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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Synthesis and photoluminescence properties of Dy{sup 3+} doped white light emitting CdTa{sub 2}O{sub 6} phosphors

The undoped and CdTa{sub 2}O{sub 6}:Dy{sup 3+} (0.2≤x≤2.0 mol%) phosphors were synthesized at 1100 °C for 12 h by the conventional solid state reaction method. The synthesized CdTa{sub 2}O{sub 6}:Dy{sup 3+} phosphors were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and Photoluminescence (PL) analyses. The PL spectra showed the presence of excitation peaks between 310 and 440 nm due to the 4f–4f transitions of Dy{sup 3+}. The emission of Dy{sup 3+} ions at 353.0 nm excitation was observed at 487.1 nm (blue) and 577.8 nm (yellow) due to the {sup 4}F{sub 9/2}→{sup 6}H{sub 15/2} transitions and {sup 4}F{sub 9/2}→{sup 6}H{sub 13/2} transitions, respectively. The PL analysis results also showed that the emissions increase with the increasing Dy{sup 3+} ion content. The emissions increased with the doping concentration of up to 1 mol%, and above this level decreased due to concentration quenching effect. The CIE chromaticity color coordinates (x,y) of the CdTa{sub 2}O{sub 6}:Dy{sup 3+} phosphors were found to be in the white light region of the chromaticity diagram. - Graphical abstract: Emission spectra at λ{sub ex}=353.0 nm and CIE chromaticity coordinate diagram of CdTa{sub 2}O{sub 6}:Dy{sup 3+} phosphors. - Highlights: • Pure and CdTa{sub 2}O{sub 6}:Dy{sup 3+} was produced by solid state reaction method. • CdTa{sub 2}O{sub 6}:Dy{sup 3+} phosphor exhibited blue and yellow emissions due to the {sup 4}F{sub 9/2}→{sup 6}H{sub 15/2} and {sup 4}F{sub 9/2}→{sup 6}H{sub 13/2} transitions. • The CCT value for 1.0 mol% CdTa{sub 2}O{sub 6}:Dy{sup 3+} was 5133 K which was located in the cool white daylight region. • Dy{sup 3+} doped CdTa{sub 2}O{sub 6} phosphor has potential in the production of white LEDs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Red phosphor Ca{sub 2}Ge{sub 7}O{sub 16}:Eu{sup 3+} for potential application in field emission displays and white light-emitting diodes

Abstract: A novel red emitting phosphor of Eu{sup 3+} doped Ca{sub 2}Ge{sub 7}O{sub 16} was prepared through the solid state reaction. The luminescence properties were studied in detail by photoluminescence excitation (PLE), emission (PL) spectra and cathodoluminescence (CL). Under the excitation of ultraviolet light, Ca{sub 2}Ge{sub 7}O{sub 16}:Eu{sup 3+} phosphor shows the characteristic {sup 5}D{sub 0}-{sup 7}F{sub J}(J = 1, 2, 3, 4) transition of Eu{sup 3+} with two different emissions due to the two kinds of Eu{sup 3+} ions. The luminescent intensity could be improved by co-doping with the charge compensators R{sup +} (Li, Na, K) which partially substitute for Ca{sup 2+} crystal sites. CL spectra show that Eu{sup 3+} ions were excited by the plasma produced by the incident electrons and the CL properties of Ca{sub 2}Ge{sub 7}O{sub 16}:Eu{sup 3+}, Li{sup +} as a function of accelerating voltage and probe current were investigated. Ca{sub 2}Ge{sub 7}O{sub 16}:Eu{sup 3+} phosphor offers higher thermal stability compared with the commercial red phosphor Y{sub 2}O{sub 3}:Eu{sup 3+}. The results indicate that Ca{sub 2}Ge{sub 7}O{sub 16}:Eu{sup 3+} can be a suitable red-emitting phosphor candidate for FEDs and w-LEDs.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A novel orange-red emitting NaCaVO{sub 4}:Sm{sup 3+} phosphor for solid state lighting

The samarium doped NaCaVO{sub 4} phosphor was synthesized by the combustion method. The X-ray powder diffraction (XRD) analysis confirmed that the phosphor powder crystallized as orthorhombic structure belonging to space group Cmcm. From Williamson-Hall analysis the grain size and microstrain in the powder was estimated. The Fourier- transform infrared (FT-IR) studies further validated the formation of vanadate phase of the phosphor. Photoluminescence (PL) study revealed that the phosphor could be efficiently excited by UV-VIS from 200 nm to 500 nm. The 565 nm, 602 nm, 648 nm and 713 nm emissions were ascribed to {sup 4}G{sub 5/2} to {sup 6}H{sub J} (J = 5/2, 7/2, 9/2 and 11/2) transitions of the Sm{sup 3+} ion. The present material may be explored as a novel phosphor to be excited by UV light emitting diodes (LEDs) chips for solid-state lighting and display applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Luminescent properties of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} and its luminescence improvement by incorporating A{sup +} (A=Li, Na, and K)

