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DOE OSTI2020

3D printed transparent ceramic YAG laser rods: Matching the core-clad refractive index

Yttrium Aluminum Garnet (YAG) solid state laser gain media rods with an active Neodymium-doped core and an optically-clear cladding region were additively manufactured via direct-ink-writing (DIW), followed by sintering and hot isostatic pressing to form fully dense optical ceramics. Lutetium and Gadolinium were chosen as optically-inert co-doping ions in the clad to match the increase in refractive index caused by the Neodymium in the core. Additionally, either 11.6% Lutetium or 3.8% Gadolinium can be used to match the index change from 2% neodymium; however, differences in diffusion distances across the core-clad interface lead to large fluctuations in index in that region. These index fluctuations can be minimized either by matching dopants with similar diffusion distances, or by implementing a gradual gradient in the doping profile, possible through DIW, rather than a sharp compositional interface attainable via more standard fabrication methods. This improvement in index homogeneity resulted in a 40% improvement in lasing performance compared with that of a core-clad rod fabricated with a sharp interface between the doped and undoped regions.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Synthesis, characterization, and utility of trifluoroacetic acid lanthanide precursors for production of varied phase fluorinated lanthanide nanomaterials

The synthesis of a series of lanthanide trifluoroacetic acid (H-TFA) derivatives which contain only the TFA and its conjugate acid has been developed. From the reaction of Ln(N(SiMe 3 ) 2 ) 3 with an excess amount of H-TFA, the products were identified as: [Ln(μ-TFA) 3 (H-TFA) 2 ]n (Ln = Y, Ce, Sm, Eu, Gd, Tb, Dy), [Ln(μ-TFA) 3 (μ-H-TFA)] n ·solv (Ln·solv = Pr·2 H-TFA, H 3 O + , Ho·2py, Er·py, Yb·py, H-TFA), 3[H][(TFA)La(μ-TFA) 3 La(TFA)(μ-TFA) 2 (μ c -TFA) 2 ] n ½(H 2 O) ½(H 2 O, H-TFA) (La·½(H 2 O) ½(H 2 O, H-TFA)), [(k 2 -TFA)Nd(μ-TFA) 3 ] n ·H-py + (Nd·H-py + ), [(py) 2 Tm(μ-TFA) 3 ] n (Tm), or [Lu(μ-TFA) 4 Lu(μ-TFA) 3 ·H 3 O + ] n (Lu·H 3 O + ). Here, the majority of samples formed long chain polymers with 3 or 4 μ-TFA ligands. Tm was isolated with py coordinated to the metal, whereas Ho, Er, and Yb were isolated with py located within the lattice. Select samples from this set of compounds were used to generate nanomaterials under solvothermal (SOLVO) conditions using pyridine (py) or octylamine at 185 °C for 24 h. The SOLVO products were isolated as: (i) from py: La – fluocerite (LaF 3 , PDF 98-000-0214, R = 9.64%, 35(0) nm), Tb – terbium fluoride (TbF 3 , PDF 00-037-1487, R = 4.76%, 21(2) nm), Lu lutetium oxy fluoride (LuOF, PDF 00-052-0779, R = 8.24%, 8(2) nm); (ii) from octylamine: La – fluocerite/lanthanum oxide carbonate (LaF 3 , PDF 98-000-0214, R = 7.47%, 5(0) nm; La 2 O 2 (CO 3 ), PDF 01-070-5539, R = 12.32%, 12(0) nm), Tb – terbium oxy fluoride (TbOF, PDF 00-008-0230, R = 7.01%, 5(0) nm); Lu – lutetium oxide (Lu 2 O 3 , PDF 00-012-0728, R = 6.52%, 6(1) nm).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2017

