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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Universal phase dynamics in VO 2 switches revealed by ultrafast operando diffraction

Understanding the pathways and time scales underlying electrically driven insulator-metal transitions is crucial for uncovering the fundamental limits of device operation. Using stroboscopic electron diffraction, we perform synchronized time-resolved measurements of atomic motions and electronic transport in operating vanadium dioxide (VO 2 ) switches. We discover an electrically triggered, isostructural state that forms transiently on microsecond time scales, which is shown by phase-field simulations to be stabilized by local heterogeneities and interfacial interactions between the equilibrium phases. This metastable phase is similar to that formed under photoexcitation within picoseconds, suggesting a universal transformation pathway. Our results establish electrical excitation as a route for uncovering nonequilibrium and metastable phases in correlated materials, opening avenues for engineering dynamical behavior in nanoelectronics.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Investigation into Texture and Structure of MA2-1PCh Magnesium Alloy after Equal Channel Angular Extrusion and Annealing by Quantitative X-Ray Texture Analysis and Electron Backscatter Diffraction

This article discusses application of quantitative X-ray texture analysis (QTXA) based on measurement of direct pole figures and electron backscatter diffraction (EBSD) aimed at study of peculiarities of formation of texture and structure of MA2-1pch magnesium alloy after equal channel angular extrusion (ECAE) and subsequent annealing. Shear bands with the width of 60 μm oriented at 45°–50° to the extrusion direction are revealed, where an inclined scattered basis texture is detected, and outside of these bands, a prismatic texture. As a consequence, basic sliding is activated in the shear bands, which is confirmed by the distribution of Schmid factors. The influence of texture and orientation of shear bands on anisotropy of strength mechanical properties of alloy is discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis, X-ray Diffraction Characterization, Mössbauer Spectroscopy, and Dielectric Properties of Solid Solutions in the PbFe{sub 2/3}W{sub 1/3}O{sub 3}–PbSc{sub 2/3}W{sub 1/3}O{sub 3} System

Ceramic Pb(Fe{sub 1–x}Sc{sub x}){sub 2/3}W{sub 1/3}O{sub 3} samples with 0 ≤ x ≤ 1 have been prepared and characterized by X-ray diffraction, Mössbauer spectroscopy, and dielectric and pyroelectric measurements. The stoichiometry ranges of the perovskite solid solutions in this system have been identified, their structural parameters have been determined, and their dielectric permittivity, dielectric loss tangent, resistivity, and thermally stimulated depolarization current have been measured as functions of temperature. The composition dependences of the dielectric properties for the solid solutions have been obtained. The solid solutions have been shown to exhibit ferroelectric relaxor properties, with a well-defined maximum in their permittivity in the range 180–250 K.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Spectral and Angular Dependences of the Efficiency of Three-Layer Relief-Phase Diffraction Elements of the IR Range

Within the framework of the scalar and rigorous diffraction theory based on solving a system of Maxwell equations, saw-tooth relief-phase three-layer microstructures designed for the work with polychromatic radiation of the mid-IR range (3 ≤ λ ≤ 5 μm) are studied. The series of effective microstructures composed of different optical materials is extended, and the depths of their reliefs are minimized. The series is extended, in particular, owing to microstructures in which Fresnel losses for reflection from both reliefs do not exceed 10%. This factor, in combination with the relatively low total relief depth, can turn out to be decisive when choosing one or another microstructure for solving a specific scientific or technological problem.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

On Diffraction Phenomena in Sensors of Surface Waves

The diffraction phenomena associated with the limited aperture size of an incident wave are considered on the basis of a theoretical method for studying the reflection of a plane electromagnetic wave from a plane-layered multifilm structure with homogeneous films. The proposed theory is applied to the analysis of the sensitivity of sensors based on surface waves.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Neutron diffraction study of the formation kinetics of ordered antiphase domains in titanium carbohydride TiC{sub x}H{sub y}