A novel green phosphor SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} is synthesized by a high temperature solid-state method, and its luminescent property is investigated. X-ray diffraction patterns of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} indicate a similarity crystalline phase to SrZn{sub 2}(PO{sub 4}){sub 2}. SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} shows green emission under 369 nm excitation, and the prominent luminescence in green (544 nm) due to {sup 5}D{sub 4}–{sup 7}F{sub 5} transition of Tb{sup 3+}. For the 544 nm emission, excitation spectrum has several excitation band from 200 nm to 400 nm. Emission intensity of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} is influenced by Tb{sup 3+} concentration, and concentration quenching effect of Tb{sup 3+} in SrZn{sub 2}(PO{sub 4}){sub 2} is also observed. With incorporating A{sup +} (A=Li, Na, and K) as compensator charge, the emission intensity of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} can be obviously enhanced. CIE color coordinates of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} locate in the green region. The results indicate this phosphor may be a potential application in white LEDs. - Graphical abstract: SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} can produce green emission under near-UV excitation, and its luminescent properties can be improved by incorporating A{sup +} (A=Li, Na, and K). - Highlights: • SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} can produce green emission under near-UV excitation. • Concentration quenching effect of Tb{sup 3+} in SrZn{sub 2}(PO{sub 4}){sub 2} is observed. • Emission intensities of SrZn{sub 2}(PO{sub 4}){sub 2}:Tb{sup 3+} are enhanced by codoped A{sup +} (A=Li, Na, K)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Two-step synthesis of a novel red-emitting Ba2ZrF8:Mn4+ phosphor for warm white light-emitting diodes

Highlights: • A novel red-emitting Ba{sub 2}ZrF{sub 8}:Mn{sup 4+} was prepared by two-step method at low temperature. • The phosphor shows an intense red emission under 460 nm excitation matching well with blue LED chip. • The energy transfer between Mn{sup 4+} was confirmed to be electric dipole-quadrupole interaction. - Abstract: A novel red-emitting Ba{sub 2}ZrF{sub 8}: Mn{sup 4+} phosphor was prepared by two-step method at low temperature, where critical precursor K{sub 2}MnF{sub 6} was prepared first by the reduction of KMnO{sub 4} using H{sub 2}O2 as reducer. The crystal structure and morphology of the phosphor was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), showing single phase product. Luminescent properties of the phosphor were investigated by photoluminescence spectroscopy (PL) and decay curves. The molar ratio of KMnO{sub 4}: KHF{sub 2} was confirmed to play the key role in improving the luminous efficiency. More importantly, the phosphor exhibits a broadband excitation from 300 to 520 nm due to {sup 4}A{sub 2g}→{sup 4}T{sub 1g} and {sup 4}A{sub 2g}→{sup 4}T{sub 2g} transition of Mn{sup 4+}, matching well with blue LED chips. Under 465 nm excitation, intense red emission at around 630 nm with high color purity is achieved, suggesting the red-emitting phosphor has great potential for white light-emitting diodes (wLEDs).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Facile synthesis of Ca{sub 0.68}Si{sub 9}Al{sub 3}(ON){sub 16}:Eu{sup 2+} microbelts mat with the enhanced fluorescence and mechanical performance

