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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Defect Structure in Quantum-Cutting Yb3+-Doped CsPbCl3 Perovskites Probed by X-Ray Absorption and Atomic Pair Distribution Function Analysis

Ytterbium-doping in all-inorganic lead-halide perovskites (CsPb(Cl1-xBrx)3) generates novel properties including quantum cutting and narrow line emission, making these materials attractive spectral down-converters for solar photovoltaics. The relationship between this optical efficiency and the defect structure(s) associated with Yb3+ dopants within perovskites is not well understood. Various charge-neutral doping motifs have previously been proposed and studied computationally, including clusters involving two substitutional Yb3+ ions charge-compensated by a single local Pb2+ vacancy. Near-band-edge defect states associated with such motifs are believed to play an important mechanistic role in quantum cutting itself. Here, we report the results of X-ray absorption and X-ray total-scattering measurements on ytterbium-doped CsPbCl3. XANES shows that the dopant oxidation state is exclusively Yb3+, and a combination of Yb L3 and Pb L3 EXAFS shows that this Yb3+ substitutes exclusively at Pb2+ sites, where it adopts a pseudo-octahedral [YbCl6]3- coordination environment. Shell-by-shell fits to the data show a short Yb-Cl bond distance of 2.58 Å compared to the Pb-Cl bond distance of 2.83 Å. We confirm this finding by X-ray pair distribution function analysis, which also shows evidence of additional Pb2+ vacancy formation induced by Yb3+ doping. We evaluate whether this is the primary mechanism of charge compensation using simulated EXAFS and pair distribution function data for several computed defect structures. Together, these results resolve the local dopant structures and charge-compensation mechanisms in lanthanide-doped all-inorganic lead-halide perovskites, and, as such, significantly advance the understanding of structure-function relationships in this important class of materials.

Kluherz, Kyle (ORCID:0000000279865167)↗
DOE OSTI2023

Phase stability and tensorial thermal expansion properties of single to high-entropy rare-earth disilicates

Temperature limitations in nickel-base superalloys have resulted in the emergence of SiC-based ceramic matrix composites as a viable replacement for gas turbine components in aviation applications. Higher operating temperatures allow for reduced fuel consumption but present a materials design challenge related to environmental degradation. Rare-earth disilicates (RE 2 Si 2 O 7 ) have been identified as coatings that can function as environmental barriers and minimize hot component degradation. In this work, single- and multiple-component rare-earth disilicate powders were synthesized via a sol-gel method with compositions selected to exist in the monoclinic C 2/m phase (β phase). Phase stability in multiple cation compositions was shown to follow a rule of mixtures and the C 2/m phase could be realized for compositions that contained up to 25% dysprosium, which typically only exists in a triclinic, P $\bar1$, phase. All compositions exhibited phase stability from room temperature to 1200°C as assessed by X-ray diffraction. The thermal expansion tensors for each composition were determined from high-temperature synchrotron X-ray diffraction and accompanying Rietveld refinements. It was observed that ytterbium-containing compositions had larger changes in the α 31 shear component with increasing temperature that led to a rotation of the principal axes. Principal axes rotation of up to 47° were observed for ytterbium disilicate. The results suggest that microstructure design and crystallographic texture may be essential future avenues of investigation to ensure thermo-mechanical robustness of rare-earth disilicate environmental barrier coatings.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Optomechanical interaction in fibre lasers with micro-optomechanical resonance structures

We report the results of studies of fibre lasers with passive modulators based on light-excited micro-optomechanical resonance structures (micro-oscillators). It is shown that in fibre lasers based on active fibres doped with rare-earth elements (Er, Er/Yb, Yb, Nd), the optomechanical interaction of laser radiation with micro-oscillators of various types (fibre-optic, microvolume) leads to self-oscillations of the characteristics of laser radiation at frequencies of relaxation oscillations and intermode beats synchronised with the frequencies of elastic eigenoscillations of micro-oscillators. It is found that in an ultra-long erbium – ytterbium fibre laser with a nonlinear mirror based on a microcantilever, laser photothermal excitation of the second mode of elastic transverse oscillations of the microcantilever makes it possible to perform passive mode locking exclusively due to Q-switching of the laser cavity. Pulsed lasing with a controlled repetition rate (∼76 kHz), a pulse duration of 2 – 5 μs and an output energy of 0.1 μJ per pulse is implemented. Based on a simplified physical model of the indicated fibre lasers with micro-oscillators, we have developed an approximate mathematical model describing the regimes of passive mode locking of fibre lasers with micro-oscillators that play the role of mirrors with a nonlinear reflection coefficient in the laser cavity. The prospects for the development and application of the considered laser systems are discussed. (control of laser radiation parameters)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Lasing dynamics of diode-pumped Yb – Er laser with a passive Q switch exposed to high-power external light

