Luminescence enhancement of Cr3+ doped garnet phosphor for high-performance LED towards smart NIR light source

Cr³⁺ doped phosphor shows great potential for near-infrared (NIR) light-emitting diodes (LED), but it suffers from low quantum efficiency and poor thermal stability. Herein, a novel Cr³⁺ doped broadband NIR garnet Ca₃Sc₂Ge₃O₁₂ phosphor was developed. The multisite structure of the emission band is investigated by site-selective spectroscopy and is attributed to the octahedral Cr³⁺ perturbed by defects. Moreover, we propose different strategies to enhance the luminescence of the phosphor, including enhancement of crystallinity and elimination of defects. Compared with the initial sample, the emission intensity of the optimized phosphor is improved for 8.6 times. The optimal Ca₃Sc₂Ge₃O₁₂: 0.06Cr³⁺ phosphor exhibits excellent thermal stability. At 423 K, the integral emission intensity of the optimal sample remains 94.7% of that at room temperature. Finally, high-performance NIR LED was fabricated using a blue LED and the title phosphor. The packaged LED lamp has high radiance (109.3 mW@300 mA) and photoelectric efficiency (15.96%@40 mA). Our study not only provides a boulevard for enhancing the luminescence of Cr doped NIR phosphor, but also gives a new perspective for understanding the multisite luminescence of Cr³⁺ in garnet host.     

Stable and efficient all-inorganic color converter based on phosphor in tellurite glass for next-generation laser-excited white lighting

Laser lighting is considered as a next-generation high-power lighting due to its high-brightness, directional emission, and quasi-point source. However, thermally stable color converter is an essential requirement for white laser diodes (LDs). Herein, we proposed a stable and efficient phosphor-in-glass (PiG) in which YAG:Ce³⁺ and MFG:Mn⁴⁺ phosphors were embedded into tellurite glass matrixes. The glass matrixes with low-melting temperature and high refractive index were prepared by designing their composition. The luminescence of YAG:Ce³⁺ PiGs was adjusted by controlling phosphor thickness. Aiming to compensate for red emission, multi-color PiGs were realized by stacking MFG:Mn⁴⁺ layers on YAG:Ce³⁺ layer. The phosphor crystals are chemically stable and maintain intact in the glass matrix. Furthermore, white LDs were fabricated by combining the PiGs with blue LDs. As the phosphor thickness increases, the chromaticity of white LDs shifts from cool to warm white, and the white LDs exhibit excellent thermal stability under different excitation powers.     

Efficient near-infrared pyroxene phosphor LiInGe2O6:Cr3+ for NIR spectroscopy application

Broadband near-infrared phosphors are essential to realize nondestructive analysis in food industry and biomedical areas. Efficient long-wavelength (>830 nm) phosphors are strongly desired for practical applications. Herein, we demonstrate an efficient broadband NIR phosphor LiInGe₂O₆:Cr³⁺, which exhibits a broad NIR emission peaking at ~880 nm with a full width at half maximum of 172 nm upon 460 nm excitation. The internal/external quantum efficiencies of LiInGe₂O₆:Cr³⁺ are measured to be 81.2% and 39.8%, respectively. The absorption of the phosphor matches well with commercial blue LEDs. Using the fabricated phosphor converted LED illuminating human palm, distribution of blood vessels can be clearly recognized under a NIR camera. These results indicate that LiInGe₂O₆:Cr³⁺ is a promising candidate to be used in future non-destructive biological applications.     

A novel pale-yellow Ba2ZnGe2O7:Bi3+ phosphor with site-selected excitation and small thermal quenching

A novel pale-yellow Ba₂ZnGe₂O₇:Bi³⁺ phosphor with site-selected excitation and small thermal quenching was synthesized by conventional solid-state sintering. The crystal structure and luminescence properties have been investigated in detail for the first time using XRD patterns, photoluminescence spectra, diffuse reflection spectra, decay curves, and temperature-dependent emission spectra. The results reveal that the excitation spectrum of Ba₂ZnGe₂O₇:Bi³⁺ phosphor locates in the near-ultraviolet region of 300-400 nm, and its emission shows an obvious site-selective excitation phenomenon since Bi³⁺ ions occupy two different crystallographic sites in the Ba₂ZnGe₂O₇ host. When excited under 360 nm, the phosphors show a pale-yellow emission in the range of 400-700 nm with the maximum peaking at 520 nm, while when excited under 316 nm, the phosphors show a blue emission in the range of 400-700 nm with the maximum peaking at 480 nm. In addition, the emission of Ba₂ZnGe₂O₇:Bi³⁺ can also be easily controlled by changing the Bi³⁺ concentration. The Ba₂ZnGe₂O₇:Bi³⁺ phosphor has small thermal quenching, and its emission intensity only decreases by 2% at 200°C. The results indicate that this novel pale-yellow Ba₂ZnGe₂O₇:Bi³⁺ phosphor could be conducive to the development of white light-emitting diodes.     

