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Results for “BISMUTH COMPOUNDS”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Stabilizing new bismuth compounds in thin film form [Stabilizing new thin film materials in bismuth compounds]

Growth of unexpected phases from a composite target of BiFeO 3 :BiMnO 3 and/or BiFeO 3 :BiCrO 3 has been explored using pulsed laser deposition. The Bi 2 FeMnO 6 tetragonal phase can be grown directly on SrTiO 3 (STO) substrate, while two phases (S1 and S2) were found to grow on LaAlO 3 (LAO) substrates with narrow growth windows. However, introducing a thin CeO 2 buffer layer effectively broadens the growth window for the pure S1 phase, regardless of the substrate. Moreover, we discovered two new phases (X1 and X2) when growing on STO substrates using a BiFeO 3 :BiCrO 3 target. Pure X2 phase can be obtained on CeO 2 -buffered STO and LAO substrates. This work demonstrates that some unexpected phases can be stabilized in a thin film form by using composite perovskite BiRO 3 (R = Cr, Mn, Fe, Co, Ni) targets. Moreover, it also indicates that CeO 2 can serve as a general template for the growth of bismuth compounds with potential room-temperature multiferroicity.

36 MATERIALS SCIENCE↗
DOE OSTI2022

An approach towards plastic scintillators from thermally activated delayed fluorescent dyes and cross-linkable bismuth compounds

Cross-linked polyvinyltoluene (PVT) based plastic scintillators loaded with dyes exhibiting thermally activated delayed fluorescence (TADF) and various amounts of (caproate)di-(methacrylate) bismuth (CMB) were developed. The co-polymerization of vinyl toluene monomer loaded with different weight ratios of CMB and 1 wt% of TADF dye yielded highly transparent cross-linked plastic scintillators with intense green photoluminescence. The thermal and mechanical properties of the scintillators were investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and micro indentation techniques. Here, their performance for radiation detection was assessed by performing gamma spectroscopy using a Cs-137 source and benchmarked to commercial plastic scintillators. The loading of CMB was guided by Monte Carlo N-Particle (MCNP) simulations. The results of this study show that the cross-linking approach and the use of TADF dyes yield scintillators with good mechanical properties with a uniaxial yield strength up to ~66 MPa for compositions loaded with 40 wt% of CMB and high optical quality. However, the light yield in gamma spectroscopy experiments is found to be reduced with the addition of CMB, suggesting a trade-off between mechanical yield strength and light yield in gamma spectroscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1972

Investigation of crystal growth in zero gravity environment and investigation of metallic whiskers

Theoretical and experimental work reported relates to the effects of near-zero gravity on growths of crystals and metallic whiskers during Skylab and Apollo flight experiments. Studies on growth and characterization of candidate materials for flight experiments cover indium-bismuth compounds, bismuth single crystals, gallium arsenide films and single crystals, and cadmium whiskers.

Davis, J. H.↗
DOE OSTI2016

Prediction of superconducting iron–bismuth intermetallic compounds at high pressure

The synthesis of materials in high-pressure experiments has recently attracted increasing attention, especially since the discovery of record breaking superconducting temperatures in the sulfur–hydrogen and other hydrogen-rich systems. Commonly, the initial precursor in a high pressure experiment contains constituent elements that are known to form compounds at ambient conditions, however the discovery of high-pressure phases in systems immiscible under ambient conditions poses an additional materials design challenge. We performed an extensive multi component ab initio structural search in the immiscible Fe–Bi system at high pressure and report on the surprising discovery of two stable compounds at pressures above ≈36 GPa, FeBi 2 and FeBi 3 . According to our predictions, FeBi 2 is a metal at the border of magnetism with a conventional electron–phonon mediated superconducting transition temperature of T c = 1.3 K at 40 GPa.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electrode designs for high energy density, efficiency, and capacity in rechargeable alkaline batteries

A secondary alkaline battery includes an anode, a cathode, and an electrolyte. The cathode includes a current collector, a cathode mixture in electrical contact with the current collector. The cathode mixture comprises: manganese oxide, a copper compound comprising copper, a salt of copper, an alloy thereof, or any combination thereof, a bismuth compound comprising bismuth, a salt of bismuth, or any combination thereof, and a conductive carbon. The secondary alkaline battery can also include a first composition in contact with the current collector and disposed between the current collector and the cathode mixture that includes copper, a salt of copper, an alloy thereof, or a combination thereof.