The kinetics of formation and growth of ordered antiphase domains (APDs) in titanium carbohydride TiC{sub 0.50}H{sub 0.21} has been investigated by neutron diffraction. A model of ordered APDs is proposed. It is established that the pronounced ordering of interstitial atoms and APDs begin at 450°C. It is shown that the period of ordered APDs (P ≈ 10–12) is independent of the exposure time at a constant temperature. It is found that the temperature of ordered APDs, T{sub OAPD}, increases nonlinearly with an increase in the carbon concentration in the range 0.50 ≤ C/Ti ≤ 0.70. The formation temperature of ordered APDs is found to correlate with the concentration dependence of the order–disorder transition temperature and be 0.60 of the order–disorder transition temperature: T{sub APD} = 0.60Τ{sub C}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Synthesis and X-ray diffraction study of Cu{sub 2}ZnSn(S{sub x}Se{sub 1-x}){sub 4} solid solutions

Quaternary compounds Cu{sub 2}ZnSnS{sub 4} and Cu{sub 2}ZnSnSe{sub 4} and solid solutions on their basis have been fabricated by one-temperature synthesis from elementary components: Cu, Zn, Sn, S, and Se. Single crystals of these compounds have been grown by the method of chemical gas-transport reactions from polycrystalline samples. The compositional dependence of the unit-cell parameters of Cu{sub 2}ZnSn(S{sub x}Se{sub 1–x}){sub 4} has been investigated by X-ray diffraction. It is found that parameters a and c linearly decrease with an increase in sulfur concentration in accordance with Vegard’s law. The temperature dependences of parameters a and thermalexpansion coefficients α{sub a} of Cu{sub 2}ZnSnS{sub 4} and Cu{sub 2}ZnSnSe{sub 4} single crystals in the range of 100–300 K are determined.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

X-ray diffraction analysis of LiCu{sub 2}O{sub 2} crystals with additives of silver atoms

Silver-containing LiCu{sub 2}O{sub 2} crystals up to 4 × 8 × 8 mm in size were grown by the crystallization of 80(1-x)CuO · 20{sub x}AgNO{sub 3} · 20Li{sub 2}CO{sub 3} (0 ≤ x ≤ 0.5) mixture melt. According to the X-ray spectral and Rietveld X-ray diffraction data, the maximum amount of silver incorporated in the LiCu{sub 2}O{sub 2} structure is about 4 at % relative to the copper content. It was established that silver atoms occupy statistically crystallographic positions of lithium atoms. The incorporation of silver atoms is accompanied by a noticeable increase in parameter c of the LiCu{sub 2}O{sub 2} rhombic unit cell, a slight increase in parameter a, and a slight decrease in parameter b.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Crystallization and preliminary X-ray diffraction study of phosphopantetheine adenylyltransferase from M. tuberculosis crystallizing in space group P3{sub 2}

Crystals of M. tuberculosis phosphopantetheine adenylyltransferase were grown in microgravity by the capillary counter-diffusion method through a gel layer. The X-ray diffraction data set suitable for the determination of the three-dimensional structure at atomic resolution was collected from one crystal at the Spring-8 synchrotron facility to 2.00-Å resolution. The crystals belong to sp. gr. P3{sub 2} and have the following unit-cell parameters: a = b = 106.47 Å, c = 71.32 Å, α = γ = 90°, β = 120°. The structure was solved by the molecular-replacement method. There are six subunits of the enzyme comprising a hexamer per asymmetric unit. The hexamer is a biologically active form of phosphopantetheine adenylyltransferase from M. tuberculosis.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Dimorphism of RF{sub 3} (R = La–Nd) crystals based on the data of X-ray diffraction studies

The ratio of two forms of tysonite in nominally pure single crystals of RF{sub 3} (R = La–Nd) obtained from melts under identical conditions (the as-grown state) is studied for the first time by X-ray diffraction. Crystals of RF{sub 3} with R = La–Nd belong to the β-LaF{sub 3} structural type (space group P3̄c1, Z = 6) and form twins. Samples 0.2–0.4 in diameter contain inclusions of the high-temperature a form (space group P6{sub 3}/mmc, Z = 2). It is shown that twinning and dimorphism of the RF{sub 3} crystals (R = La–Nd) have a common structural basis.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

