CRI Values Research Articles

Research on the influence of parameters on the fracture performance of the large stone asphalt mixture based on the semi-circular bending test

Pavement failure is a main type of road damage. To investigate the fracture performance of asphalt mixtures with large aggregates, this study utilized the semi-circular bending test to compare the specimens of LSAM-30 (the large stone asphalt mixture) and AC-13 (the fine aggregate asphalt mixture). The research focuses on examining the effects of specimen thickness, notch length, loading rate, and test temperature on the fracture performance. In the assessment of the experimental outcomes, this study employs fracture energy, J-integral, BCI, and CRI as parameters for comparison. The findings demonstrate that under the same conditions, the large stone asphalt mixture exhibits higher peak load, greater fracture energy, higher BCI and CRI values, as well as better J-integral fracture toughness in comparison to the fine aggregate asphalt mixture. At 20°C, the crack path in the large stone asphalt mixture (LSAM) circumvented the large aggregates and thus presented to be bent and long, while the crack in the fine aggregate asphalt mixture was shorter and straighter. The longer and more curved crack path in the LSAM consumed greater energy, resulting in better fracture resistance. At 0°C, the cracks in both asphalt mixtures were linear, but the large aggregate mixture required a stronger load to damage the larger aggregates. Therefore, the LSAM demonstrates a slightly better fracture resistance at low temperatures. In conclusion, the higher peak load, fracture energy, BCI, and CRI of the LSAM indicate a superior fracture performance. The longer and more curved crack path implies greater energy consumption during the fracture. As a result, the LSAM exhibits better fracture performance and resistance to pavement failure compared with the fine aggregate asphalt mixture.

Effects of Na+, Ga3+ introduction on the luminescence properties of LiAl4O6F: Mn4+ red fluorescent materials

LiAl4O6F (LAOF): Mn4+, Na+, Ga3+ red fluorescent materials were prepared by high temperature solid phase method. The properties of LAOF: Mn4+, Na+, Ga3+ phosphors were characterized by X-ray diffraction (XRD), photoluminescence (PL) spectra, variable temperature spectroscopy, scanning electron microscopy (SEM) and other tests. Under the excitation of 450 nm light, an intense red emission peak was observed around 662 nm, corresponding to the 2Eg→4A2g transition of Mn4+. Compared with Mn4+ single doping, the introduction of Na+, Ga3+ greatly improves the luminescence intensity of LAOF. The photoluminescence quantum yield of the optimal LAOF: 0.2%Mn4+, 0.2%Na+, 3%Ga3+ phosphor was measured to be 41.6%. The prepared sample have excellent thermal and water stability. Meanwhile, the w-LED device with a beneficial luminescence efficiency (LE = 331.7 lm W−1), exhibited good CRI and CCT values. These results indicate that LAOF: Mn4+, Na+, Ga3+ phosphors have potential application prospects as a red component in the field of lighting display.

Surface passivation of red-emitting fluoride phosphors by aminocarboxyl complexants to achieve high water-resistance for light-emitting diodes

Mn4+-activated fluoride phosphors are promising luminescent materials for use in phosphor-converted white-light-emitting diodes (wLEDs). However, poor water resistance in high humidity environment, one of critical drawbacks of this type of phosphors, has limited their practical applications. To address this issue, we developed a new facile strategy to passivate the surface of phosphors by in situ constructing a dual Mn4+-rare protective layer using well-known aminocarboxyl complexants with mild reducibility and strong complexation property. Ethylenediamine tetraacetic acid (EDTA) was taken as a representative for the research in detail, and a typical Mn4+-doped fluorosilicate phosphor K2SiF6:Mn4+ (KSFM) was selected to demonstrate the reliability of the proposed strategy. The surface passivation was achieved by simply dispersing KSFM in a saturated EDTA aqueous solution (KSFM-sEDTA) or a hydrofluoric acid solution containing a certain amount of EDTA (KSFM-EDTA), and then stirring for a short time at room temperature. The analysis results indicate that the dual Mn4+-rare surface layer is composed of a K2SiF6 matrix shell and an organic coating of residual EDTA and/or its related compounds, and the layer constructed by Method 2 is more significant than that by Method 1. Both the luminescence performance and the water resistance of the passivated KSFM were greatly enhanced while the luminescence characteristics remained unchanged. When the water-eroded KSFM was re-treated with EDTA, the luminescence was dramatically restored due to removal of the manganese hydrolysates and repair of the crystal surface defects. The wLEDs assembled with KSFM-EDTA and KSFM-sEDTA phosphor exhibited intense white light with high luminous efficiency (LE, 170.61 lm/W and 162.51 lm/W), high color rendering index (CRI, 88.3 and 85.9), and low correlated color temperature (CCT, 3680 K and 3805 K), respectively. More importantly, the fabricated wLEDs retained high LE (90.6% and 88.6%) and no remarkable changes of CRI and CCT values after being aged at high temperature and humidity (85 °C, 85%) for 550 h, which are more superior to the wLED assembled with the pristine KSFM.