The temporal dynamics of diode-side-pumped Yb – Er laser, with a passive Co{sup 2+} : MgAl{sub 2}O{sub 4} Q switch illuminated by a light beam (total fluence of 0.15 – 0.16 J cm{sup −2}) from a semiconductor pulsed module, is investigated. It is shown that, using this external illumination, one can change the lasing onset delay and the time jitter ΔT{sub gi}. The dependence of ΔT{sub gi} on the interval between the instant of switching the illumination module on and the lasing peak position t{sub i} has a minimum at |t{sub i}| ≈ 10 μs. The decrease in ΔT{sub gi} with a change in |t{sub i}| from 90 to 10 μs indicates that instant of lasing peak occurrence for the Yb – Er laser is partially controlled by the pulse from the highly stable semiconductor module. If |t{sub i}| < 10 μs, the enhanced luminescence fluence in the cavity of Yb – Er laser exceeds 0.16 J cm{sup −2}; the light beam from the module does not affect much the lasing process in the ytterbium – erbium laser; and, as a consequence, the time jitter recovers the initial value. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Decreasing the amplitude of macroscopic quantum fluctuations in the case of transient SRS

It is shown experimentally that, under the conditions of transient stimulated Raman scattering, pumping by two successive orthogonally polarised laser pulses makes it possible to reduce the amplitude of macroscopic quantum energy fluctuations of a Stokes pulse by a factor of 4 in comparison with single-shot pumping. An energy dispersion of 0.9 % for the first Stokes component is obtained in hydrogen at a relative energy dispersion of ytterbium laser pulses of 0.4 %. (nonlinear optical phenomena)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

The APOGEE Data Release 16 Spectral Line List

The updated H-band spectral-line list (from λ15000–17000) adopted by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) for the SDSS-IV Data Release 16 (DR16) is presented in this work. The APOGEE line list is a combination of atomic and molecular lines, with data drawn from laboratory, theoretical, and astrophysical sources. Oscillator strengths and damping constants are adjusted using high signal-to-noise, high-resolution spectra of the Sun, and α Boo (Arcturus), as “standard stars.” Updates to the DR16 line list, as compared to the previous DR14 version, include the addition of molecular H{sub 2}O and FeH lines, as well as a much larger (by a factor of ∼4) atomic line list, including a significantly greater number of transitions with hyperfine splitting. More recent references and line lists for the crucial molecules, CO and OH, as well as for C{sub 2} and SiH, are also included. In contrast to DR14, DR16 contains measurable lines from the heavy neutron-capture elements cerium (as Ce ii), neodymium (as Nd ii), and ytterbium (as Yb ii), as well as one line from rubidium (as Rb i), which may be detectable in a small fraction of APOGEE red giants.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Removal of Metal Oxides from Reactor Metals/Alloys by Laser Ablation

Storage of low and intermediate level radioactive waste in a deep geological repository (L and ILW DGR): - Large volumes of metallic waste = increased production of hydrogen gas. - Large fraction of the metallic wastes are out-of-core reactor components. - Carbon steel feeder pipes. - Radioactive contamination is concentrated within the surface oxides. - Removal of surface contaminants would lead to volume reduction of metallic waste that is stored in L and ILW DGR. - Current decontamination techniques generate large volumes of secondary waste. Objectives: Oxide removal from carbon steel using a ytterbium fiber laser (1064 nm) with a particular focus on identifying the key laser parameters that affect the removal efficiency. Advantages of laser ablation: Generate low volumes of waste, Flexibility of deployment, Remote operation. Grow an oxide film on carbon steel with the incorporation of cobalt. Optimize laser cleaning technology for the removal of surface oxides. Incorporate an oxide collection system for the ablated particles. Conclusions: Objective 1 - Simulated inactive oxides on carbon steel, using Co{sup 2+} as a surrogate for Co radionuclide. Objective 2 - Optimized laser parameters (200 MW/cm{sup 2}, 3 scans, 15 μm overlap); Complete removal of cobalt from surface and bulk metal with optimized cleaning settings. Objective 3 - Glass fiber media H14 HEPA filters had highest collection yield; High oxide collection yields (∼100%). Future Work: Further testing of the liquid trap will verify the efficacy of the HEPA filter and determine the amount of ablated oxides that pass through. Testing of the laser ablation system needs to be done on other reactor materials along with the incorporation of different transition metal cations. Improvements to the oxide collection system are required to improve collection yields.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Ammonothermal Synthesis, Crystal Structure, and Vibrational Properties of the Doubly Deprotonated Calcium Guanidinate, CaC(NH) 3