X-ray diffraction study of Ba{sub 3}TaFe{sub 3}Si{sub 2}O{sub 14} single crystal—a promising langasite-type multiferroic

Ba{sub 3}TaFe{sub 3}Si{sub 2}O{sub 14} single crystals (sp. gr. P321, Z = 1), promising langasite-type multiferroics, have been grown by floating zone melting. An accurate X-ray diffraction study of Ba{sub 3}TaFe{sub 3}Si{sub 2}O{sub 14} single crystal has been performed using two datasets, obtained independently for two different orientations of the same sample on a diffractometer equipped with a CCD area detector at 295 K. Structure refinement is performed based on an averaged dataset: a = 8.5355(1) Å, c = 5.2332(1) Å, sp. gr. P321, Z = 1; the R factors of model structure refinement were found to be R/wR = 1.02/1.23% for 4552 independent reflections. Disordering asymmetry is revealed for the magnetic Fe ion in the 3f site and the Ba cation in the 3e site.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Synthesis and X-ray diffraction study of new uranyl malonate and oxalate complexes with carbamide

Two new malonate-containing uranyl complexes with carbamide of the formulas [UO{sub 2}(C{sub 3}H{sub 2}O{sub 4})(Urea){sub 2}] (I) and [UO{sub 2}(C{sub 3}H{sub 2}O{sub 4})(Urea){sub 3}] (II), where Urea is carbamide, and one uranyl oxalate complex of the formula [UO{sub 2}(C{sub 2}O{sub 4})(Urea){sub 3}] (III) were synthesized, and their crystals were studied by X-ray diffraction. The main structural units in crystals I are the electroneutral chains [UO{sub 2}(C{sub 3}H{sub 2}O{sub 4})(Urea){sub 2}]{sub ∞} belonging to the crystal-chemical group AT{sup 11}M{sub 2}{sup 1} (A = UO{sub 2}{sup 2+}, T{sup 11} = C{sub 3}H{sub 2}O{sub 4}{sup 2-}, M{sup 1} = Urea) of uranyl complexes. Crystals II and III are composed of the molecular complexes [UO{sub 2}(L)(Urea){sub 3}], where L = C{sub 3}H{sub 2}O{sub 4}{sup 2-} or C{sub 2}O{sub 4}{sup 2-}, belonging to the crystal-chemical group AB{sup 01}M{sub 3}{sup 1} (A = UO{sub 2}{sup 2+}, B{sup 01} = C{sub 3}H{sub 2}O{sub 4}{sup 2-} or C{sub 2}O{sub 4}{sup 2-}, M{sup 1} = Urea). The characteristic features of the packing of the uranium-containing complexes are discussed in terms of molecular Voronoi–Dirichlet polyhedra. The effect of the Urea: U ratio on the structure of uranium-containing structural units is considered.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Calibration of CryojetHT and Cobra Plus Cryosystems used in X-ray diffraction studies

CryoJetHT (Oxford Instruments) and Cobra Plus (Oxford Cryosystems) cryosystems, which are used for sample cooling in X-ray diffraction experiments, have been calibrated. It is shown that the real temperature in the vicinity of the sample differs significantly (the deviation is as high as 8–10 K at low temperatures) from the temperature recorded by authorized sensors of these systems. The calibration results are confirmed by measurements of the unit-cell parameters of GdFe{sub 3}(BO{sub 3}){sub 4} single crystal in the temperature range of its phase transition. It is shown that, to determine the real temperature of a sample, one must perform an independent calibration of cryosystems rather than rely on their ratings.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

X-ray diffraction studies of the Tl(GaS{sub 2}){sub 1–x}(InSe{sub 2}){sub x} solid solutions