Yadav, Gautam G.↗
DOE OSTI2019

Local Magnetic Fields in Diamagnetic BiSbO{sub 4} and Bi{sub 4}Si{sub 3}O{sub 12}: {sup 209}Bi NQR

Local magnetic fields H{sub loc} exceeding significantly the magnetic fields produced by nuclear magnetic moments (a few gauss) have been detected in bismuth compounds with valence s and p electrons, which are generally believed to be diamagnetic, by the methods based on measuring the parameters of nuclear quadrupole interactions. Anomalies in the magnetic properties of BiSbO{sub 4} and Bi{sub 4}Si{sub 3}O{sub 12} were clearly manifested when analyzing the line shapes in their {sup 209}Bi NQR spectra. The quartet of lines for the lower transition ν{sub 1} (Δm = 1/2–3/2) in the spectrum of Bi{sub 4}Si{sub 3}O{sub 12} in zero external magnetic field and the doublets for the lines of all other transitions in the spectrum of BiSbO{sub 4} at unique crystallographic positions of bismuth atoms in the crystal lattices of the compounds suggest a magnetic nature of the splittings. The most probable values of H{sub loc} in these compounds are those in the range from 40 to 100 G.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Molecular structure models of amorphous bismuth and cerium carboxylate catalyst precursors

As our societal need for materials and energy has grown, so has our need for catalyst processes in hydrogen production. A major function in these applications, for both homogenous and heterogeneous catalysis processes, is the synthesis of an active metal catalyst. It must first be soluble to control the physical properties of the metal being used. Recent work in metal precursors has begun to turn toward these metal carboxylate types of material. Here, structural models are proposed for bismuth 2-ethylhexanoate and 2,2-dimethyloctanoate and cerium 2-ethylhexanoate. The bismuth compounds have been characterized at different ratios of bismuth to carboxylate as solutions of the free acids. Their structures are most consistent with a Bi 4 (RCO 2 ) 12 motif where the Bi ions are arranged in a flattened tetrahedron with Bi – Bi distances of about 4.3 Å. There is evidence for Bi – O – Bi linkages at low free acid concentrations. The cerium compound is most consistent with a linear tetracerium molecule where the Ce – Ce distances repeat at about 4.3 Å out to 16.4 Å. The models were generated by analogy with known crystal structures and compared to high-energy x-ray scattering data. To further evaluate the models, DFT calculations were made, and the equilibrium geometries were compared. The vibrational spectra calculated from those geometries are presented and compared to the experimental results. Magnetization vs. temperature data was collected on the cerium compound, and its behavior was consistent with the proposed model. A geometrical approach to determining the dimensionality and relative positions of the metal ions in these structures is presented.

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

A New Photocatalyst Bismuth Oxo Citrate: Synthesis, Characterization, and Photocatalytic Performance

A new photocatalyst bismuth oxo citrate was synthesized by facile precipitation process with calcination at 200 8C. The photocatalyst was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fouriertransform infrared (FTIR) spectroscopy, N2 sorptometry, and elemental analysis. Morphologically, it is composed of polyhedral particles with different, irregular shapes and sizes. The specific surface area (SSA) of the photocatalyst was 8.92 m2 g-1. It showed very good photocatalytic performance and reusability. Total decolorization of Reactive Blue 19 (RB19) was achieved in less than 10 minutes, which is much faster in comparison with TiO{sub 2} P25. Also, bismuth oxo citrate showed higher photocatalytic activity than other photocatalysts based on bismuth compounds reported by other authors. Optimal photocatalysis parameters were pH 2 and photocatalyst dose of 250 mg dm-3. The decolorization rate was found to decrease as initial dye concentration increased. The photocatalytic data best fitted to L-H kinetic model with pseudo-first order reaction rate. Chrastil diffusion model showed that diffusion has not influence on the process. Water Environ. Res., 90, 719 (2018). © 2018 Water Environment Federation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Low temperature structural variations of Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-7%BaTiO{sub 3} single crystal: Evidences from optical ellipsometry and Raman scattering