Tunable emission, energy transfer and cation substitution in the Li2Sr2Al(PO4)3:Dy3+, Eu3+, Na+ phosphor for WLEDs application

The current investigation deals with the synthesis and characterization of the singly, double and triple ions (Dy3+, Eu3+, Na+) co-doped Li2Sr2Al(PO4)3 phosphors. The entire series of suggested phosphors has been successfully synthesized using a straightforward combustion method and their XRD and Rietveld refinement pattern confirms the phase formation and successful synthesis of material. The morphological behaviour, elemental composition, vibrational features, thermal stability and luminescence properties were carried out by SEM-EDAX analysis, FT-IR, TG-DTA and photoluminescence techniques. The single Dy3+ doped Li2Sr2Al(PO4)3 phosphors exhibits blue and yellow emission band around at 482 nm and 572 nm monitored at 350 nm, 365 nm, 388 nm excitation. While, Eu3+ doped Li2Sr2Al(PO4)3 phosphors exhibits orange and red emission band around at 592 nm and 615 nm under 395 nm and 466 nm excitation. According to Froster and Dexter theory, the PL excitation spectrum Dy3+ doped Li2Sr2Al(PO4)3 phosphor and Eu3+ doped Li2Sr2Al(PO4)3 phosphor are overlapped to each other. Consequently, an investigation was conducted to study the transfer of energy between Dy3+ and Eu3+. In addition, to improvement in emission intensity and color tunning host cation (Li+) replaced with another cation (Na+) and their impact was studied. The photometric characterization like CRI Chromaticity coordinate, CRI and CCT values are also estimated using color calculator. The host cation substitution revealed that performance of Dy3+/Eu3+ doped Li2Sr2Al(PO4)3 phosphors were improved with doping of Na+ ions. The overall study and their estimated results suggested that Dy3+, Eu3+, Na+ ions doped Li2Sr2Al(PO4)3 phosphors have huge ability for WLEDs application and their future investigation.

Isolation and characterization of bacterial cellulose produced from soybean whey and soybean hydrolyzate

Soybean whey and soybean hydrolyzate can be used for the biotechnological production of high-value products. Herein, we isolate soybean whey (SW)-and soybean hydrolyzate (SH)-derived bacterial cellulose (BC, produced by kombucha) and characterize it by a range of instrumental techniques to reveal differences in micromorphology, crystallinity, and themal behavior. Studies have shown that the amounts of wet state BC produced from HS, SW and SH was 181 g/L, 47 g/L and 83 g/L, respectively. The instrumental analysis of BC, included SEM, AFM, FT-IR, XRD and TGA. It is shown that the FT-IR spectra of BC have a similar character, but we found differences in the micromorphology,crystallinity and thermal temperature of BC. The minimum average widths of the fibers produced from SH medium was 100 ± 29 nm. The CrI values of BC produced from SH medium was 61.8%. The maximum thermal degradation rate temperature of BC produced from SW medium was 355.73 °C. The combined results demonstrate that soybean industrial waste can be used as a cost-effective raw material for BC production.

Development of ultra-broad band light emitting single phase garnet phosphor based on energy transfer mechanism and its applications in optical temperature sensing and WLED