Structural Effects of Lanthanide Dopants on Alumina

Lanthanide (Ln 3+ ) doping in alumina has shown great promise for stabilizing and promoting desirable phase formation to achieve optimized physical and chemical properties. However, doping alumina with Ln elements is generally accompanied by formation of new phases (i.e. LnAlO3, Ln2O3), and therefore inclusion of Ln-doping mechanisms for phase stabilization of the alumina lattice is indispensable. In this study, Ln-doping (400 ppm) of the alumina lattice crucially delays the onset of phase transformation and enables phase population control, which is achieved without the formation of new phases. The delay in phase transition (θ → α), and alteration of powder morphology, particle dimensions, and composition ratios between α- and θ-alumina phases are studied using a combination of solid state nuclear magnetic resonance, electron microscopy, digital scanning calorimetry, and high resolution X-ray diffraction with refinement fitting. Loading alumina with a sparse concentration of Ln-dopants suggests that the dopants reside in the vacant octahedral locations within the alumina lattice, where complete conversion into the thermodynamically stable α-domain is shown in dysprosium (Dy)- and lutetium (Lu)-doped alumina. This study opens up the potential to control the structure and phase composition of Ln-doped alumina for emerging applications.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Airborne Release Fractions from Surrogate Nuclear Waste Fires Containing Lanthanide Nitrates and Depleted Uranium Nitrate in 30% Tributyl Phosphate in Kerosene

Airborne contaminants from fires containing nuclear waste represent significant health hazards and shape the design and operation of nuclear facilities. Much of the data used to formulate DOE-HDBK-3010-94, “Airborne Release Fractions/Rates and Respirable Fractions for Nonreactor Nuclear Facilities,” from the U.S. Department of Energy, were taken over 40 years ago. The objectives of this study were to reproduce experiments from Pacific Northwest Laboratories conducted in June 1973 employing current aerosol measurement methods and instrumentation, develop an enhanced understanding of particulate formation and transport from fires containing nuclear waste, and provide modeling and experimental capabilities for updating current standards and practices in nuclear facilities. A special chamber was designed to conduct small fires containing 25 mL of flammable waste containing lutetium nitrate, ytterbium nitrate, or depleted uranium nitrate. Carbon soot aerosols showed aggregates of primary particles ranging from 20 to 60 nm in diameter. In scanning electron microscopy, ~200-nm spheroidal particles were also observed dispersed among the fractal aggregates. The 200-nm spherical particles were composed of metal phosphates. Airborne release fractions (ARFs) were characterized by leaching filter deposits and quantifying metal concentrations with mass spectrometry. The average mass-based ARF for 238 U experiments was 1.0 × 10 -3 with a standard deviation of 7.5 × 10 -4 . For the original experiments, DOE-HDBK-3010-94 states, “Uranium ARFs range from 2 × 10 -4 to 3 × 10 -3 , an uncertainty of approximately an order of magnitude.” Therefore, current measurements were consistent with DOE-HDBK-3010-94 values. ARF values for lutetium and ytterbium were approximately one to two orders of magnitude lower than 238 U. Furthermore, metal nitrate solubility may have varied with elemental composition and temperature, thereby affecting ARF values for uranium surrogates (Yb and Lu). In addition to ARF data, solution boiling temperatures and evaporation rates can also be deduced from experimental data.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2015

Comparative efficacy of 177 Lu and 90 Y for Anti-CD20 Pretargeted Radioimmunotherapy in Murine Lymphoma Xenograft Models

