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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

NIR luminescence studies on Er{sup 3+}:Yb{sup 3+} co-doped sodium telluroborate glasses for lasers and optical amplifer applications

Er{sup 3+}:Yb{sup 3+} co-doped Sodium telluroborate glasses were prepared with the chemical composition (49.5–x)B{sub 2}O{sub 3}+25TeO{sub 2}+5Li{sub 2}CO{sub 3}+10ZnO+10NaF+0.5Er{sub 2}O{sub 3}+xYb{sub 2}O{sub 3} (where x= 0.1, 0.5, 1.0 and 2.0 in mol %) following the melt quenching technique. With the addition of Yb{sup 3+} ions into Er{sup 3+} ions in the prepared glasses, the absorption cross-section values were found to increase due to the effective energy transfer from {sup 2}F{sub 5/2} level of Yb{sup 3+} ions to the {sup 4}I{sub 11/2} level of Er{sup 3+} ions. The fluorescence around 1550 nm correspond to the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition was observed under 980 nm pumping. Among the present glasses, integrated intensity was found to be higher for 1.0 mol% Yb{sup 3+} ion glass. The parameters such as stimulated emission cross- section, Gain bandwidth and quantum efficiency of the {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} transition was found to be higher for the NTBE1.0Y glass and the same is suggested for potential NIR lasers and optical amplifier applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

DSC and Raman studies of silver borotellurite glasses

Silver borotellurite glasses of composition: xAg{sub 2}O-yB{sub 2}O{sub 3}-(100-x-y)TeO{sub 2} (x=20-mol%, y = 0, 10, 20 and 30-mol%) were prepared and characterized by density, X-ray diffraction (XRD), differential scanning calorimetry, and Raman spectroscopy. XRD confirmed the amorphous structure of all samples. Density of glasses decreases while the glass transition temperature increases with increase in B{sub 2}O{sub 3} content from 10 to 30-mol%. Raman study shows that coordination number of Te with oxygen decreases steadily from 3.42 to 3.18 on adding B{sub 2}O{sub 3} due to the transformation of TeO{sub 4} into TeO{sub 3} units.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Thermal and structural properties of zinc modified tellurite based glasses

Glass system 60 TeO{sub 2} – 10 B{sub 2}O{sub 3}-(30-x) Bi{sub 2}O{sub 3}-x ZnO with mole fraction x = 10, 15, 20, 25 and 30 were synthesized by conventional melt quenching technique under controlled atmospheric conditions. The glass transition temperature (T{sub g}) has been determined using differential scanning Calorimetry (DSC) and its value is observed to increase with increase in ZnO content. This increase may be due to the increase in the concentration of the bridging oxygen (BO) atoms. IR and Raman spectra of the present glass system indicate that ZnO acts as network modifier and exists in ZnO{sub 4} units. TeO{sub 2} exists as TeO{sub 3}, TeO{sub 4}, and TeO{sub 3+1} structural units. Bismuth plays the role of network modifier with BiO{sub 6} octahedral structural units whereas B{sub 2}O{sub 3} exists in the form of BO{sub 3} trigonal and BO{sub 4} tetrahedral structural units.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Spectroscopic and energy transfer studies of Er{sup 3+} ions in B{sub 2}O{sub 3}–TeO{sub 2}–MgO–ZnO glasses

Composition dependent spectroscopic behavior of Er{sup 3+} doped telluroborate glasses were prepared and the energy transfer mechanism in Er{sup 3+} ions were investigated for 1.532 µm amplification. The emission cross-section and gain coefficient for {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} level of Er{sup 3+} ions have been analysed through the Judd-Ofelt and McCumber theory. The excited state decay curves were measured and the effect of TeO{sub 2} on the lifetime for {sup 4}I{sub 13/2}→{sup 4}I{sub 15/2} level of Er{sup 3+} ions has been associated with the various energy transfer mechanism. Further the interaction between Er{sup 3+} and OH{sup −} were investigated and it was confirmed that the OH free radicals in the prepared glasses are dominant quenching center through the non-radiative relaxation that causes the quenching of 1.532 µm amplification. The non-radiative rate through the OH content were calculated and compared with the reported Er{sup 3+} doped glasses.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Deep-UV generation in an SBO crystal with an irregular domain structure