Cerium (Ce3+) doped garnet phosphor has received much attention for optoelectronic device applications. However, the family of Ce3+ doped garnet phosphors suffers from deficiency of red component in their emission spectrum. Herein, authors present a strategy to improve red component through widening of emission band with the incorporation of Cr3+ co-dopant in the garnet structure. In view of this authors have prepared a series of Ce3+ doped and Ce3+/Cr3+ co-doped Gd3Al4GaO12 (GAGG) garnet using the facile solid state reaction method. The structural studies of prepared garnet is done with the help of X-ray diffraction (XRD) study. The photoluminescence study demonstrates that Ce3+/Cr3+ co-doped garnet sample emits an ultra-broad emission band ranging from 490 nm to 850 nm under suitable excitations. The ultra-broad band is observed due to the combination of emission bands originating from the transitions of Ce3+ and Cr3+. The Ce3+/Cr3+ co-doped garnet sample is also studied to examine the optical thermometric ability with the help of the luminescence intensity ratio (LIR) technique. Finally, the selected samples with optimized compositions GAGG: 6.0 %Ce3+ and GAGG:6.0 %Ce3+/1.5 %Cr3+ were used to fabricate pc-WLED device by the coating of phosphor layer over commercially available blue LED chip (InGaN). The fabricated pc-WLED device has shown good voltage stability as well as good LED performance parameters CRI (>70) and CCT (<4000K) values. Present results may stimulate the exploration of optical tuning via the incorporation of additional dopants such as Cr3+ in Ce3+ doped garnet phosphor for optical thermometry and pc-WLED.

Interrelation of gas blowing parameters of blast furnaces and the main quality indicators of coke in the conditions of JSC “Ural Steel”

The aim of the study was to establish the relationship between the gas blowing parameters of a blast furnace (BF) and the quality indicators of coke CRI, CSR and to develop recommendations on the use of measures to increase CSR and reduce CRI in order to increase BF productivity and reduce coke specific consumption. For an objective study, BF No. 1 was chosen with a useful volume of 1007 m3, which worked during the study period with consistently high technical and economic indicators. The results of the analysis of data on the effect on the gas-blast parameters (flow rate and blast pressure) of blast furnace No. 1 of the values of coke reactivity CRI and coke hot strength CSR over a three-year period are presented. Research has revealed that the CRI and CSR values of the coke used at the enterprise do not correspond to the recommended values. A relationship has been established between the gas blowing parameters of a blast furnace and the indices of coke reactivity CRI and hot strength of coke CSR. Measures are proposed to improve coke CRI (decrease) and CSR (increase) in the conditions of Ural Steel JSC, the implementation of which will increase the productivity of blast furnaces and reduce the specific consumption of coke.

Synthesis and luminescence enhancement of white-emitting Ca9La(VO4)7:Dy3+ phosphors through Gd3+ and Al3+ codoping for white-light-emitting diodes

The single-component Ca9La(VO4)7:Dy3+, Gd3+ and Ca9La(VO4)7:Dy3+, Al3+ white-emitting phosphors were prepared through a solid-state method, and the Gd3+/Al3+ was introduced in the structure for photoluminescence enhancement. The XRD results verified that the structure of samples was consistent with the Ca9La(VO4)7 standard phase. The as-prepared Ca9La(VO4)7:Dy3+ exhibited a characteristic white emission consisting of a yellow peak (570 nm) and a blue peak (478 nm), which originated from the electron transitions 4F9/2→6H13/2 and 4F9/2→6H15/2 of Dy3+, respectively. Through the introduction of Gd3+/Al3+ into Ca9La(VO4)7:Dy3+, the luminescence intensity could be enhanced by 1.520 and 1.522 times, respectively, which are due to the crystal-field environmental effect. By combining the Ca9La0.79(VO4)7:0.18Dy3+, 0.03Gd3+ and Ca9La0.82(VO4)6.97:0.18Dy3+, 0.03Al3+ with a n-UV LED chip (λex = 365 nm), the warm w-LEDs with suitable CCT and CRI values were realized. In summary, the Gd3+/Al3+ introduced Ca9La(VO4)7:Dy3+ samples can serve as excellent white-emitting phosphors for white-light-emitting diode applications.

Remarkable White Circularly Polarized Electroluminescence Based on Chiral Co‐assembled Helix Nanofiber Emitters

AbstractWhite circularly polarized organic light‐emitting diodes (CP‐WOLEDs) are of great significance in potential lighting sources and full‐color 3D displays. However, High‐performance white CP‐EL sources are almost unexplored. We have constructed full‐color CP‐EL devices based on chiral co‐assemblies by using three achiral conjugated pyrene‐based dyes (BP, w‐WP and c‐WP) doped with chiral binaphthyl‐based enantiomers (S‐/R‐M) as the EMLs through an intermolecular chirality induction mechanism. (S‐/R‐M)0.2‐(c‐WP)0.8 films exhibit regular helix nanofibers under annealing treatment and emit strong white CPL. Significantly, remarkable CP‐WOLEDs based on (S‐/R‐M)0.2‐(c‐WP)0.8 were achieved with |gEL| values as high as 6.2×10−2 and an excellent CRI of 98 at the CIE coordinates of (0.33, 0.33). These are the highest gEL and CRI values of reported CP‐WOLEDs to date. This is the first achievement of CP‐WOLEDs based on chiral co‐assembled helix nanofiber emitters, and provides a valuable strategy with which to develop white CP‐EL for future practical applications.