Purpose Pretargeted radioimmunotherapy (PRIT) is a multi-step method of selectively delivering high doses of radiotherapy to tumor cells while minimizing exposure to surrounding tissues. Yttrium-90 ( 90 Y) and lutetium-177 ( 177 Lu) are two of the most promising beta-particle emitting radionuclides used for radioimmunotherapy, which despite having similar chemistries differ distinctly in terms of radiophysical features. These differences may have important consequences for the absorbed dose to tumors and normal organs. Whereas 90 Y has been successfully applied in a number of preclinical and clinical radioimmunotherapy settings, there have been few published pretargeting studies with 177 Lu. We therefore compared the therapeutic potential of targeting either 90 Y or 177 Lu to human B-cell lymphoma xenografts in mice. Methods Parallel experiments evaluating the biodistribution, imaging, dosimetry, therapeutic efficacy, and toxicity were performed in female athymic nude mice bearing either Ramos (Burkitt lymphoma) or Granta (mantle cell lymphoma) xenografts, utilizing an anti-CD20 antibodystreptavidin conjugate (1F5-SA) and an 90 Y- or 177 Lu-labeled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-biotin second step reagent. Results The two radionuclides displayed comparable biodistributions in tumors and normal organs; however, the absorbed radiation dose delivered to tumor was more than twice as high for 90 Y (1.3 Gy/MBq) as for 177 Lu (0.6 Gy/MBq). More importantly, therapy with 90 Y-DOTAbiotin was dramatically more effective than with 177 Lu-DOTA-biotin, with 100% of Ramos xenograft-bearing mice cured with 37 MBq 90 Y, whereas 0% were cured using identical amounts of 177 Lu-DOTA-biotin. Similar results were observed in mice bearing Granta xenografts, with 80% of the mice cured with 90 Y-PRIT and 0% cured with 177 Lu-PRIT. Toxicities were comparable with both isotopes. Conclusion 90 Y was therapeutically superior to 177 Lu for streptavidin-biotin PRIT approaches in these human lymphoma xenograft models.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2026

Fast and bright scintillators for ultrafast materials dynamics using 4th generation synchrotron

We present recent advances in fast and bright scintillators for ultrafast X-ray phase contrast imaging of dynamic materials experiments at the upgraded Advanced Photon Source (APS-U), a fourth generation synchrotron. APS-U enables hard X-ray imaging at frame rates of at least 13 MHz (corresponding to 77 ns or shorter interframe intervals), creating a new need for scintillators with faster response and higher light output than lutetium yttrium oxyorthosilicate (LYSO). For indirect imaging and diffraction with ultrafast cameras, commercial lanthanum bromide (LaBr3) and cerium bromide (CeBr3) are promising candidates. These materials exhibit decay times approximately a factor of two shorter than LYSO (around 40 ns) and lutetium oxyorthosilicate (LSO), while maintaining comparable light yield per incident X-ray photon. However, their implementation at APS-U requires addressing several challenges, including material limitations due to hygroscopicity, efficient optical coupling to imaging systems, and high quantum efficiency for conversion of scintillation light, predominantly at wavelengths below 400 nm, into detectable electronic signals. We report results from material characterization, detector integration and packaging, and beamline experiments of materials with impact. In addition, emerging scintillator classes, including perovskites and high-entropy materials, are discussed as potential alternatives for next-generation ultrafast X-ray diagnostics.

Wang, Zhehui [Los Alamos] (ORCID:0000000178264063)↗

DOE OSTI2018

Spectroscopic and laser characteristics of ceramics based on Yb{sup 3+}-doped Lu{sub 2}O{sub 3}–Y{sub 2}O{sub 3} solid solution

We report on quasi-cw lasing at a wavelength of 1031 nm with a maximum power of 8 W and a slope efficiency of 32.3 % achieved in a thin-disk ceramic element based on ytterbium-doped solid solution of yttrium and lutetium sesquioxides. A sample of Yb : (Lu, Y){sub 2}O{sub 3} ceramics was fabricated by solid-state sintering of nanosized particles of a predetermined composition synthesised by laser ablation. The study of the spectral and luminescent characteristics of the obtained ceramics shows that partial substitution of Y{sup 3+} cations by Lu{sup 3+} cations broadens the absorption, luminescence, and laser spectra and shifts their peaks with respect to those of Yb:Y{sub 2}O{sub 3} ceramics. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2011

Effects of disorder and isotopic substitution in the specific heat and Raman scattering in LuB{sub 12}