Yellow-emitting phosphor mat consisting of Ca{sub 0.68}Si{sub 9}Al{sub 3}(ON){sub 16}:Eu{sup 2+} microbelts was prepared by electrospinning and subsequent nitridation. The as-prepared fiber precursor is smooth and uniform with diameter of 800 to 900 nm. After removing organic templates and nitridation, the morphology of the fiber is well retained and thus a smooth microbelts phosphor mat was obtained. X-ray diffraction and the photoluminescence (PL) spectra reveals that a relatively pure Ca{sub 0.68}Si{sub 9}Al{sub 3}(ON){sub 16} phase and the highest spectral intensity could be obtained at a relatively low temperature of 1500 °C and Eu{sup 2+} doping molar concentration of 0.1. The excitation spectra exhibits a broad band, ranging from 300 to 550 nm, which could be excited by blue LED chip at room temperature. The emission spectra of all exhibits a single broad band in the 400 to 700 nm region, with the maximum intensity always being at 580 nm. The Ca{sub 0.68}Si{sub 9}Al{sub 3}(ON){sub 16}:Eu{sup 2+} microbelts phosphor mat has the bending strength about 4.5 MPa with a photoluminescence quantum yield as high as 65%. By employing it as yellow phosphor, a high-performance warm white LED could be fabricated with low correlated color temperature (2985 K), high-color-rendering index (Ra=86) and luminous efficacy of 129.5 lm W{sup −1}. Different color temperatures also could be tuned by employing microbelts phosphor mats with different thicknesses. - Graphical abstract: Yellow-emitting phosphor mat consisting of Ca{sub 0.68}Si{sub 9}Al{sub 3}(ON){sub 16}:Eu{sup 2+} microbelts fibers were prepared by electrospinning the fiber precursor and subsequent nitridation. Because the good mechanical strength it could be utilized to realize LEDs remote packaging. By employing it as yellow phosphor, a high-performance warm white LED could be fabricated. Different color temperatures also could be tuned by employing microbelts phosphor mats with different thicknesses. - Highlights: • Ca{sub 0.68}Si{sub 9}Al{sub 3}(ON){sub 16}:Eu{sup 2+} microbelts mats were synthesized by electrospinning method. • The optimum doping concentration of Eu{sup 2+} ion is 0.1 mole. • The microbelts mats show strong yellow emission at 580 nm. • The Ca{sub 0.68}Si{sub 9}Al{sub 3}(ON){sub 16}:Eu{sup 2+} mat had the bending strength about 4.5 Mp. • Different color temperatures could be turned with different thicknesses of the mats.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Mn4+/Zn2+:YAG glass ceramic for light emitting devices

Highlights: • Luminescence of Mn{sup 4+}:YAG red phosphor was enhanced via Zn{sup 2+} doping. • Mn{sup 4+}/Zn{sup 2+}:YAG GC was successfully prepared via one-step low temperature co-sintering technique. • A series of lighting device was achieved by coupling the Mn{sup 4+}/Zn{sup 2+}:YAG GC with the commercial blue chips and Ce{sup 3+}:LuAG GC. - Abstract: The rare-earth-free Mn{sup 4+}-activated oxide red phosphors draw great attention for their potential applications in the field of light-emitting diodes (LEDs). In this work, the red-emitting Mn{sup 4+}/Zn{sup 2+}:Y{sub 3}Al{sub 5}O{sub 12} phosphor, showing strong red emission peaked at ∼ 672 nm as a result of the spin-forbidden {sup 2}E{sub 2g} → {sup 4}A{sub 2g} electron transition of Mn{sup 4+} ions under 478 nm excitation, was synthesized by a traditional solid-state reaction route in air. The microstructure and luminescent performance of this red-emission phosphor was investigated in detail. From the experimentally measured spectroscopic data, the crystal field strength (Dq) and the Racah parameters B and C were calculated, respectively. In addition, Zn{sup 2+} dopant was found to be beneficial for enhancing Mn{sup 4+} luminescence. Subsequently, Mn{sup 4+}/Zn{sup 2+}:YAG glass ceramic was successfully prepared via using Mn{sup 4+}/Zn{sup 2+}:YAG phosphors incorporated into tellurate glass. A tunable lighting device was successfully achieved by coupling the red-emitting Mn{sup 4+}/Zn{sup 2+}:YAG GC with the commercial blue chips and Ce{sup 3+}:Lu{sub 3}Al{sub 5}O{sub 12} GC.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

High-Performance Blue-Excitable Yellow Phosphor Obtained from an Activated Solvochromic Bismuth-Fluorophore Metal–Organic Framework

Here, we report the synthesis, structure, and photoluminescence properties of a new bismuth based luminescent metal-organic framework (LMOF). The framework is comprised of a 9-coordinated Bi 3+ building unit and 4', 4''', 4''''', 4'''''''-(ethene-1,1,2,2-tetrayl)tetrakis([1,1'-biphenyl]-4-carboxylic acid) (H 4 tcbpe) organic linker, which has strong yellow aggregation induced emission (AIE). The structure can be viewed as two interpenetrated 4,4-anionic nets that are stabilized by K + ions forming one-dimensional helical inorganic chains by connecting bismuth nodes through shared oxygen bonds. The as-made LMOF has a bluish emission centered at 459 nm with an internal quantum yield of 57% when excited at 360 nm. The emission properties of the LMOF were found to be highly solvochromic with respect to DMF. Upon partial solvent removal, the framework undergoes significant red-shifting to a greenish emission centered at 500 nm. Complete removal of DMF results in additional red-shifting fluorescence coupled with structural changes. The resulting material has strong blue-excitable (455 nm) yellow emission centered at 553 nm, with a quantum yield of 74%, which is maintained after heating in air for 5 days at 90°C. This is the second highest quantum yield value for blue-excited yellow emission among all reported LMOFs.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Synthesis, structural and optical properties of BaMoO{sub 4}:Eu{sup 3+} shuttle like phosphors