Dy3+-doped Y2Zr2O7 highly transparent ceramics for ultraviolet excitable warm white light-emitting applications

Attaining effective warm white light emitting in functionally advantageous transparent polycrystalline ceramics is vitally important to guarantee the development of both human and botanical systems. In response to this aim, a series of Dy³⁺-doped Y₂Zr₂O₇ (YZO) transparent ceramics were prepared via a solid-state reaction and vacuum sintering approach in this work. These fabricated ceramics show high transparency, where the in-line transmittance at 700 nm is about 76%, which is very close to the theoretical limit (78%). In addition, under the excitation of UV light sources (358 and 384 nm), strong warm white light emissions were observed in these YZO:Dy transparent ceramics. The corresponding photoluminescence characteristics and mechanisms of YZO:Dy ceramics are investigated carefully. The Dy-doped YZO ceramics integrate with high transparency and UV-excitable warm white light emission properties, making them promising light-emitting converter materials for light-emitting source applications.     

Overcoming the cyan gap for full-spectrum lighting using cation-substitution-induced rigid Ca2YZr2Al3O12:Ce3+

Mixing multicolor phosphors for simulating the full spectrum of sunlight illumination is a popular solution to obtain high-quality white light. However, there is still a need to overcome the cyan gap in the emission spectrum. In this work, a series of garnet Ca₂Y_0.94–xLu_xZr_2–yHf_yAl₃O₁₂:6%Ce³⁺ (abbreviated as CY_0.94–xLu_xZr_2–yHf_yA:Ce³⁺) cyan phosphors are designed and prepared by substituting Y³⁺ and Zr⁴⁺ in Ca₂YZr₂Al₃O₁₂:6%Ce³⁺ with Lu³⁺ and Hf⁴⁺ with smaller ionic radius and larger mass. Under 405 nm violet light excitation, the optimized Ca₂Y_0.88Lu_0.06Hf₂Al₃O₁₂:6%Ce³⁺ (CY_0.88Lu_0.06Hf₂A:Ce³⁺) shows a bright cyan emission band in the range of 430–750 nm with the peak at 477 nm. Importantly, the emission intensity and thermal stability properties of CY_0.88Lu_0.06Hf₂A:Ce³⁺ were significantly improved by 58% and 47% compared to those of pure Ca₂YZr₂Al₃O₁₂:Ce³⁺. Small and heavy cation substitution could induce highly stable rigid structure, thus enhancing emission intensity and stability. The color rendering index increases from 84.5 to 92.0 after supplementing CY_0.88Lu_0.06Hf₂A:Ce³⁺ phosphor in white light-emitting diode devices combining commercial red, green, and blue phosphors with a violet chip, indicating its practical application in full-spectrum lighting. The present study provides promising strategies for the design and development of efficient cyan materials for high-quality full visible spectrum light-emitting diode lighting.     

纳米Y_2O_3催化合成无毒增塑剂柠檬酸三丁酯

用柠檬酸和正丁醇为原料,以纳米Y2O3催化合成无毒增塑剂柠檬酸三丁酯,探讨了催化剂用量、酸醇物质的量比、反应时间、反应温度对酯化率的影响,对合成的产品进行红外光谱分析。实验结果表明,纳米Y2O3催化合成柠檬酸三丁酯的最佳条件为:n(柠檬酸)∶n(正丁醇)=1∶4.5,催化剂用量为柠檬酸质量的3.5%,反应温度114~153℃,反应时间2.5 h,酯化率可达90.06%,产品纯度>98.88%。     

A reddish orange stoichiometric phosphor LiEu(PO3)4 for white light-emitting diodes

Stoichiometric phosphors LiGd_1−xEu_x(PO₃)₄(x=0, 0.2, 0.4, 0.6, 0.8, 1.0) were synthesized via traditional solid state reactions. The X-ray powder diffraction measurements show that all prepared samples are isostructural with LiNd(PO₃)₄. Eu³⁺ doped phosphors can emit intense reddish orange light under the excitation of near ultraviolet light from 370 to 410 nm. The strongest two at 591 and 613 nm can be attributed to the transitions from excited state ⁵D₀ to ground states ⁷F₁ and ⁷F₂, respectively. The typical chromaticity coordinates (x=0.620, y=0.368) of Eu³⁺ doped phosphors are in red area. The recorded absorbance spectra indicate that there is effective absorbance in the near UV region for all Eu³⁺ doped samples. Present research indicates that LiGd_1–xEu_x(PO₃)₄ is a promising phosphor for white light-emitting diodes.     