Precision measurements of the specific heat and spectral intensity I({omega}) of Raman scattering for Lu{sup N}B{sub 12} single crystal samples with various boron isotopes (N = 10, 11, nat) have been performed at low and intermediate temperatures. A boson peak in the low-frequency part of the I({omega}) spectrum has been observed for the first time for lutetium dodecaboride at liquid nitrogen temperatures. It has been shown that low-temperature anomalies in the specific heat, along with the features of Raman spectra, can be interpreted in terms of the transition to a cageglass state at T* = 50-70 K, which appears when Lu{sup 3+} ions are displaced from the centrosymmetric position in cavities of a rigid covalent boron sublattice towards the randomly located boron vacancies. The concentrations of various two-level systems that correspond to two types of vibrational clusters with correlation lengths of 12-15 and 18-22 A, respectively, have been estimated. The vibrational density of states of LuB{sub 12} has been calculated from Raman spectra in the model of soft atomic potentials. An approach has been proposed to explain the dielectrization of the properties of the YbB{sub 12} compound at T < T*, as well as the features of the formation of magnetic structures in RB{sub 12} antiferromagnets (R = Tb, Dy, Ho, Er, Tm) and the suppression of superconductivity in LuB{sub 12}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2016

Prediction of B1 to B10 phase transition in LuN under pressure: An ab-initio investigation

Ab-initio total energy calculations have been performed in lutetium nitride (LuN) as a function of hydrostatic compression to understand the high pressure behavior of this compound. Our calculations predict a phase transition from ambient rocksalt type structure (B1 phase) to a tetragonal structure (B10 phase) at ~ 240 GPa. The phase transition has been identified as first order in nature with volume discontinuity of ~ 6%. The predicted high pressure phase has been found to be stable up to at least 400 GPa, the maximum pressure up to which calculations have been performed.Further, to substantiate the results of static lattice calculations analysis of lattice dynamic stability of B1 and B10 phase has been carried out at different pressures. Apart from this, we have analyzed the lattice dynamic stability CsCl type (B2) phase around the 240 GPa, the pressure reported for B1 to B2 transition in previous all-electron calculations by Gupta et al. 2013. We find that the B2 structure is lattice dynamically unstable at this pressure and remains unstable up to ~ 400 GPa, ruling out the possibility of B1 to B2 phase transition at least up to ~ 400 GPa. Further, the theoretically determined equation of state has been utilized to derive various physical quantities such as zero pressure equilibrium volume, bulk modulus, and pressure derivative of bulk modulus of B1 phase at ambient conditions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Development of a laser system of the laboratory AVLIS complex for producing isotopes and radionuclides

The use of atomic vapour laser isotope separation (AVLIS) for solving a number of urgent problems (formation of {sup 177}Lu radionuclides for medical applications, {sup 63}Ni radionuclides for betavoltaic power supplies and {sup 150}Nd isotope for searching for neutrinoless double β decay and neutrino mass) is considered. An efficient three-step scheme of photoionisation of neodymium atoms through the 50474-cm{sup −1} autoionising state with radiation wavelengths of the corresponding stages of λ{sub 1} = 6289.7 Å, λ{sub 2} = 5609.4 Å and λ{sub 3} = 5972.1 Å is developed. The average saturation intensity of the autoionising transition is ∼6 W cm{sup −2}, a value consistent with the characteristics of the previously developed photoionisation schemes for lutetium and nickel. A compact laser system for the technological AVLIS complex, designed to produce radionuclides and isotopes under laboratory conditions, is developed based on the experimental results. (laser applications and other topics in quantum electronics)

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2012

Use of internal scintillator radioactivity to calibrate DOI function of a PET detector with a dual-ended-scintillator readout