We report the synthesis of the doubly deprotonated calcium guanidinate, CaC(NH) 3 , from liquid ammonia and its crystal structure as determined from powder X‐ray and neutron diffraction, and confirmed using CNH elemental analysis and infrared (IR) spectroscopy data. CaC(NH) 3 crystallizes in the hexagonal system with space group P 6 3 / m (no. 176) with Z = 2 and a = 5.2666(13) Å, c = 6.5881(6) Å and V = 158.25(4) Å 3 . We also compare the structural similarities and differences of this phase with the isotypical strontium and ytterbium compounds.

Ogutu, George↗
DOE OSTI2026

Diethylenetriamine-functionalized graphene oxide: Insights into ion adsorption and applications in rare earth element separation

The growing demand for critical minerals and materials requires atom- and energy-efficient, selective separations to overcome the challenges posed by the similar chemical and physical properties of the rare earth elements (REEs) and their low concentrations in unconventional domestic feedstocks. Here, in this study, we developed diethylenetriamine-functionalized graphene oxide (DETA-GO) as a membrane material for REE adsorption and separation. Synthesis conditions were optimized to maximize nitrogen incorporation while also preserving GO dispersibility for facile membrane fabrication. We investigated the mechanism of amine functionalization, the nitrogen-bonding configurations, the organization of the interlayer transport channels, and the resulting effects on ion and water transport for REE separations. Neat-GO and DETA-GO multilayer laminate membranes were fabricated by vacuum filtration onto polymer supports. To investigate the effects of amine functionalization, the membranes were characterized using scanning electron microscopy, Raman, Fourier transform infrared, and X-ray photoelectron spectroscopy, as well as grazing-incidence X-ray diffraction measurements. Ion permeation experiments with representative lanthanum (La 3+ ) and ytterbium (Yb 3+ ) solutions revealed enhanced ion adsorption and water transport through DETA-GO membranes compared to neat-GO. The strong affinity of the membranes for multivalent REEs was also validated with conductivity and inductively coupled plasma mass spectrometry measurements. Atomistic insight into the role of amine functionalization in modulating nanochannel architecture and long-term stability, optimizing adsorption sites, and regulating REE and water transport was obtained using classical molecular dynamics simulations. Collectively, our joint experimental and theoretical study demonstrates the potential of DETA-GO membranes for selective REE separations, offering insights into ion-binding mechanisms, water-transport properties, and nanochannel optimization for the recovery of critical materials from aqueous feedstocks.

Adsorbent↗
DOE OSTI2023

Low-cost thermal/environmental barrier coatings: A first-principles study

Development of low-cost advanced thermal/environmental barrier coating (T/EBC) materials with acceptable thermal and mechanical properties is essential for safeguarding ceramic composites substrate against thermal and chemical degradation, thereby enhancing the efficiency of components in the high-temperature section of gas turbine engines. To this end, here we employed density functional theory-based approaches to predict the thermodynamic, mechanical, and thermal properties of rare earth disilicates based on abundant rare earth elements, namely La 2 Si 2 O 7 and Ce 2 Si 2 O 7 , as potential alternatives to the current-state-of-the-art ytterbium disilicate EBCs that uses expensive and scarce element Yb. The present study predicts that G-phase Ce 2 Si 2 O 7 has an ultralow thermal conductivity (0.26 W/m/K at 1500 K) and the apparent bulk coefficient of thermal expansion (ABCTE) (≈6.9x10 -6 K -1 ) slightly higher than SiC, demonstrating great potential as low-cost high-performance T/EBC. However, La 2 Si 2 O 7 and Ce 2 Si 2 O 7 undergo an A- to G-phase polymorphic transition at around 1470 K, resulting in significant changes to crystal structure and lattice parameters, and accordingly CTE and lattice thermal conductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Crystal growth of new high light yield halide perovskite scintillator RbSrI 3