Random (stochastic) quasi-phase matching is demonstrated for broadband radiation in a one-dimensional irregular strontium tetraborate nonlinear photonic crystal. Harmonic generation tunable in the range 187.5 - 215 nm is achieved. The average power of the generated signal is a quadratic function of pump power and reaches 1 {mu}W. In a steady-state model, taking into account sum frequency generation within the spectrum of the input light causes no broadening of the peaks in the spectrum of the generated signal. (nonlinear optical phenomena)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

High-peak power, passively Q-switched, composite, all-polycrystalline ceramic Nd:YAG/Cr{sup 4+}:YAG lasers

High-peak power, passively Q-switched, composite Nd : YAG/Cr{sup 4+} : YAG lasers consisting of all-polycrystalline bonded Nd:YAG and Cr{sup 4+}:YAG ceramics are developed, and two applications of such lasers are discussed. A 1.1-at. %-doped Nd:YAG/Cr{sup 4+}:YAG ceramic laser is fabricated, which is quasi-cw pumped by a diode laser in the Hz-range, delivering laser pulses of 2.5-mJ energy and 1.9-MW peak power. By frequency doubling the laser output in a LiB{sub 3}O{sub 5} (LBO) nonlinear crystal at room temperature, 0.36-mJ, 0.3-MW green laser pulses with 27 % conversion efficiency are produced at 532 nm. Furthermore, a highly doped (1.5-at. %) Nd:YAG/Cr{sup 4+}:YAG ceramic laser operates successfully in the range of pulse repetition rates from 50 to 500 Hz, yielding 0.8-to-1.0 mJ pulses with a peak power around 1 MW. The laser output beam is amplified in a master-oscillator - power-amplifier (MOPA) system to generate laser pulses with 11-mJ energy at a 250-Hz repetition rate. (lasers)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Generation of high-power femtosecond supercontinua in the near-IR spectral range using broadband parametric frequency conversion in LBO and DCDA crystals pumped at λ = 620 nm

The pump wavelength of parametric amplifiers based on CLBO, DCDA and LBO crystals and pumped by the second harmonic of a femtosecond Cr : forsterite laser (620 nm) is close to optimal for broadband amplification because of the proximity of group velocities of interacting pulses. Injection of a broadband continuum into the range of the signal-wave gain in LBO and DCDA parametric amplifiers, pumped at λ = 620 nm, leads to generation of broadband femtosecond pulses with a spectrum ranging from 1050 to 1600 nm and peak powers up to 20 MW. (nonlinear optical phenomena)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Investigation of Cu Species in Dealuminated Beta Zeolite Studied by Operando Closed-Cell Gas Reaction STEM

Direct conversion of ethanol to C3+ olefins is an attractive pathway to produce sustainable aviation fuels [1]. We recently reported a copper-containing catalyst supported on dealuminated (DeAl) beta zeolite that is capable of catalyzing cascade ethanol to olefins reactions with high olefins selectivity (88% C3+ olefin selectivity at 100% ethanol conversion). However, one of the deactivation mechanisms of the catalyst is copper sintering [2]. It was found that copper agglomerates can be redispersed through a simple oxidative treatment. To better understand the kinetics and process conditions conducive to redispersion, we studied the atmosphere and temperature dependent Cu species in Cu/DeAl-Beta catalyst under conditions matching those of the working catalyst.