Remarkable White Circularly Polarized Electroluminescence Based on Chiral Co-assembled Helix Nanofiber Emitters.

White circularly polarized organic light-emitting diodes (CP-WOLEDs) are of great significance in potential lighting sources and full-color 3D displays. However, High-performance white CP-EL sources are almost unexplored. We have constructed full-color CP-EL devices based on chiral co-assemblies by using three achiral conjugated pyrene-based dyes (BP, w-WP and c-WP) doped with chiral binaphthyl-based enantiomers (S-/R-M) as the EMLs through an intermolecular chirality induction mechanism. (S-/R-M)0.2 -(c-WP)0.8 films exhibit regular helix nanofibers under annealing treatment and emit strong white CPL. Significantly, remarkable CP-WOLEDs based on (S-/R-M)0.2 -(c-WP)0.8 were achieved with |gEL | values as high as 6.2×10-2 and an excellent CRI of 98 at the CIE coordinates of (0.33, 0.33). These are the highest gEL and CRI values of reported CP-WOLEDs to date. This is the first achievement of CP-WOLEDs based on chiral co-assembled helix nanofiber emitters, and provides a valuable strategy with which to develop white CP-EL for future practical applications.

Fabrication of W-LEDs by Coating Tri-Color Inorganic Phosphors on UV-Diode

YAG:Ce phosphor coated on blue-chip gives many advantages, except the color rendering of the LEDs fabricated by this method is poor due to the lack of red and green colors. This problem can be sorted out by choosing different methods out of the available two different methods. For the first method, the n-UV (near-ultraviolet) LED is coated with a mixture of intense blue, green, and red phosphors to make a white light-emitting diode. Also, if the yellow color phosphor is added, lamps can give better CRI values. So many papers are reported on this type of white LED fabrication technique. In this paper, we have reported the fabrication of white LED lamps by coating three different phosphors i.e. blue, green, and red in the appropriate amount to be mixed and coated on the near UV LED chips. This approach is different from the existing reports because we are using near UV (405-407 nm LEDs) not the UV LED chips in the fabrication of white LEDs in this paper.

Bioaccumulation of Heavy Metals in a Soil–Plant System from an Open Dumpsite and the Associated Health Risks through Multiple Routes

Screening various plant species to act as hyperaccumulators and associated health risks could serve as a sustainable solution for the bioremediation heavy metals (HMs). For the first time, the present study explored the phytoremediation potential of native plants, soil enrichment, and human health risks associated with the contamination of HMs in soil and plant samples collected from a municipal solid-waste open dump site. Soil and plant samples (n = 18 + 18) from the dumpsite and (n = 18) from the control site were analyzed for selected HMs, i.e., Chromium (Cr), Lead (Pb), Nickel (Ni), Iron (Fe), and Zinc (Zn). The phytoremediation potential of plants was assessed using the bioaccumulation factor (BAF), bioaccumulation coefficient (BAC), and translocation factor (TF), while soil pollution levels were evaluated using the contamination factor (CF), geoaccumulation index (Igeo), enrichment factor (EF), potential ecological risk index (PERI), and human health risk indices. The results revealed that based on TF and BAC values, Alhagi maurorum Medic., Astragalus creticus Lam., Cichorium intybus L., Berberis lycium Royle, and Datura stramonium L. were hyperaccumulators for Cr while Parthenium hysterophorus L. was a promising species for both Ni and Cr. Similarly, CF values for Fe, Ni, Pb, and Cr were &gt;6, thereby showing very high contamination, while Igeo values for Fe, Ni, Pb, and Cr were (class 6, &gt;5), showing that the soil was extremely polluted. Furthermore, EF values for Fe, Ni, Pb, Cr, and Zn were 2 &lt; EF ≤ 5, depicting moderate enrichment, while PERI values were in the range of 91.31–195.84, employing moderate ecological risks (95 &lt; PERI &lt; 190) from the dumpsite’s soil. Moreover, for non-carcinogenic exposure, none of the analyzed metals exceeded the threshold limit HRI values &gt; 1 in both adults and children. Likewise, in the case of carcinogenic effects, the CRI values were lower than the tolerable limits (1 × 10−6–1 × 10−4) in both adults and children. Moreover, almost all studied plants could be utilized for the phytoextraction of mentioned HMs. In future, the present study can help in the implementation of public policies to ensure sustainability and developmental activities in contaminated sites. Based on these results, it is concluded that there is a dire need of monitoring solid waste dumpsites due to various types of potential risks associated with the contamination of HMs. Moreover, to minimize the potential health problems arising from the dumpsite, it is substantive that special attention should be paid to work on sustainable and eco-friendly remedial measures.