Graphical abstract: - Highlights: • BaMoO{sub 4}:Eu{sup 3+} phosphors were synthesized by a facile synthesis route. • PL and CL spectra showed dominant emissions due to ({sup 5}D{sub 0} → {sup 7}F{sub 2}) hypersensitive transitions. • The excitation wavelengths in the UV-B region make BaMoO{sub 4}:Eu{sup 3+} phosphors as a good candidate in the red region for the development of UV-based white LEDs. • PL and CL spectra showed similar CIE values close to the commercially available Y{sub 2}O{sub 3}:Eu{sup 3+} phosphors. - Abstract: Eu{sup 3+} ions doped BaMoO{sub 4} phosphor samples were synthesized by a facile synthesis process. The tetragonal phase of the host lattice was substantiated by the X-ray diffraction patterns. The morphological studies were carried out by taking the scanning electron microscope and transmission electron microscope images and confirmed the formation of shuttle like particles with perpendicular protrusions in the middle of the particle. The single crystalline nature of the phosphors was confirmed by the selected area electron diffraction pattern. The photoluminescence (PL) properties of the Eu{sup 3+} ions doped samples revealed good emission with a high asymmetry ratio when excited with ultraviolet B wavelengths (between 280 and 315 nm). The cathodoluminescence (CL) spectra showed similar results to the PL spectra. The calculated CIE values based on the PL and CL spectra were almost similar and confirmed the rich red emission.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Simple coating synthesis and enhanced luminescence behaviour of LiLa(MoO4)2:Eu3+@NaF

Highlights: • LiLa(MoO{sub 4}){sub 2}:Eu{sup 3+}{sub 0.06} @ (NaF){sub y wt} were synthesized with a simple coating method. • PL intensity can be enhanced as high as 4.80 times by coating NaF. • Enhancement PL intensity is a major effect, and increasing R is a minor effect. • LiLa(MoO{sub 4}){sub 2}:Eu{sup 3+}{sub 0.06} @ (NaF){sub 0.025 wt} was a phosphor with high R values (R = 5.89). - Abstract: A series of LiLa(MoO{sub 4}){sub 2}:Eu{sup 3+}@ (NaF){sub y wt} were prepared with a simple coating method. XRD results confirm that NaF coating will cause the slight expand of the lattice volume for the sample. Strongly enhanced emission effect inducing by NaF coating is observed. The emission spectra (PL) intensity of the optimal sample, LiLa(MoO{sub 4}){sub 2}:Eu{sup 3+}{sub 0.06} @ (NaF){sub 0.025wt} is as high as 4.8 times of that of LiLa(MoO{sub 4}){sub 2}:Eu{sup 3+}{sub 0.06}. Furthermore, dual emission properties inducing by NaF coating are observed. Enhancement emission of Eu{sup 3+} is a major effect, and increasing R is a minor effect. The optimal coating content of NaF is 2.5 wt%, which the corresponding chromaticity coordinates excited at 465 nm is x = 0.6650, y = 0.3347, which is nearly as same as the NTSC (National Television Standard Committee) standard values for red (x = 0.67, y = 0.33). So, it is a potential red-emitting phosphor with high R values (R = 5.89) for blue light-based white LED.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

The site occupation and valence of Mn ions in the crystal lattice of Sr{sub 4}Al{sub 14}O{sub 25} and its deep red emission for high color-rendering white light-emitting diodes