Synthesis and photoluminescence properties of MgAl(PO4)O:Eu red phosphor for white LEDs

Eu³⁺-activated MgAl(PO₄)O:phosphor has been synthesized by a high temperature solid state reaction and efficient red emission under near-ultraviolet excitation is observed. The emission spectrum shows a dominant peak at 594 nm due to the ⁵D₀→⁷F₁ transition of Eu³⁺. The excitation spectrum is coupled well with the emission of UV LED (350–410 nm). The effect of Eu³⁺ concentration on the luminescent properties of MgAl(PO₄)O:Eu³⁺ and the mechanism of concentration quenching of Eu³⁺ are studied. The results show that MgAl(PO₄)O:Eu³⁺ is a promising red-emitting phosphor for white LEDs.     

Facile synthesis of the desired red phosphor Li2Ca2Mg2Si2N6:Eu2+ for high CRI white LEDs and plant growth LED device

The red emission with suitable peak wavelength and narrow band is acutely required for high color rendering index (CRI) white LEDs without at the cost of the luminous efficacy. Herein, the Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ red phosphor was prepared with facile solid-state method using Ca₃N₂, Mg₃N₂, Si₃N₄, Li₃N, and Eu₂O₃ as the safety raw materials under atmospheric pressure for the first time, which shows red emission peaking at 638 nm with full width at half maximum (FWHM) of 62 nm under blue light irradiation and becomes the desired red phosphor to realize the balance between luminous efficacy and high CRI in white LEDs. The morphology, structure, luminescence properties, thermal quenching behavior, and chromaticity stability of the Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ phosphor are investigated in detail. Concentration quenching occurs when the Eu²⁺ content exceeds 1.0 mol%, whereas high-temperature photoluminescent measurements show a 32% drop from the room-temperature efficiency at 423 K. In view of the excellent luminescence performances of Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ phosphor, a white LEDs with CRI of 91 as a proof-of-concept experiment was fabricated by coating the title phosphor with Y₃Al₅O₁₂:Ce³⁺ on a blue LED chip. In addition, the potential application of the title phosphor in plant growth LED device was also demonstrated. All the results indicate that Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ is a promising red-emitting phosphor for blue LED-based high CRI white LEDs and plant growth lighting sources.     

Kinetic investigation of ZrO2, Y2O3, and Ni on poly(vinyl butyral) thermal degradation using nonlinear heating functions

The effects of zirconia (ZrO₂), yttria (Y₂O₃), and nickel (Ni) on poly(vinyl butyral) (PVB) thermal degradation were evaluated using kinetic analysis of TGA data and nonlinear heating rates. An exact solution derived from the Arrhenius equation in an integration form was used for the kinetic analysis. The kinetic parameters of the thermal degradation reaction were determined utilizing the solution and the isoconversional principle. Results show that the reaction pathway of the PVB thermal degradation was altered by the presence of these inorganic materials except ZrO₂. The strong catalytic effects of Y₂O₃, and Ni on the PVB degradation were found and discussed according to the analytical results. The reaction rate was accelerated faster in lower temperatures in the presence of Y₂O₃, and Ni. The degradation period of the PVB/Ni sample appeared the shortest for these cases. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2552–2559, 2006     

Scalable and tunable Y2O3-MgO composite for infrared transparency applications

The process-structure-property correlationships in yttria-magnesia (YM) composite have been investigated. YM composite was synthesized using commercial powders via ball-milling route with three different grinding balls (Si₃N₄, Al₂O₃, ZrO₂) having two different sizes (2 and 5 mm diameter). The alteration in grinding ball material and size produces sintered ceramic having different grain sizes (420–560 nm) and degree of phase mixing homogeneity (0.40–0.70). The contamination induced by the milling ball resulted in changes in Y₂O₃ and MgO defect chemistry, which influenced the grain growth behavior in the YM composite. The hot-pressed composite prepared using 2-mm Si₃N₄ ball-milled powders exhibited the finest grain size (420 nm) and better phase mixing homogeneity (0.63). The subsequent impact was seen on transmittance efficiency (71%) over the 3–7-μm wavelength range, which is ∼85% of the theoretical limit. The findings show that the selection of the right size and type of grinding ball for milling commercial powder is a simple and cost-effective way for scalable production of YM composite with high transmittance efficiency for infrared windows and dome applications.     

Effects of calcination atmosphere on monodispersed spherical particles for highly optical transparent yttria ceramics

Highly sinterable powders are required for the fabrication of transparent ceramics. Here, we studied the effects of calcination atmosphere on the characteristics of monodispersed spherical Y₂O₃ powders, such as crystallite size and particle density, for high optical transparent ceramics. It was found that vacuum calcination around the crystallization temperature is the crucial step to eliminate intragranular pores in the spherical particle. The fast decomposition rate in a vacuum creates smaller crystallites, and the following higher calcination temperature results in the enhancement of pore elimination. The in‐line transmittance of the transparent Y₂O₃ ceramics, vacuum sintered at 1750°C, was improved by increasing the particle density of the as‐calcined powders. This result indicates that the high‐density starting particles effectively enhance the pore elimination during the fabrication of transparent Y₂O₃ ceramics.     