Optical properties and structural variations of Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-7%BaTiO{sub 3} (NBT-7%BT) single crystal have been studied by temperature-dependent optical ellipsometry and Raman spectroscopy from 4.2 to 300 K. The second derivative of the complex dielectric functions reveals two interband transitions (E{sub cp1} and E{sub cp2}) located at about 3.49 and 4.25 eV, respectively. Depending on the temperature evolution of electronic transitions, structural variations appear near 60, 150, and 240 K, respectively. These anomalies are also well illustrated from the low-frequency phonon modes involving vibrations of Bi. The low-temperature structural variations of NBT-7%BT crystal can be associated with instability of the crystalline lattice driven by off-centered Bi ions, followed by the variations of polarizability of the unit cells.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1996

Research on high Tc superconducting compounds

Mossbauer research using the 21.54 kev resonance radiation of Eu-151 on the high temperature superconductors Bi(2)Ca(0.5)Eu(0.5)Sr(2)CU2O(x), and EuBa(2)CU(3)O(7-x) is performed. For the Bismuth compound the Mossbauer measurements gave a weak signal at room temperature but improved at lower temperatures. Experimental data indicated that europium is located at only one crystallographic site. Isomer shift measurements were .69 + 0.02 mm/s with respect to EuF(3). The linewidth at room temperature was found to be 2.54 mm/s. This value falls within the values observed by other researchers on Eu based 1,2,3 high-Tc compounds. Our results also show the Eu to be trivalent with no trace of divalent europium present. Superconducting europium based 1,2,3 compounds were prepared and measurements completed. Our results show the Eu to be trivalent with no trace of divalent europium present. These compounds had an average isomer shift of .73 mm/s +/- O.02 for all samples made. One of these was irradiated with 3.5 X 10(exp 16) neutrons and a comparison made of the Mossbauer parameters for the irradiated and non-irradiated samples. Experimental results showed no difference between linewidths but a measurable effect was seen for the isomer shift.

Oliver, Frederick W.↗
DOE OSTI2015

Critical behavior and non-universal low-field magnetic scaling in La{sub 1-x}Bi{sub x}MnO{sub 3} (x=0.4 & 0.6) perovskite manganite oxide

We report on critical behavior in La{sub 1-x}Bi{sub x}MnO{sub 3} (x=0.4 & 0.6) perovskite manganite oxide by studying AC susceptibility, χ, measured at randomly chosen low magnetic fields (H=9.45 Oe to 0.95 Oe) at fixed frequency of f=131 Hz. The samples exhibit non-uniformity in their magnetic spin interactions around paramagnetic-to-ferromagnetic transition temperature (T{sub C}). By non-universal low-field magnetic scaling of AC χ given as, χ{sup −1}-χ{sup −1}(T{sub C}) ∼ (T/T{sub C}−1){sup γ} ≡ τ{sup γ} the magnetic interactions in the samples around T{sub C} has been studied. The linear fit to ln (χ{sup −1} - χ{sub C}{sup −1}) vs. ln (T/T{sub C}-1) gives the values of critical exponent ‘γ’ under applied magnetic fields. The values of γ is found to be ∼1.48±0.007 for the sample with x=0.4 and ∼1.36±0.004 for x=0.6 at 0.95 Oe lie in the context of 3D Heisenberg type spin interactions. The profound 3D Heisenberg type spin interactions arises due to the phase separation effect for x=0.4 and breaking of ferromagnetic order and induced Bi{sup 3+} (6S{sup 2}) − O{sup 2−} (2P{sup 6}) lattice distortions for x=0.6 as discussed in manuscript.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Effective Hamiltonian for surface states of topological insulator thin films with hexagonal warping

The effective Hamiltonian of the surface states on semi-infinite slabs of the topological insulators (TI) Bi{sub 2}Te{sub 3} and Bi{sub 2}Se{sub 3} require the addition of a cubic momentum hexagonal warping term on top of the usual Dirac fermion Hamiltonian in order to reproduce the experimentally measured constant energy contours at intermediate values of Fermi energy. In this work, we derive the effective Hamiltonian for the surface states of a Bi{sub 2}Se{sub 3} thin film incorporating the corresponding hexagonal warping terms. We then calculate the dispersion relation of the effective Hamiltonian and show that the hexagonal warping leads distorts the equal energy contours from the circular cross sections of the Dirac cones.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Intrinsic ultrathin topological insulators grown via molecular beam epitaxy characterized by in-situ angle resolved photoemission spectroscopy