Highlights: • Different valences of Mn ions in Sr{sub 4}Al{sub 14}O{sub 25} were identified using XANES and EPR. • Red luminescence was attributed to Mn{sup 4+} occupying the center of AlO{sub 6} octahedron. • The Mn{sup 3+} incorporated in the center of AlO{sub 4} tetrahedron was non-luminescent. • The bond-valence theory was used to analyze the effective valences of cations. • A white LED device with CRI up to Ra 93.23 was packaged by using the red phosphor. - Abstract: The synthesis and component of red phosphor, Sr{sub 4}Al{sub 14}O{sub 25}: Mn, were optimized for application in white light-emitting diodes. The microstructure and morphology were investigated by the X-ray diffraction and scanning electron microscopy. Different valences of Mn ions in Sr{sub 4}Al{sub 14}O{sub 25} were discriminated using the electron paramagnetic resonance and X-ray absorption near-edge structure spectroscopy techniques. The bond-valence theory was used to analyze the effective valences of Sr{sup 2+} and Al{sup 3+} in Sr{sub 4}Al{sub 14}O{sub 25}. As a result, the strong covalence of Al{sup 3+} in the AlO{sub 4} tetrahedron other than in the AlO{sub 6} octahedron is disclosed. The deep red emission is attributed to Mn{sup 4+} occupying the center of AlO{sub 6} octahedron. The mechanism of energy transfer is mainly through dipole–dipole interaction, revealed by the analyses of critical distance and concentration quench. A high color rendering white LED prototype with color-rendering index up to Ra 93.23 packaged by using the red phosphor demonstrates its applicability.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Preparation and luminescence properties of phosphors of rare earth complexes based on polyoxotungstates

Highlights: • Three new phosphors of rare earth complexes based on polyoxotungstates were synthesized. • [Eu(PW{sub 11}O{sub 39}){sub 2}]{sup 11−} (1) emits red light which used as potential red light materials. • [Sm(PW{sub 11}O{sub 39}){sub 2}] {sup 11−} (2) emits strong orange-red light at 598.7 nm. • [Dy(PW{sub 11}O{sub 39}){sub 2}] {sup 11−} (3) emits white light which used as potential white light materials. - Abstract: Three new phosphors of rare earth complexes based on polyoxotungstates, K{sub 3}Cs{sub 8}[Eu(PW{sub 11}O{sub 39}){sub 2}]·11H{sub 2}O (1), K{sub 3}Cs{sub 8}[Sm(PW{sub 11}O{sub 39}){sub 2}]·10H{sub 2}O (2), and K{sub 5}Cs{sub 6}[Dy(PW{sub 11}O{sub 39}){sub 2}]·15H{sub 2}O (3) have been prepared and characterized. The crystallographic analyses reveal that these compounds consist of two monovacant keggin anions [PW{sub 11}O{sub 39}]{sup 7−} connected by a rare earth ion in a sandwich structure. The investigations of photoluminescence properties show that phosphor 1 emits strong red light at 614 and 702 nm, 2 emits strong orange-red light at 598.7 nm, and 3 exists two strong emissions at 479 nm (blue) and 574 nm (orange). The luminescence properties suggest that the 1 can be applied as the potential red-emitting crystal phosphor, and the 3 may be regarded as a potential white light material for LEDs.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Controllable synthesis and tunable luminescence of glass ceramic containing Mn{sup 2+}:ZnAl{sub 2}O{sub 4} and Pr{sup 3+}:YF{sub 3} nano-crystals

Highlights: • Glass ceramic containing ZnAl{sub 2}O{sub 4} and YF{sub 3} nano-crystals is fabricated. • Mn{sup 2+} and Pr{sup 3+} are selectively incorporated into ZnAl{sub 2}O{sub 4} and YF{sub 3}, respectively. • The luminescence color can be tuned by adjusting the excitation wavelength. - Abstract: Glass ceramic containing spinel ZnAl{sub 2}O{sub 4}:Mn{sup 2+} and orthorhombic YF{sub 3}:Pr{sup 3+} nano-crystals has been successfully prepared by a melt-quenching technique. X-ray diffraction and transmission electron microscopy demonstrated that two nano-phases, i.e. ZnAl{sub 2}O{sub 4} and YF{sub 3}, were homogeneously distributed among the glass matrix. Importantly, the selective incorporation of Pr{sup 3+} ions into the Y{sup 3+} nine-fold coordinated sites of YF{sub 3} and the segregation of Mn{sup 2+} dopants in the Zn{sup 2+} tetrahedral sites of ZnAl{sub 2}O{sub 4} were confirmed based on the excitation/emission spectra and the crystal field calculation. Under blue light excitation, both Pr{sup 3+} and Mn{sup 2+} in the glass ceramic can be simultaneously excited, and emit red and green luminescence, respectively, owing to the suppression of energy transfer between them. The luminescence color of the obtained glass ceramic can be easily tuned by adjusting the excitation wavelength. These results indicate the potential application of the glass ceramic as converting phosphor to generate white-light after coupling with the blue LED chip.