Specific lignin and cellulose depolymerization of sugarcane bagasse for maximum bioethanol production under optimal chemical fertilizer pretreatment with hemicellulose retention and liquid recycling

By screening out total nine sugarcane cultivars that contain directly-fermentable sugars, this study examined largely varied hexoses yields from direct enzymatic hydrolysis of bagasse residues. Using two representative sugarcane bagasse substrates, this study sorted out optimal K3PO4 pretreatments by performing classic response surface methodology, which respectively extracted 58% and 63% lignin and significantly reduced cellulose CrI and DP values in two pretreated bagasse residues. These consequently led to remarkably raised cellulose accessibility by 1.4- and 3.6 folds for near-complete biomass enzymatic saccharification with hexoses yields close to 100% (% cellulose). Notably, unlike physical (hot water, steam explosion) and chemical (acid, alkali) pretreatments as previously examined, this optimal pretreatment (6.4% K3PO4, 144.0 °C, 1 h) could not significantly extract arabinose-rich hemicellulose, suggesting that almost all xylose of hemicelluloses was applicable for engineered yeast co-fermentation to achieve maximum bioethanol at 29% (% dry matter) without the necessity of solid-liquid separation, water washing, and detoxification process. Furthermore, this study collected all K3PO4 liquid waste as chemical fertilizer into rice culture for much enhanced plant growth and biomass production up to 1.5 folds. Therefore, this work has proposed a mechanism model to highlight a cost-effective and green-like strategy for high yield of bioethanol with potential value-added bioproducts by using sugarcane bagasse and other lignocellulose residues.

Tuning the properties of pineapple peel cellulose nanofibrils by TEMPO-mediated oxidation and ball milling

In this study, the oxidized cellulose nanofibrils from pineapple peel (PP-TOCNF) were prepared by TEMPO-mediated oxidation followed by ball milling. The influence of oxidation degree on the structure and properties of PP-TOCNF were investigated, including Fourier transform infrared spectroscopy , X-ray diffraction, atomic force microscope (AFM), X-ray photoelectron spectroscopy and thermogravimetry, as well as the potential application in aerogels. The results suggested that TEMPO oxidation facilitated the dispersion of PP-TOCNF due to the strong electrostatic repulsion between –COO− groups. Regulating oxidation degree by varying NaClO concentration could effectively adjust the –COO− content (0.167–0.550 mmol/g), zeta potential (− 18 to − 34 mV) and rheological properties. The obtained PP-TOCNF showed a long fibrillar structure, whose average diameter and CrI values gradually decreased with the increase of oxidation degree. The PP-TOCNF-based aerogels exhibited a light weight, good porosity, water absorption, and mechanical properties, which also can be easily adjusted by oxidation degree of PP-TOCNF. Furthermore, TEMPO oxidation improved the stability and shape recovery ability of aerogels in water.Graphical abstract

Elucidating thermochemical pretreatment effectiveness of different particle-size switchgrass for cellulosic ethanol production