Purpose: Positron emission tomography (PET) detectors that use a dual-ended-scintillator readout to measure depth-of-interaction (DOI) must have an accurate DOI function to provide the relationship between DOI and signal ratios to be used for detector calibration and recalibration. In a previous study, the authors used a novel and simple method to accurately and quickly measure DOI function by irradiating the detector with an external uniform flood source; however, as a practical concern, implementing external uniform flood sources in an assembled PET system is technically challenging and expensive. In the current study, therefore, the authors investigated whether the same method could be used to acquire DOI function from scintillator-generated (i.e., internal) radiation. The authors also developed a method for calibrating the energy scale necessary to select the events within the desired energy window. Methods: The authors measured the DOI function of a PET detector with lutetium yttrium orthosilicate (LYSO) scintillators. Radiation events originating from the scintillators' internal Lu-176 beta decay were used to measure DOI functions which were then compared with those measured from both an external uniform flood source and an electronically collimated external point source. The authors conducted these studies with several scintillators of differing geometries (1.5 x 1.5 and 2.0 x 2.0 mm{sup 2} cross-section area and 20, 30, and 40 mm length) and various surface finishes (mirror-finishing, saw-cut rough, and other finishes in between), and in a prototype array. Results: All measured results using internal and external radiation sources showed excellent agreement in DOI function measurement. The mean difference among DOI values for all scintillators measured from internal and external radiation sources was less than 1.0 mm for different scintillator geometries and various surface finishes. Conclusions: The internal radioactivity of LYSO scintillators can be used to accurately measure DOI function in PET detectors, regardless of scintillator geometry or surface finish. Because an external radiation source is not needed, this method of DOI function measurement can be practically applied to individual PET detectors as well as assembled systems.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2012

Effects of scandium substitution on the crystal structure and luminescence properties of LuBO{sub 3}: Ce{sup 3+}

The calcite phase of LuBO{sub 3} and ScBO{sub 3} polycrystalline powders were synthesized by solid state reaction method, and the Lu{sub 1-x}Sc{sub x}BO{sub 3}:Ce (x=0.2, 0.5, 0.7) single crystals were grown by the Czochralski method. A large composition deviation between the initial polycrystalline powders and final single crystal was confirmed by electron probe micro-analysis. Raman spectroscopy revealed that moderate lattice disorder was induced by scandium substitution. However, based on the single crystal X-ray study, we finally concluded that the crystal structure of lutetium scandium orthoborate still crystallized in the rhombohedral system belonging to R3{sup -}c. Furthermore, the relationship between the energies of the five 5d levels of Ce{sup 3+} and the crystalline environment was revealed. The total redshift, total crystal field splitting, and centroid shift of Lu{sub 1-x}Sc{sub x}BO{sub 3}:Ce{sup 3+} were calculated based on their VUV excitation spectra. The variations trend of these observed spectroscopic parameters was in accordance with the predicted ones. - Graphical abstract: The crystal structure of Lu{sub 1-x}Sc{sub x}BO{sub 3}:Ce is rhombohedral system with R3{sup -}c space group. The relationship between the energies of the five Ce{sup 3+} 5d levels and the crystalline environment is established. Highlights: Black-Right-Pointing-Pointer Moderate lattice disorder is induced by scandium doping. Black-Right-Pointing-Pointer The crystal structure of Lu{sub 1-x}Sc{sub x}BO{sub 3}:Ce is rhombohedral system with R3{sup -}c space group. Black-Right-Pointing-Pointer Relationship between energies of Ce{sup 3+} 5d levels and crystalline environment is established. Black-Right-Pointing-Pointer The spectroscopic parameters are experimentally and theoretically calculated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Quasi-spherical LuBO{sub 3} nanoparticles: Synthesis, formation, and luminescence properties