36 MATERIALS SCIENCE↗
NASA NTRS2016

Comparative Study of Lettuce and Radish Grown Under Red and Blue LEDs and White Fluorescent Lamps

Growing vegetable crops in space will be an essential part of sustaining astronauts during long-range missions. To drive photosynthesis, red and blue light-emitting diodes (LEDs) have attracted attention because of their efficiency, longevity, small size, and safety. In efforts to optimize crop yield, there is also recent interest in analyzing the subtle effects of additional wavelengths on plant growth. For instance, since plants often look purplish gray under red and blue LEDs, the addition of green light allows easy recognition of disease and the assessment of plant health status. However, it is important to know if wavelengths outside the traditional red and blue wavebands have a direct effect on enhancing or hindering the mechanisms involved in plant growth. In this experiment, a comparative study was performed on two short cycle crops of red romaine lettuce (Lactuca sativa cv. "Outredgeous") and radish (Raphanus sativa cv. 'Cherry Bomb'), which were grown under two light treatments. The first treatment being red (630 nm) and blue (450 nm) LEDs alone, while the second treatment consisted of daylight tri-phosphor fluorescent lamps (CCT approximately 5000 K) at equal photosynthetic photon flux (PPF). The treatment effects were evaluated by measuring the fresh biomass produced, plant morphology and leaf dimensions, leaf chlorophyll content, and adenosine triphosphate (ATP) within plant leaf/storage root tissues.

Food Production↗
DOE OSTI2013

Recovery of uranium from phosphoric acid medium by polymeric composite beads encapsulating organophosphorus extractants

The present study deals with the preparation and evaluation of the poly-ethersulfone (PES) based composite beads encapsulating synergistic mixture of D2EHPA and Cyanex 923 (at 4:1 mole ratio) for the separation of uranium from phosphoric acid medium. SEM was used for the characterization of the composite materials. Addition of 1% PVA (polyvinyl alcohol) improved the internal morphology and porosity of the beads. Additionally, microscopic examination of the composite bead confirmed central coconut type cavity surrounded by porous polymer layer of the beads through which exchange of metal ions take place. Effect of various experimental variables including aqueous acidity, metal ion concentration in aqueous feed, concentration of organic extractant inside the beads, extractant to polymer ratio, liquid to solid (L/S) ratio and temperature on the extraction of uranium was studied. Increase in acidity (1-6 M), L/S ratio (1- 10), metal ion concentration (0.2-3 g/L U{sub 3}O{sub 8}) and polymer to extractant ratio (1:4 -1:10) led to decrease in extraction of uranium. At 5.5 M (comparable to wet process phosphoric acid concentration) the extraction of uranium was about 85% at L/S ratio 5. Increase in extractant concentration inside the bead resulted in enhanced extraction of metal ion. Increase in temperature in the range of 30 to 50 Celsius degrees increased the extraction, whereas further increase to 70 C degrees led to the decrease in extraction of uranium. Amongst various reagents tested, stripping of uranium was quantitative by 12% Na{sub 2}CO{sub 3} solution. Polymeric beads were found to be stable and reusable up-to 10 cycles of extraction/stripping. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2015

Luminescent properties of Eu{sup 2+}-doped BaGdF{sub 5} glass ceramics a potential blue phosphor for ultra-violet light-emitting diode

Eu{sup 2+} doped transparent oxyfluoride glass ceramics containing BaGdF{sub 5} nanocrystals were successfully fabricated by melt-quenching technique under a reductive atmosphere. The structure of the glass and glass ceramics were investigated by differential scanning calorimetry, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The luminescent properties were investigated by transmission, excitation, and emission spectra. The decay time of the Gd{sup 3+} ions at 312 nm excited with 275 nm were also investigated. The results of XRD and TEM indicated the existence of BaGdF5 nanocrystals in the transparent glass ceramics. The excitation spectra of Eu{sup 2+} doped glass ceramics showed an excellent overlap with the main emission region of an ultraviolet light-emitting diode (UV-LED). Compared with the as-made glass, the emission of glass ceramics is much stronger by a factor of increasing energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions, the energy transfer efficiency from Gd{sup 3+} to Eu{sup 2+} ions was discussed. In addition, the chromaticity coordinates of glass and glass ceramics specimens were also discussed, which indicated that the Eu{sup 2+} doped BaGdF{sub 5} glass ceramics may be used as a potential blue-emitting phosphor for UV-LED.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