Effects of switchgrass particle sizes (<0.25 mm, 0.5–1.0 mm, and 2.0–4.0 mm) on the effectiveness of H2SO4 and NaOH pretreatments were investigated. As particle size increased, glucan, xylan, and lignin contents in raw switchgrass augmented from 30.32% to 32.02%, 18.44% to 19.03%, and 14.78% to 15.33%, respectively. Glucan and xylan (58.54–60.94% and 18.55–20.01%) contents in NaOH pretreated switchgrass and their recoveries (91.95–94.69% and 47.91–52.31%) increased. The highest glucan content (55.76%) and recovery (79.72%) in H2SO4 pretreated switchgrass were reached by middle particle size. The lowest (59.39% for H2SO4 and 58.99% for NaOH) and highest (65.23% for H2SO4 and 66.15% for NaOH) CrI values were obtained from middle and small particle sizes, respectively. SEM images and FTIR spectra showed no visible variations in microstructures and chemical bonds among different particle sizes under the same pretreatment conditions. On the basis of pretreated switchgrass, the highest ethanol concentration and efficiency were reached by big particle size for H2SO4 pretreated (7.03 g/L and 49.28%) switchgrass, while they were achieved by small particle size for NaOH pretreated (11.68 g/L and 72.37%) switchgrass. The highest ethanol yield based on raw switchgrass was attained by big particle size for untreated (29.54%), middle particle size for H2SO4 pretreated (30.60%), and small particle size for NaOH pretreated (62.36%) switchgrass. These findings indicate that the optimal ethanol conversion performance is the result of the interaction between the pretreatment method and biomass particle size.

Ultra-stable Eu3+/Dy3+ co-doped CsPbBr3 quantum dot glass nanocomposites with tunable luminescence properties for phosphor-free WLED applications

Colloidal CsPbBr3 perovskite quantum dots (PQDs) have substantially improved modern optoelectronic applications, including solid-state lighting, thanks to their highly pure and intense green light emission. However, some drawbacks including lead toxicity, poor stability, and difficulties in emission color tuning hinder their practical applications. Herein, ultra-stable Eu3+/Dy3+ co-doped CsPbBr3 PQD glass nanocomposites (GNCs) with tunable color emissions from green to red and then white are synthesized via melt-quenching followed by heat-treatment method to be used in white light-emitting diodes (WLEDs). Eu3+ and Dy3+ ions are selected to overcome the color tunability obstacle of PQDs and to obtain phosphor-free white light emission with enhanced CRI values. The photoluminescent performance of GNCs is shown to be reversible at elevated temperatures and remains stable even in water. Ultimately, a prototype WLED is constructed by coupling a selected Eu3+/Dy3+ co-doped CsPbBr3 PQD GNC on top of a 400 nm-emitting LED chip to demonstrate its superior optical performance with a color rendering index of 78 and correlated color temperature of 5436 K. The developed GNCs with long-term stability, and excellent tunable luminescent properties may overcome the commercialization barriers of CsPbBr3 PQDs for WLED applications.

Structure and emission properties of P2O5–Na2O–Pb3O4-MO, (MO = SrO, Y2O3, MoO3, Ag2O, CdO and SnO) glass and glass ceramics

A group of glass and glass ceramic solids with compositions of 70%P2O5–20%Na2O–9%Pb3O4–1%MO, where MO refers to SrO, Y2O3, MoO3, Ag2O, CdO and SnO were prepared by rapid quenching from molten state. The random environment of all obtained samples was verified by X-ray diffraction. Several phosphate groups and bands in addition to the presence of P–O-M and M-O-M linkages are evidenced by IR spectroscopy. The density and molar volume values of the studied samples were found to depend on the relative constituent dopant molecules and the experimental values are found to exhibit approximately the same behavior as the theoretically obtained values. The characteristic temperatures are also studied by the DTA analysis, where the thermal constancy of the samples is showed to grow up with moving rightward in the periodic table from Sr to Sn ion. All the samples are found to be of the diamagnetic type, with a major magnetic effect played by the Na+ ions. The studied samples are found to emit light with different colors when excited by a light with 365 nm wavelength. The obtained CCT, CRI and LER values nominates the present glasses to be involved in manufacturing solid state light sources for high cool light applications.

Concentration dependent luminescence, energy transfer and Judd- Ofelt analysis of single composition white light emitting NaCa2Mg2V3O12: XEu3+ phosphor

