the flux effect of MgO and SiO2.•Prototype white LD devices in both the transmissive and the reflective model are demonstrated.
Y3Al5O12:Ce3+ (YAG:Ce3+) transparent ceramic phosphor (TCP) is one of the most promising converters for the laser-diode (LD) lighting because it has good capacity for absorbing blue light and prominent luminous efficiency (LE). A challenge is how to achieve a high-quality YAG:Ce3+ TCP to realize a high LE value. We propose a strategy to depress the defects by using the charge-balanced Mg2+-Si4+ to substitute the Al3+-Al3+. Benefiting from the flux effect of MgO and SiO2, the transmittance of the YAG:Ce3+ TCP (thickness of 1 mm) increases from 13 % to 70 % by controlling the pores in the TCP. By introducing Al2O3 to be one kind of light scatters to enhance the blue light absorption, the LE reaches 185.7 lm/W, which is much higher than the value (137 lm/W) of the same TCP previously reported. These results evidence that the optimized YAG:Ce3+ TCP has an excellent performance in LD lighting. Prototype white LD devices are demonstrated in both the transmissive and the reflective models.
Gd3Al3Ga2O12:1.5%Ce, xMg2+ (GAGG:1.5%Ce, xMg2+) transparent ceramic phosphors (TCPs) were prepared via a two-step sintering method. The effects of MgO on microstructures and luminescent properties of ...GAGG:Ce TCPs are investigated for the first time. For the optimized Mg2+ of x = 0.5%, the in-line transmittance of the obtained TCP reaches 78.6%. Performances of the titled TCPs in high-power light-emitting diodes (LEDs) and laser diodes (LDs) lighting are illustrated. The optimized TCP shows the luminous efficacy of 84.0 lm W−1 in LD lighting. This work provides a strategy to modify TCPs for the next-generation LD lighting.
A novel alkaline earth niobates red phosphor CaNb2O6:Eu3+ have been prepared through solid-state reaction, using the nanocrystalline EuB6 as a novel activator. The Rietveld refinement of XRD results ...reveal that the Eu3+ ions substitute the lattice site of Ca2+ ions and the B2− ions replace the lattice site of O2− ions, which induces the defect energy levels at the band gap of 5Dn levels and leads to higher luminescence intensity of five times higher than using the Eu2O3 activator. The CIE chromaticity coordinates of Ca0·88Nb2O6:0.12EuB6 phosphor were calculated to be (0.643, 0.34) and it is quite similar to that of pure red light. Moreover, this phosphor exhibits an excellent luminescence thermal stability. When the ambient temperature rises to 398 K (125 °C) and 423 K (150 °C), the integrated emission intensity remains 90% and 86% of their initial PL intensity at 300 K, respectively. Based on above mentioned, the Ca1-xNb2O6:xEuB6 as a NUV-excited red phosphor have a potential application for the high-performance white LEDs.
•The nanocrystalline EuB6 as a novel activator enhanced in photoluminescent of CaNb2O6:Eu3+ Phosphor.•The emission intensity of Ca0·88Nb2O6:0.12EuB6 phosphor is about five times higher than using the Eu2O3 activator.•The Ca0·88Nb2O6:0.12EuB6 phosphor exhibits an excellent luminescence thermal stability.
Y
Al
O
:Ce
(YAG:Ce
) transparent ceramic phosphors (TCPs) are regarded as the most promising luminescent converter for laser-driven (LD) lighting. High-quality YAG:Ce
TCPs are still urgent for high ...efficiency LD lighting devices. YAG:Ce
TCPs in a vacuum ambience by using nano-sized raw materials are prepared. Controlling defects by adding nano-sized MgO and SiO
simultaneously enables a high transmittance nearly 80%. After annealing in air furthermore, the luminous efficiency is enhanced greatly from 106 to 223 lm W
, which is the best result reported now for LD lighting. These results demonstrate that the optimizing YAG:Ce
TCPs in a fitting strategy will brighten once again in the next-generation LD lighting. Based on scanning electron microscopy (SEM) coupled with a cathodoluminescence system, defects and Ce
distributions in grains are identified directly for the first time.