X-ray radiography systems are a key national security technology enabling non-invasive cargo screening. However, the scintillators currently used in these systems have limitations in performance that prompt research for new suitable materials. Here, in this work, crystal growth, physical properties, and optical and scintillation properties of a new halide perovskite scintillator RbSrI 3 were investigated for the first time. The melting point was determined to be 453 °C. Divalent europium and ytterbium were investigated as potential luminescent activators. Light yield and energy resolution of RbSrI 3 :Eu 5 mol% was 78,700 ph/MeV and 2.8 % at 662 keV, and that of RbSrI 3 :Yb 0.5 mol% was 24,000 ph/MeV and 4.9 % at 662 keV.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Dry air cyclic oxidation of mixed Y/Yb disilicate environmental barrier coatings and bare silica formers

Here mixed Y and Yb disilicate coatings (Y/Yb)DS have been proposed as dual function thermal and environmental barrier coatings (EBCs) for protecting SiC-based ceramic matrix composites in gas-turbine environments. As an initial step, the 1350 °C dry air cyclic oxidation of atmospheric plasma sprayed (Y 1.2 /Yb 0.8 )DS and ytterbium disilicate/ytterbium monosilicate (YbDS/YbMS) EBCs deposited onto Si bond coatings was compared. As a baseline for evaluating EBC oxidant permeability, the dry air cyclic oxidation scale growth rates for bare silica formers (SiC, Si) were also measured and were consistently higher than rates previously measured after isothermal oxidation. Regarding Si bond coat oxidation rates underlying (Y/Yb)DS and YbDS/YbMS EBCs, the thinner silica scale formed under the thinner and denser (Y/Yb)DS coatings suggested a lower oxidant permeability than YbDS/YbMS. After 500 1-h cycles, the (Y/Yb)DS coating was comprised of only the β-polymorph disilicate and minor amounts of the X-2 phase monosilicate phase. Negligible differences in oxidation kinetics for (Y/Yb)DS coatings over the 90 – 240 µm thickness range were observed.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Radiative transition probabilities of neutral and singly ionized rare earth elements (La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) estimated by laser-induced breakdown spectroscopy

Rare earth elements (REEs) are essential to society given their prevalence in many modern technologies. Quantitative elemental analysis of REEs is therefore a critical capability. Calibration free–laser-induced breakdown spectroscopy (CF-LIBS) is a rapidly maturing and promising approach to quantitative elemental analysis with many attractive qualities. The application of CF-LIBS to analyzing samples containing the REEs is hindered by a lack of fundamental data, specifically transition probabilities (TPs). As such, this study seeks to help address this knowledge deficiency by reporting 967 previously unreported TPs for 13 REEs (lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). The method developed in this study to estimate the TPs requires small amounts of material (a few nanograms) compared with other approaches (~ milligrams), uses non-specialized equipment, and does not involve complicated sample preparations.

(LIBS)↗
DOE OSTI2021

Transport properties and thermal behavior of YbMnSb 2 semimetal above room temperature

Single crystals of ytterbium manganese diantimonide, YbMnSb 2 have been grown from a high-temperature reaction of the elements, employing molten Sb as self-flux. This phase crystallizes in the tetragonal centrosymmetric space group P4/nmm (No. 129) and adopts the ZrCuSiAs structure type. Here, the structure consists of Sb-based square nets and PbO-type layers formed by fused [MnSb 4/4 ] tetrahedra. YbMnSb 2 is stable under ambient atmosphere and incongruently melts at a temperature of ca. 1120 K. In the temperature range from 300 K to 450 K, the electrical resistivity of the as-grown single-crystalline material is as low as 3.2 mΩ cm, while its thermopower is as high as 180 μV/K. As such, YbMnSb 2 shows promise for thermoelectric applications in the mid-temperature region, with an estimated power factor of 0.85–0.95 mW/(m K 2 ).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