Near- UV-activated NaCa2Mg2V3O12: X Eu3+phosphors were synthesized by conventional solid state reaction method and the structural and luminescent properties were studied in detail. The XRD patterns reveal their cubic structure with Ia 3‾ d (230) space group and the excitation spectra exhibited the broad and intense absorption in the near UV region. The undoped host was effectively excited under 342 nm to get a blue-green emission whereas characteristic Eu3+ emission along with host emission was observed in the Eu3+ doped NaCa2Mg2V3O12 phosphors. Here VO43− group absorbs and transfers energy to the Eu3+ions there by acting as sensitizers. The quadrupole-quadrupole interactions responsible for multipolar interactions along with decay curves were used to confirm the energy transfer process. The Judd- Ofelt analysis was performed to evaluate the various radiative properties of the synthesized phosphors. The thermal stability of the sample was evaluated and found to be very promising. Quantum yield of the white light emitting NaCa2Mg2V3O12: 0.08Eu3+ phosphor was measured and the value is found to be 46.11% and the life time of the 5D0 excited state was 0.4358 ms. The CIE coordinate (0.3086, 0.3517) and CRI (82) values corresponding to the optimum concentration sample proves the prepared phosphor to be promising for various optoelectronic applications.

Narrow-Band Red-Emitting Phosphors with High Color Purity, Trifling Thermal and Concentration Quenching for Hybrid White LEDs and Li3Y3BaSr(MoO4)8:Sm3+, Eu3+-Based Deep-Red LEDs for Plant Growth Applications.

Trivalent europium-based monochromatic red light-emitting phosphors are an essential component to realize high-performance smart lighting devices; however, the concentration and thermal quenching restrict their usage. Here, we report a series of efficient Eu3+-substituted Li3Y3BaSr(MoO4)8 red-emitting phosphors based on a stratified scheelite structure with negligible concentration and thermal quenching. All of the host and phosphor compositions crystallize in monoclinic crystal structure (space group C2/c). All of the phosphor compositions produce narrow-band red emission (FWHM ∼6 nm), which is highly apparent to the human eyes, and lead to exceptional chromatic saturation of the red spectral window. Concurrently, detailed investigations were carried out to comprehend the concentration and thermal quenching mechanism. Absolute quantum yields as high as 88.5% were obtained for Li3Y0.3Eu2.7BaSr(MoO4)8 phosphor with virtuous thermal stability (at 400 K, retaining 87% of its emission intensity). The light-emitting diodes were constructed by coupling Li3BaSrY0.3Eu2.7(MoO4)8 red phosphor with a near-UV LED chip (395 nm) operated at 20 mA forward bias, and the hybrid white LED (an organic yellow dye + red Li3Y3BaSr(MoO4)8:Eu3+ phosphor integrated with an NUV LED chip) showed a low CCT (6645 K), high CRI (83) values, and CIE values of x = 0.303; y = 0.368, which indicated that the synthesized phosphors can be a suitable red component for white LEDs. In addition, we have systematically investigated the Sm3+ and Sm3+, Eu3+ activation in Li3Y3BaSr(MoO4)8 to display the latent use of the system in plant growth applications and establish that the phosphor exhibits orange red emission with an intense deep-red emission (645 nm (4G5/2 → 6H9/2)). The phytochrome (Pr) absorption spectrum well matched the fabricated deep-red LED (by integrating a NUV LED + Li3Y3BaSr(MoO4)8:Sm3+ and Eu3+ phosphor) spectral lines.

Efficient and ultra-thermally stable Eu3+ and Sm3+-activated narrow-band red/deep red-emitting phosphors and their versatile applications.

A succession of Eu3+-activated Na2Y4(WO4)7 (NYW) red phosphors were synthesised and their optical properties were studied in detail for white LED, latent fingerprint and plant growth applications. The phosphors crystallised in a tetragonal system with space group I41/a. The NYW:Eu3+ red phosphors demonstrated a line-like emission at 616 nm owing to electric dipole transition, and a systematic concentration-dependent PL study revealed that concentration quenching occurs at x = 1.8 with a color purity of 96.06%. The thermal stability and internal quantum efficiency of the phosphor were found to be ∼75.54% (at 423 K) and 88%, respectively. Furthermore, solid solution phosphors were synthesized to increase QE, which was found to be 91.27%. Specifically, the hybrid white LED exhibits warm white light with high CRI (80) and low CCT (5730 K) values, and these values are further improved (CRI-81, CCT-4274 K) when the WLED is fabricated using the most efficient solid solution phosphor Na2Y2.2Eu1.8(WO4)3(MoO4)4. The currently synthesized phosphors can be potential candidates for security applications. The selected phosphor compositions can be used for the detection of latent fingerprints. Besides, a succession of Eu3+ and Sm3+ co-doped phosphors were synthesized and their photophysical properties were studied systematically. The deep red LED was fabricated using the same and this could be a possible light source for plant growth usage.