Graphical abstract: Quasi-spherical LuBO3 nanoparticles have been prepared via a facile hydrothermal route. The possible growth mechanism and the luminescent properties of the as-prepared microcrystals have been discussed. - Highlights: • LuBO{sub 3} nanoparticles were prepared by a facile hydrothermal route. • The Eu{sup 3+} and Tb{sup 3+}-doped LuBO{sub 3} products show strong red and green emissions. • This method may be more widely applicable in the design of other rare-earth compounds. - Abstract: Quasi-spherical LuBO{sub 3} nanoparticles have been successfully synthesized by a designed hydrothermal conversion method. The Lu(OH)CO{sub 3} nanoparticles were first prepared by a simple homogeneous precipitation method. Subsequently, LuBO{sub 3} nanoparticles were synthesized at the expense of the Lu(OH)CO{sub 3} nanoparticles during a hydrothermal conversion process. The conversion process from the Lu(OH)CO{sub 3} precursor to LuBO{sub 3} nanoparticles was investigated by time-dependent experiments. Moreover, the as-obtained Eu{sup 3+} and Tb{sup 3+}-doped LuBO{sub 3} products show strong characteristic red and green emissions under ultraviolet excitation and low-voltage electron beam excitation, respectively. This work sheds some light on the knowledge of conversion of different kind of lutetium compounds, and the luminescent properties have potential applications in fluorescent lamps and field emission displays. More importantly, this simple method is expected to allow the large-scale production of other complex rare-earth compounds with controllable morphologies and sizes, and exploration of the morphology and photoluminescence properties.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Influence of annealing temperature on structural and optical properties of Lu{sub 2}O{sub 3}:Eu{sup 3+}, Tb{sup 3+} transparent films

Highlights: • Lu{sub 2}O{sub 3}:Eu{sup 3+}, Tb{sup 3+} films were synthesized by sol–gel and by dip-coating technique. • Effects of annealing treatment on structural and optical properties were studied. • Optogeometrical characteristics of synthesized films were analyzed. • X-ray diffraction results showed that Lu{sub 2}O{sub 3}:Eu{sup 3+}, Tb{sup 3+} crystallizes at 700 °C. • High reddish emission on transparent films with at least 1 μm thick was observed. - Abstract: High-optical quality Lu{sub 2}O{sub 3}:Eu{sup 3+} 5 mol%, X Tb{sup 3+} (X = 0–0.04 mol%) thin films were prepared by the sol–gel process and dip-coating technique. The procedure was as follows: lutetium, europium and terbium nitrates were used as precursors, and ethanol as a solvent. Etylenglycol (EG) was added as a sol stabilizer, and the pH was adjusted by acetic acid. After 10 dipping-cycles, followed by an annealing process (600–900 °C) for 1 h, transparent, smooth and crack-free films (ra = 8–9 nm) were formed. The X-ray diffraction (XRD) results showed crystallized films into the cubic structure at 800 °C. The ellipsometry results showed that the thickness of the films varied from 1 to 1.4 μm at 1000 and 600 °C, respectively. Finally, the films presented a typical Eu{sup 3+} red emission at 611 nm ({sup 5}D{sub 0} → {sup 7}F{sub 2}); furthermore, the effect of the Tb{sup 3+} content showed that the highest emission intensity corresponded to the lower Tb{sup 3+} content.

36 MATERIALS SCIENCE↗

DOE OSTI2019

99m Tc-, 90 Y-, and 177 Lu-Labeled Iron Oxide Nanoflowers Designed for Potential Use in Dual Magnetic Hyperthermia/Radionuclide Cancer Therapy and Diagnosis