A theoretical study of the bonding properties of R 4 Sb 3 compounds

Here, this study investigates the electronic structure and bonding properties of rare-earth antimonide compounds, specifically Yb 4 Sb 3 and La 4 Sb 3 , utilizing density functional theory calculations. The analysis reveals that Yb 4 Sb 3 exhibits a predominantly ionic character whereas La 4 Sb 3 displays a greater degree of covalent bonding. Moreover, the presence of divalent ytterbium leads to p-type conduction at high temperatures in Yb 4 Sb 3 . Conversely, La 4 Sb 3 displays n-type conduction because of a larger electronic transfer from the rare-earth metal towards antimony. These findings provide valuable insights into the structural and electronic properties that govern the performance of R 4 Sb 3 compounds, contributing to the development of advanced materials for thermoelectric energy conversion.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Crystal Chemistry and Thermodynamics of HREE (Er, Yb) Mixing in a Xenotime Solid Solution

Rare earth elements (REEs), the 15 naturally occurring lanthanides plus yttrium and scandium, are ubiquitously used in modern life as they are critical components of many advanced devices and technologies. However, the demand for REEs is not equal, with the heavy rare earth elements (HREEs) having a higher demand. Xenotime (HREEPO 4 ) is an important HREE ore mineral and globally is an economical source of HREE. Most of the crystallographic and thermodynamic properties of xenotime endmembers have been elucidated by calorimetric, solubility, and high-pressure studies. Yet, in natural systems, endmembers are rarely encountered, and instead, REE solid solutions are more commonly observed. Here, we characterize the crystal chemistry, thermodynamics of HREE mixing, and high-temperature material behaviors and thermochemistry of a synthetic erbium (Er)-ytterbium (Yb) binary xenotime solid solution (Er (x) Yb (1-x) PO 4 ) using a suite of experimental techniques, including X-ray fluorescence spectroscopy, synchrotron X-ray powder diffraction implemented with Rietveld analysis, Fourier transform infrared spectroscopy coupled with attenuated total reflectance, Raman spectroscopy, thermogravimetric analysis coupled with differential scanning calorimetry, and high-temperature oxide melt drop solution calorimetry. Our results shed light on the formation of natural xenotimes and lay the foundation for their industrial applications as thermal coating materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Solid-state laser refrigeration of a composite semiconductor Yb:YLiF 4 optomechanical resonator

Photothermal heating represents a major constraint that limits the performance of many nanoscale optoelectronic and optomechanical devices including nanolasers, quantum optomechanical resonators, and integrated photonic circuits. Here, we demonstrate the direct laser refrigeration of a semiconductor optomechanical resonator >20 K below room temperature based on the emission of upconverted, anti-Stokes photoluminescence of trivalent ytterbium ions doped within a yttrium-lithium-fluoride (YLF) host crystal. Optically-refrigerating the lattice of a dielectric resonator has the potential to impact several fields including scanning probe microscopy, the sensing of weak forces, the measurement of atomic masses, and the development of radiation-balanced solid-state lasers. In addition, optically refrigerated resonators may be used in the future as a promising starting point to perform motional cooling for exploration of quantum effects at mesoscopic length scales, temperature control within integrated photonic devices, and solid-state laser refrigeration of quantum materials.

42 ENGINEERING↗
DOE OSTI2022

Towards understanding the magnetic properties of the breathing pyrochlore compound Ba3Yb2Zn5O11through single-crystal studies

Abstract Ba 3 Yb 2 Zn 5 O 11 is exceptional among breathing pyrochlore compounds for being in the nearly-decoupled limit where inter-tetrahedron interactions are weak, hosting isolated clusters or molecular magnet-like tetrahedra of magnetic ytterbium (Yb 3+ ) ions. In this work, we present the study carried out on single-crystal samples of the breathing pyrochlore Ba 3 Yb 2 Zn 5 O 11 , using a variety of magnetometry and neutron scattering techniques along with theoretical modeling. We employ inelastic neutron scattering to investigate the magnetic dynamics as a function of applied field (with respect to both magnitude and direction) down to a temperature of 70 mK, where inelastic scattering reveals dispersionless bands of excitations as found in earlier powder sample studies, in good agreement with a single-tetrahedron model. However, diffuse neutron scattering at zero field and dc-susceptibility at finite field exhibit features suggesting the presence of excitations at low-energy that are not captured by the single tetrahedron model. Analysis of the local structure down to 2 K via pair distribution function analysis finds no evidence of structural disorder. We conclude that effects beyond the single tetrahedron model are important in describing the low-energy, low-temperature physics of Ba 3 Yb 2 Zn 5 O 11 , but their nature remains undetermined.

36 MATERIALS SCIENCE↗