beta zeolite↗
DOE OSTI2011

Multispace quantum interference in a {sup 57}Fe synchrotron Moessbauer source

A physical picture for coherent emission of {gamma} rays by a nuclear array excited with synchrotron radiation is given. The particular case of a pure nuclear Bragg reflection from the {sup 57}FeBO{sub 3} crystal is analyzed. During free de-excitation of the nuclei, a nuclear exciton polariton is developing inside the crystal and generates at the exit of the crystal a coherent {gamma}-ray beam. In the crystal the nuclear levels of {sup 57}Fe are split because of a combined magnetic and electric interaction. The rich picture of {gamma}-ray interference is described, which involves geometrical space, energy, and spin domains. In the vicinity of the Neel temperature of the crystal the magnetic splitting of nuclear levels nearly collapses. These conditions lead to drastic changes in the angular, energy, and temporal properties of the emitted radiation. The emission angular function, which in the approximation of a plane incident wave represents the emission intensity for different angular settings of the crystal near Bragg angle, strongly broadens and transforms to a double-hump structure with a central dip between the peaks. The energy and temporal distributions of the emitted radiation crucially depend upon the crystal angular setting. Beyond the central dip, the energy distribution of nuclear scattering acquires a complicated form with several satellites at various energies. In contrast, at the exact angular position of the central dip, the energy spectrum exhibits a single line shape with the line width close to the natural width of the nuclear resonance. The obtained results constitute the theoretical basis for the understanding and for the further elaboration of the {sup 57}Fe synchrotron Moessbauer source--the device that provides a collimated beam of intense and polarized {gamma} radiation in an energy bandwidth of nanoelectronvolts, the nuclear resonance natural level width.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Magnetism on ideal triangular lattices in NaBaYb(BO 3 ) 2

We report the anisotropic magnetic properties of single crystals of the triangular lattice magnet NaBaYb(BO 3 ) 2 . In this material, a layered [Yb(BO 3 ) 2 ] ∞ framework is sandwiched by Na + or Ba 2+ layers in alternation. The space group is centrosymmetric, R3¯m, with no detectable disorder and Yb 3+ -based easy axis Kramers doublets forming layered triangular lattice planes. A specific-heat anomaly indicates a second-order phase transition at T = 0.41(2)K that is suppressed to less than 0.15 K in a 0.1-T magnetic field. With a change in entropy of only 0.6(2)% of R ln 2 at this transition, NaBaYb(BO 3 ) 2 , however, retains 94(1)% of R ln 2 entropy to the lowest temperature accessed (T = 0.15K). As a result, strong frustration and the potential for quantum magnetism are implied.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Lanthanum and neodymium solubility in simplified SiO{sub 2}-B{sub 2}O{sub 3}-Na{sub 2}O-Al{sub 2}O{sub 3}-CaO high level waste glass

Lanthanum and neodymium incorporation in simplified high level waste glasses has been investigated for SiO{sub 2}B{sub 2}O{sub 3}Na{sub 2}OAl{sub 2}O{sub 3}CaO compositions quenched from 1200 degrees C, for varying La /(La + Nd) (atomic) and increasing rare-earth oxides contents. In this system and beyond the solubility limit, rare-earths (RE) elements are reported to form apatite phases with the general formula Ca{sub 2}RE{sub 8}(SiO{sub 4}){sub 6}O{sub 2}. In the current study, speciation of these trivalent RE{sup 3+} cations in both amorphous network and crystal phases was determined from X-ray diffraction, scanning electron microscopy, optical absorption at 10 K, Raman spectroscopy, and electron probe microanalysis. It appeared that RE{sub 2}O{sub 3} solubility was higher for La -rich formulations than for Nd -rich ones and that an increase in the RE oxide content reduces the connectivity of the network building units through formation of non-bridging oxygens at the expense of the oxygen bridges. This depolymerization of the glass network did not affect neodymium environment which consisted in silicate tetrahedra. The composition of the apatite crystals was found to be affected by the La /(La + Nd) of the parent glass and deviation from the ideal composition (Ca{sub 2}RE{sub 8}(SiO{sub 4}){sub 6}O{sub 2}) occurred in the neodymium end of the system. It thus appears that both RE{sub 2}O{sub 3} solubility and crystal composition are strongly dependent on the type and crystal chemistry of the RE elements. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Comparison of B{sub 2}O{sub 3} and BN deposited by atomic layer deposition for forming ultrashallow dopant regions by solid state diffusion