Improving antifouling performance for the harvesting of Scenedesmus acuminatus using Fe2O3 nanoparticles incorporated PVC nanocomposite membranes

Membrane filtration provided a potential solution to get high quality microalgae biomass and recyclable medium. However, the fouling of membrane by microalgae cells and organic matter greatly affects membrane harvesting efficiency. In this study, membrane performance was tested in terms of flux declining and backwashing recovery for microalgal harvesting. Compared with the unmodified poly(vinyl chloride) (PVC) membrane, the membrane with 1.0% Fe₂O₃ incorporation had a 66% increase in average flux, reaching 138 L m⁻ h⁻¹. Foulants on the membrane surface were characterized using attenuated total reflection-Fourier transform infrared (ATR-FTIR) and confocal laser scanning microscope (CLSM), as well as sodium hydroxide extraction followed by total organic carbon (TOC) quantification and fluorescence excitation–emission matrix (FEEM) identification of organic components. FEEM and TOC analysis of the extracted foulants revealed that the surface of 1.0% Fe₂O₃ incorporated membrane had less fouling than the unmodified PVC membrane, which may be attributed to its hydrophilicity after Fe₂O₃ incorporation. CLSM analysis and ATR-FTIR analysis of the fouled membrane surface further revealed that the protein substance on the 1.0% Fe₂O₃ incorporated PVC membrane was lower than those in the unmodified membrane, which further confirmed the enhanced antifouling performance of the 1.0% Fe₂O₃ incorporated PVC membrane. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47685.     

SDBS辅助合成Y2O3/Ag3VO4光催化剂及其催化可见光降解罗丹明B

以V2O5, AgNO3和Y(NO3)3×6H2O为原料、十二烷基苯磺酸钠为辅助剂,采用直接沉淀法和浸渍法制备单斜晶相Ag3VO4和Y2O3/Ag3VO4复合催化剂,表征了产物的结构和形貌,并分析了其形成机理;在可见光下研究了其催化可见光降解罗丹明B(RhB)的性能. 结果表明,所得Y2O3/Ag3VO4复合催化剂吸收边相对纯相Ag3VO4发生红移,禁带宽度减小至1.83 eV,电子-空穴对复合几率降低,对RhB有较好的可见光催化活性和稳定性,可见光照射15 min后,0.08 g 3% Y2O3/Ag3VO4催化200 mL 8 mg/L RhB溶液的降解率达94.2%.     

不锈钢板负载V2O5-WO3-TiO2催化剂制备及其催化还原脱硝性能

以溶胶-凝胶法制备的TiO₂粉末为载体,偏钒酸铵和水合钨酸铵溶液为浸渍液,采用分步浸渍法制备了V₂O₅-WO₃-TiO₂催化剂,以聚乙烯醇-硅溶胶为黏合剂,采用涂覆法将催化剂粘合于经硫酸和钛酸丁酯溶胶处理过的不锈钢板板材表面,获得不锈钢板负载的V₂O₅-WO₃-TiO₂催化剂。采用XRD、FT-IR和SEM等表征手段对催化剂进行表征,结果表明,V₂O₅-WO₃-TiO₂催化剂可均匀负载于不锈钢板表面。采用氨选择性催化还原氮氧化物法研究了催化剂的脱硝性能,结果表明,在空速8 000 L·（kg·h）^-1和反应温度360 ℃的条件下,NOx脱除率超过92%,且制备的催化剂具有良好的稳定性和耐硫性。     

Synthesis and luminescent characteristics of yellow emitting GdSr2AlO5:Ce phosphor for blue light based white LED

A series of Ce³⁺ ions doped GdSr₂AlO₅ (GSA) phosphors were synthesized by a citric acid based sol–gel method. The X-ray diffraction patterns confirmed their tetragonal structure after the samples were annealed at 1300 °C, and the scanning electron microscope image showed the closely packed particles. The excitation spectra revealed that the GSA phosphor effectively excited with blue light of 442 nm due to the 4f¹→5d¹ transition and exhibited yellow emission corresponding to the 5d¹→4f¹ transition of Ce³⁺ ions. The optimum doping concentration of Ce³⁺ ions was 5 mol% and the critical distance was calculated to be ~17 Å. White LEDs were fabricated by combining blue LED (465 nm) chip with Ce³⁺:GSA phosphor. The CIE chromaticity coordinates (0.34, 0.31) provide their emission potentiality in the white light region.