Development of a complex based on iron oxide nanoparticles (IONPs) for diagnosis and dual magnetic hyperthermia/radionuclide cancer therapy accomplishing high yields of radiolabeling and great magnetic heat induction is still a challenge. We report here the synthesis of citric acid, poly(acrylic acid) (PAA) and poly(ethylene glycol) coated IONPs and their labeling with three radionuclides, namely, technetium (99mTc), yttrium (90Y), and lutetium (177Lu), aiming at potential use in cancer diagnosis and therapy. Polyol-synthesized IONPs are a flowerlike structure with 13.5 nm spherically shaped cores and 24.8 nm diameter. PAA-coated nanoparticles (PAA@IONP) showed the best characteristics such as easy radiolabeling with very high yields (>97.5%) with all three radionuclides, and excellent in vitro stabilities with less than 10% of radionuclides detaching after 24 h. Heating ability of PAA@IONP in an alternating external magnetic field showed intrinsic loss power value of 7.3 nH m2/kg, which is one of higher reported values. Additionally, PAA@IONP itself presented no significant cytotoxicity to the CT-26 cancer cells, reaching IC50 at 60 μg/mL. However, under the external magnetic field, they show hyperthermia-mediated cells killing, which correlated with the magnetic field strength and time of exposure. Since PAA@IONP are easy to prepare, biocompatible, and with excellent magnetic heat induction, these nanoparticles radiolabeled with high-energy beta emitters 90Y and 177Lu have valuable potential as agent for dual magnetic hyperthermia/radionuclide therapy, while radiolabeled with 99mTc could be used in diagnostic imaging. Copyright © 2019 American Chemical Society.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2012

Rapid Microwave Preparation of Highly Efficient Ce[superscript 3+]-Substituted Garnet Phosphors for Solid State White Lighting

Ce{sup 3+}-substituted aluminum garnet compounds of yttrium (Y{sub 3}Al{sub 5}O{sub 12}) and lutetium (Lu{sub 3}Al{sub 5}O{sub 12}) - both important compounds in the generation of (In,Ga)N-based solid state white lighting - have been prepared using a simple microwave heating technique involving the use of a microwave susceptor to provide the initial heat source. Carbon used as the susceptor additionally creates a reducing atmosphere around the sample that helps stabilize the desired luminescent compound. High quality, phase-pure materials are prepared within a fraction of the time and using a fraction of the energy required in a conventional ceramic preparation; the microwave technique allows for a reduction of about 95% in preparation time, making it possible to obtain phase pure, Ce{sup 3+}-substituted garnet compounds in under 20 min of reaction time. It is estimated that the overall reduction in energy compared with ceramic routes as practiced in the lab is close to 99%. Conventionally prepared material is compared with material prepared using microwave heating in terms of structure, morphology, and optical properties, including quantum yield and thermal quenching of luminescence. Finally, the microwave-prepared compounds have been incorporated into light-emitting diode 'caps' to test their performance characteristics in a real device, in terms of their photon efficiency and color coordinates.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2012

Asymptotically-Equal-To 10 eV ionization shift in Ir K{alpha}{sub 2} from a near-coincident Lu K-edge

Close to an x-ray filter's K-edge the transmission depends strongly on the photon energy. For a few atom pairs, the K-edge of one is only a few tens of eV higher than a K-line energy of another, so that a small change in the line's energy becomes a measurable change in intensity behind such a matching filter. Lutetium's K-edge is Asymptotically-Equal-To 27 eV above iridium's K{alpha}{sub 2} line, Asymptotically-Equal-To 63.287 keV for cold Ir. A Lu filter reduces this line's intensity by Asymptotically-Equal-To 10 % when it is emitted by a plasma, indicating an ionization shift {Delta}E Asymptotically-Equal-To 10{+-}1 eV.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2012

Near-coincident K-line and K-edge energies as ionization diagnostics for some high atomic number plasmas

For some high atomic number atoms, the energy of the K-edge is tens of eVs higher than the K-line energy of another atom, so that a few eV increase in the line's energy results in a decreasing transmission of the x-ray through a filter of the matching material. The transmission of cold iridium's Asymptotically-Equal-To 63.287 keV K{alpha}{sub 2} line through a lutetium filter is 7% lower when emitted by ionized iridium, consistent with an energy increase of {Delta}{epsilon} Asymptotically-Equal-To 10{+-}1 eV associated with the ionization. Likewise, the transmission of the K{beta}{sub 1} line of ytterbium through a near-coincident K-edge filter changes depending on plasma parameters that should affect the ionization. Systematic exploration of filter-line pairs like these could become a unique tool for diagnostics of suitable high energy density plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