In this study, the authors investigated atomic layer deposition (ALD) of B{sub 2}O{sub 3} and BN for conformal, ultrashallow B doping applications and compared the effect of dopant-containing overlayers on sheet resistance (R{sub s}) and B profiles for both types of films subjected to a drive-in thermal anneal. For the deposition of B{sub 2}O{sub 3}, tris(dimethylamido)borane and O{sub 3} were used as coreactants and for the deposition of BN, BCl{sub 3} and NH{sub 3} were used as coreactants. Due to the extreme air instability of B{sub 2}O{sub 3} films, physical analysis was performed on B{sub 2}O{sub 3} films, which were capped in-situ with ∼30 Å ALD grown Al{sub 2}O{sub 3} layers. For the BN films, in-situ ALD grown Si{sub 3}N{sub 4} capping layers (∼30 Å) were used for comparison. From spectroscopic ellipsometry, a thickness decrease was observed after 1000 °C, 30 s anneal for the B{sub 2}O{sub 3} containing stack with 60 ALD cycles of B{sub 2}O{sub 3}, whereas the BN containing stacks showed negligible thickness decrease after the annealing step, regardless of the number of BN cycles tested. The postanneal reduction in film thickness as well as decrease in R{sub s} for the B{sub 2}O{sub 3} containing stack suggests that the solid state diffusion dopant mechanism is effective, whereas for the BN containing stacks this phenomenon seems to be suppressed. Further clarification of the effectiveness of the B{sub 2}O{sub 3} containing layer compared to the film stacks with BN was evidenced in backside secondary ion mass spectrometry profiling of B atoms. Thus, B{sub 2}O{sub 3} formed by an ALD process and subsequently capped in-situ followed by a drive-in anneal offers promise as a dopant source for ultrashallow doping, whereas the same method using BN seems ineffective. An integrated approach for B{sub 2}O{sub 3} deposition and annealing on a clustered tool also demonstrated controllable R{sub s} reduction without the use of a capping layer.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Flux Growth, Thermal Properties, and Luminescence Spectra of (Er,Yb,Lu)Al{sub 3}(BO{sub 3}){sub 4} Solid Solutions

We have studied phase relations in the pseudoquaternary system LuAl{sub 3}(BO{sub 3}){sub 4}–(K{sub 2}Mo{sub 3}O{sub 10}–Al{sub 2}O{sub 3}–B{sub 2}O{sub 3}) in the temperature range 1130 to 900°C. The phase relations were represented in graphical form, as a projection of the formation of solid phases in this range onto the composition triangle at 900°C. Optimal results in terms of high-temperature solution growth have been obtained at 25 wt % LuAl{sub 3}(BO{sub 3}){sub 4} in the growth charge. Undoped and erbium–ytterbium codoped LuAl{sub 3}(BO{sub 3}){sub 4} (LuAB) single crystals have been grown from high-temperature solutions on “pointlike” seeds. The (Er,Yb):LuAB crystals are similar in thermal properties and luminescence spectra to (Er,Yb):YAl{sub 3}(BO{sub 3}){sub 4} and (Er,Yb):GdAl{sub 3}(BO{sub 3}){sub 4} crystals and can be used in diode-pumped lasers operating in the nominally eye-safe spectral region 1.5–1.6 μm.

36 MATERIALS SCIENCE↗
DOE OSTI2018

High-Temperature Raman Scattering Study of the Li{sub 2}O–B{sub 2}O{sub 3}–MoO{sub 3} System: I. Detailed Comparison of the Structures of Molten Lithium and Potassium Molybdates

The structure and polymerization behavior of molybdenum–oxygen groups in molten lithium and potassium molybdates with different alkali-metal oxide to molybdenum oxide ratios have been studied by high-temperature Raman spectroscopy. The results are analyzed in comparison with the structural units of pure molybdenum oxide.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Crystallization, crystal-structure refinement, and IR spectroscopy of a synthetic hexahydroborite analog