The unit-cell parameters of crystals obtained in the Tl(GaS{sub 2}){sub 1–x}(InSe{sub 2}){sub x} system are measured by X-ray diffraction. The relationship between these parameters and composition is determined. It is shown that, with growing x, the a, b, and c parameters increase and the β angle decreases. Two types of solid solutions are found in the Tl(GaS{sub 2}){sub 1–x}(InSe{sub 2}){sub x} system: one is based on compound TlGaS{sub 2} with monoclinic structure and the other is based on TlInSe{sub 2} with tetragonal structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Time and space domain separation of pulsed X-ray beams diffracted from vibrating crystals

It is known that a set of additional reflections (satellites) may arise on rocking curves in the case of X-ray diffraction in the Bragg geometry from crystals where high-frequency ultrasonic vibrations are excited. It is shown that, under certain conditions, the pulse wave fields of the satellites and main reflection may be intersected in space (playing the role of pump and probe beams) and in time (forming interference superlattices).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Accurate X-ray diffraction studies of KTiOPO{sub 4} single crystals doped with niobium

Single crystals of potassium titanyl phosphate doped with 4% of niobium (КТР:4%Nb) and 6% of niobium (KTP:6%Nb) are studied by accurate X-ray diffraction at room temperature. The niobium atoms are localized near the Ti1 and Ti2 atomic positions, and their positions are for the first time refined independent of the titanium atomic positions. Maps of difference electron density in the vicinity of K1 and K2 atomic positions are analyzed. It is found that in the structure of crystal КТР:4%Nb, additional positions of K atoms are located farther from the main positions and from each other than in КТРand KTP:6%Nb crystals. The nonuniform distribution of electron density found in the channels of the КТР:4%Nb structure is responsible for ~20% increase in the signal of second harmonic generation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

X-ray mapping in heterocyclic design: 18. X-ray diffraction study of a series of derivatives of 3-cyanopyridine-2-one with annelated heptane and octane cycles

Seven new, previously unknown, bicyclic and tricyclic heterocycles based on derivatives of 3-cyanopyrid-2-ones are obtained: 2-oxo-2,5,6,7,8,9-hexahydro-1H-cyclohepta[b]pyridine-3-carbonitrile, C{sub 11}H{sub 12}N{sub 2}O (1a); 2-[2-(4-chlorophenyl)-2-oxoethoxy]-6,7,8,9-tetrahydro-5H-cyclohepta[b] pyridine-3-carbonitrile, C{sub 19}H{sub 17}ClN{sub 2}O{sub 2} (2a); (3-amino-6,7,8,9-tetrahydro-5H-cyclohepta[b]furo[3,2-e]pyridin-2-yl)(4- chlorophenyl)methanone, C{sub 19}H{sub 17}ClN{sub 2}O{sub 2} (3); 2-oxo-1,2,5,6,7,8,9,10-octahydrocycloocta[b]pyridine-3-carboxamide, C{sub 12}H{sub 16}N{sub 2}O{sub 2} (4); 2-[2-(4-chorophenyl)-2-oxoethoxy]-5,6,7,8,9,10 -hexahydrocycloocta[b]pyridine-3-carboxamide, C{sub 20}H{sub 21}ClN{sub 2}O{sub 3} (5a); 1-[2-(4-chlorophenyl)-2-oxoethyl]-2-oxo-1,2,5,6,7,8,9,10 -octahydrocycloocta[b]pyridine-3-carboxamide, C{sub 20}H{sub 21}ClN{sub 2}O{sub 3} (5b); and 2-[2-(4-chlorophenyl)-2-oxoethoxy]-5,6,7,8,9,10-hexahydrocycloocta[b] pyridine-3-carbonitrile, C{sub 20}H{sub 19}ClN{sub 2}O{sub 2}, (6). All compounds are characterized by {sup 1}H NMR spectroscopy, and their crystal structures are determined by X-ray diffraction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