We demonstrate the capability of growing high quality ultrathin (10 or fewer quintuple layers) films of the topological insulators Bi{sub 2}Se{sub 3} and Bi{sub 2}Te{sub 3} using molecular beam epitaxy. Unlike previous growth techniques, which often pin the Fermi energy in the conduction band for ultrathin samples, our samples remain intrinsic bulk insulators. We characterize these films using in-situ angle resolved photoemission spectroscopy, which is a direct probe of bandstructure, and ex-situ atomic force microscopy. We find that the conduction band lies above the Fermi energy, indicating bulk insulating behavior with only the surface states crossing the Fermi energy. The use of a thermal cracker allows for more stoichiometric flux rates during growth, while still creating intrinsically doped films, paving the way for future improvements in growth of topological insulators.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structural and cyclic volta metric investigations on BIPBVOX solid electrolyte synthesized by ethylene glycol–citric acid sol–gel route

Samples of BIPBVOX.x (Bi{sub 2}V{sub 1–x}Pb{sub x}O{sub 5.5–x/2}) in the composition range 0.05 ≤ x ≤ 0.20 were prepared by ethylene glycol– citric acid sol–gel synthesis route. Structural investigations were carried out by X–ray diffraction, DTA. The highly conducting γ′– phase was effectively stabilized at room temperature for compositions with x ≥ 0.17. Cyclic voltammetric measurements showed reversible redox reactions of vanadium and irreversible redox reaction of Bi{sup 3+} in the BIPBVOX system during the first cathodic and anodic sweep. However, a higher stability against the reduction of Bi{sup 3+} to metallic bismuth was seen for x=0.20.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

LiBi{sub 3}S{sub 5}—A lithium bismuth sulfide with strong cation disorder

Among chalcogenide semiconductors for thermoelectric applications, alkali-metal bismuth compounds occur in many complex compositions favorable for high performance. Although LiBi{sub 3}S{sub 5} had been announced in 1977, the potential 1D lithium-ion conductor has hitherto eluded selective synthesis and structure determination. In this study, we present a solid-state route to phase-pure LiBi{sub 3}S{sub 5} powder starting from LiBiS{sub 2} and Bi{sub 2}S{sub 3}. Neutron diffractograms and lithium NMR spectra reveal its crystal structure to be a cation-disordered variety of the AgBi{sub 3}S{sub 5} type (synthetic pavonite; monoclinic, C2/m). Topological analyses and lithium NMR relaxometry suggest that correlated lithium-ion diffusion with activation energies up to 0.66(2) eV occurs along the channels in b direction including tetrahedral voids. Because of cation disorder, immobile bismuth(III) ions clog these pathways, making LiBi{sub 3}S{sub 5} a moderate to poor ionic conductor. The synthesis route reported is nonetheless promising for new lithium bismuth sulfides with, possibly ordered, structure types of the pavonite homologous series. - Graphical abstract: Phase-pure LiBi{sub 3}S{sub 5} has been synthesized and shown to crystallize in cation-disordered variety of the AgBi{sub 3}S{sub 5} type (synthetic pavonite, C2/m) using neutron diffractometry. Topological analyses and NMR relaxometry suggest that immobile Bi{sup 3+} ions clog migration channels along b, making the material a poor lithium conductor. Display Omitted - Highlights: • Phase-pure LiBi{sub 3}S{sub 5} has been synthesized using a promising solid-state route. • LiBi{sub 3}S{sub 5} crystallizes in a cation-disordered variant of the AgBi{sub 3}S{sub 5} type. • Topological analyses suggest lithium diffusion in channels along b. • NMR relaxometry finds activation energies of diffusion as high as 0.66(2) eV. • Because of disorder, LiBi{sub 3}S{sub 5} is a moderate to poor lithium-ion conductor.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