The crystal structure of the hexahydroborite analog Ca[B(OH){sub 4}]{sub 2} {center_dot} 2H{sub 2}O (a = 7.9941(3) Angstrom-Sign , b = 6.6321(2) Angstrom-Sign , c = 7.9871(3) Angstrom-Sign , {beta} = 104.166(4) Degree-Sign , V = 410.58(3) Angstrom-Sign {sup 3}, sp. gr. P2/c, Z = 2, {rho}{sub calc} = 1.891 g/cm{sup 3}; Xcalibur S CCD automated diffractometer, 1196 reflections with I > 2{sigma}(I), {lambda}MoK{sub {alpha}}), which was synthesized by the hydrothermal method via the recrystallization of calciborite CaB{sub 2}O{sub 4} (M) in the M - B{sub 2}O{sub 3} - H{sub 2}O system (t = 250 Degree-Sign C and P = 70-80 atm), was refined by the least-squares method with anisotropic displacement parameters (H atoms were located; R{sub 1} = 0.0260). The structure of synthetic hexahydroborite consists of infinite columns running along the c axis. The columns are formed by Ca polyhedra linked together and to [B(OH){sub 4}] orthotetrahedra by sharing edges. Along the two other axes, the translationally equivalent columns are linked only by hydrogen bonds. The presence of a stronger bond between the discrete (Ca-B-O) columns along the shortest (b = 6.6 Angstrom-Sign ) axis accounts for the possibility of the shift of the columns by 1/2T{sub b} and the formation of the second modification of Ca[B(OH){sub 4}]{sub 2} {center_dot} 2H{sub 2}O. The crystals of synthetic hexahydroborite were studied by IR spectroscopy. A crystal-chemical analysis was performed for a series of natural metaborates with the general formula CaB{sub 2}O{sub 4} {center_dot} nH{sub 2}O (CaO: B{sub 2}O{sub 3} = 1: 1, n = 0-6), including calciborite CaB{sub 2}O{sub 4} and hexahydroborite CaB{sub 2}O{sub 4} {center_dot} 6H{sub 2}O as the end members.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Search for compounds of the NaBaR(BO{sub 3}){sub 2} family (R = La, Nd, Gd, and Yb) and the new NaBaYb(BO{sub 3}){sub 2} orthoborate

A search for compounds of the NaBaR(BO{sub 3}){sub 2} composition (where R = La{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, or Yb{sup 3+}) is performed by solid state synthesis and spontaneous crystallization. A new compound, NaBaYb(BO{sub 3}){sub 2}, is found in this series. It crystallizes in space group R3{sup -} and belongs to the family of sublayer complex orthoborates with isolated BO{sub 3} groups NaBaR(BO{sub 3}){sub 2} (R = Y, Sc, and Yb). Theoretical X-ray powder diffraction patterns of NaBaY(BO{sub 3}){sub 2}, NaBaSc(BO{sub 3}){sub 2}, and NaBaYb(BO{sub 3}){sub 2} are calculated based on single-crystal data.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Spectroscopic manifestations of local crystal distortions in excited 4f states in crystals of huntite structure

Optical absorption spectra of YbAl{sub 3}(BO{sub 3}){sub 4}, TmAl{sub 3}(BO{sub 3}){sub 4} and TbFe{sub 3}(BO{sub 3}){sub 4} trigonal crystals have been studied in temperature range 2-300 K. Temperature behavior of absorption lines parameters has shown, that during some f-f transitions the local environment of rare earth ions undergo distortions, which are absent in the ground state.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Crystal structure of a new chain diborate TmH[B{sub 2}O{sub 5}] and its comparison with related compound GdH[B{sub 2}O{sub 5}] based on the pseudosymmetry and the group-subgroup relation

Crystals of a new rare-earth chain diborate TmH[B{sub 2}O{sub 5}], space group C2/c, are obtained under hydrothermal conditions. The structure is determined without preliminary knowledge of the chemical formula. It is close to that of the GdH[B{sub 2}O{sub 5}] diborate studied earlier, but has a different orientation of the monoclinicity axis. In both structures the arrangement of atoms follows the pattern of the orthorhombic pseudosupergroup Cmca, which is most distinctly violated by the displacements of the rare-earth atoms. Their common anionic chain radical consists of diborate groups, namely, BO{sub 3} triangles and BO{sub 4} tetrahedra, 2[1T + 1{Delta}]. It is shown that the existence of two varieties that are based on the hypothetical orthorhombic prototype is determined by the pseudosymmetry and the difference between the ionic radii of the elements located at the middle and the end of the rare-earth series. The twinning and poor quality of the crystals are related to the effect of the m pseudoplane of the supergroup and cleavage. The structures of natural megaborates that contain diborate chains in complex boron-oxygen radicals are discussed.

36 MATERIALS SCIENCE↗