Papers by Douglas Buttrey
World Scientific series in 20th century chemistry, Feb 1, 1995
Density measurements on large single-crystal specimens of La,NiO 4+s and Pr2Ni04+S show that oxyg... more Density measurements on large single-crystal specimens of La,NiO 4+s and Pr2Ni04+S show that oxygen nonstoichiometry arises from the presence of excess lattice oxygen. X-ray photoelectron spectra as well as X-ray absorption edge studies provide no evidence for the existence of Ni3+ in these oxygenexcess nickelates under the conditions of the measurements. Transmission electron microscopy has revealed a.novel type of exsolution process of the stoichiometric phase out of nonstoichiometric La2Ni04 during heating in COz at 870 K for 3 h. An interpretation of the results in terms of the existence of peroxide species within the conducting layers is proposed. Q 1988 Academic press, ~nc.
HAL (Le Centre pour la Communication Scientifique Directe), 2006
The interplay between crystal symmetry and charge stripe order in Pr 1.67 Sr 0.33 NiO 4 and Nd 1.... more The interplay between crystal symmetry and charge stripe order in Pr 1.67 Sr 0.33 NiO 4 and Nd 1.67 Sr 0.33 NiO 4 has been studied by means of single crystal x-ray diffraction. In contrast to tetragonal La 1.67 Sr 0.33 NiO 4 , these crystals are orthorhombic. The corresponding distortion of the NiO 2 planes is found to dictate the direction of the charge stripes, similar to the case of diagonal spin stripes in the insulating phase of La 2−x Sr x CuO 4. In particular, diagonal stripes seem to always run along the short a axis, which is the direction of the octahedral tilt axis. In contrast, no influence of the crystal symmetry on the charge stripe ordering temperature itself was observed, with T CO ϳ 240 K for La, Pr, and Nd. The coupling between lattice and stripe degrees of freedom allows one to produce macroscopic samples with unidirectional stripe order. In samples with stoichiometric oxygen content and a hole concentration of exactly 1 / 3, charge stripes exhibit a staggered stacking order with a period of three NiO 2 layers, previously only observed with electron microscopy in domains of mesoscopic dimensions. Remarkably, this stacking order starts to melt about 40 K below T CO. The melting process can be described by mixing the ground state, which has a three-layer stacking period, with an increasing volume fraction with a two-layer stacking period.
Journal of Applied Phycology, 1970
ABSTRACT A systematic investigation of the dependence of the Verwey phase transition in magnetite... more ABSTRACT A systematic investigation of the dependence of the Verwey phase transition in magnetite on the metal‐to‐oxygen ratio, by thermomagnetic analysis of the initial permeability, reveals that the transition temperature is a maximum for pure stoichiometric Fe 3 O 4 and is strongly depressed by departures from ideal stoichiometry. Homogeneous single crystalline samples were prepared by subsolidus controlled oxygen fugacity annealing at 1400 °C. Heat capacity measurements by relaxation calorimetry techniques indicate a drastic reduction in the entropy, as well as temperature, of the transition with departures from ideal stoichiometry. For high levels of cation deficiency, a second, instead of a first‐order, transition is observed.
Neutron scattering and muon spin relaxation studies of some materials related to high-T/sub c/ su... more Neutron scattering and muon spin relaxation studies of some materials related to high-T/sub c/ superconductors are described. For La/sub 2-x/Sr/sub x/CuO/sub 4/ with x as large as 0.05, our data indicate spin glass freezing with a frozen local moment of the same size as in the nominally pure (x = O) antiferromagnet. Magnetic fluctuations similar to those for La/sub 2/CuO/sub 4/ are found for La/sub 2/NiO/sub 4// which thus far has not been shown to be the parent compound of superconductor. 17 refs., 5 figs.
Meeting abstracts, 2011
In this study we demonstrate the generation of electricity at high power densities, >300 mW/cm 2 ... more In this study we demonstrate the generation of electricity at high power densities, >300 mW/cm 2 at 973 K, from a solid fuel (sugar char) in a Solid Oxide Fuel Cell (SOFC) using a molten Sb anode. The anode design is simple and capable of operating continuously on a wide range of carbonaceous fuels, including sugar, rice starch, carbon black, and graphite. The following reactions take place in the anode of this cell: 2Sb + 3O 2-↔ Sb 2 O 3 + 6e-Sb 2 O 3 + 3/2 C ↔ 2Sb + 3/2 CO 2 .
ChemInform, Aug 21, 2010
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Superconductivity, Aug 1, 1997
... The sample mosaicity was ~0 .... The growth and characterization of the single-crystal sample... more ... The sample mosaicity was ~0 .... The growth and characterization of the single-crystal sample have been described previously [3]. In order to achieve an optimal thickness of t ram, the sample was cleaved in ... 2. JM Tranquada, DJ Buttrey, V. Sachan, and JE Lorenzo, Phys, Rev. ...
Physica B-condensed Matter, Jul 1, 2000
Raman light-scattering and optical conductivity measurements of a single crystal of La Sr NiO whi... more Raman light-scattering and optical conductivity measurements of a single crystal of La Sr NiO which shows incommensurate charge ordering in a stripe phase have been carried out. The analysis of the positions, shifts and splitting of the phonon lines that are induced by charge ordering and the comparison with inelastic neutron scattering data lead to the conclusion that the charges are located on Ni-sites. The lines which appear from the (, , 0) point of Brillouin zone give unambiguous evidence of the pinning of stripes to the lattice. The magnitude of a charge gap 840 cm\ opening below ¹ "150 K is the same for both far-infrared absorption and Raman light scattering measurements. 2000 Elsevier Science B.V. All rights reserved.
Physical review, Jul 15, 1981
ABSTRACT
Journal of Crystal Growth, Jul 1, 1990
Low Temperature Physics, Jul 1, 2002
We describe the results of electronic Raman scattering experiments in two differently doped singl... more We describe the results of electronic Raman scattering experiments in two differently doped single crystals of La Sr NiO 2 4-x x (x = 0.225 and 1/3). In B g 1 symmetry a crossover from weakly interacting to pseudogap-like behavior is observed at a charge-ordering temperature T co. In B g 2 symmetry a redistribution of electronic continua with decreasing temperature is accompanied by a loss of spectral weight below T co in the low-frequency region due to opening of a pseudogap. The slope of the Raman response at vanishing frequencies is investigated, too. Its temperature behavior in B g 2 symmetry, which predominantly selects charge carriers with momenta along the diagonals of the NiO 2 bonds, provides clear evidence for one-dimensional charge transport in the charge-ordered phase.
Journal of Physical Chemistry C, Jan 27, 2010
Using high-angle annular dark-field scanning transmission electron microscopy, we investigated el... more Using high-angle annular dark-field scanning transmission electron microscopy, we investigated electron-beam-induced fragmentation (EBIF) processes in NiBi alloys. We are able to establish the presence of very small clusters of nanoparticles that eluded detection in earlier TEM work and, furthermore, confirm the existence of core-shell particles with a Bi core and a Ni-Bi shell. On the basis of these and earlier observations, we propose a general mechanism for the creation of core-shell particles using EBIF.
Journal of Electron Microscopy, Dec 4, 2008
The 'M2' phase of... more The 'M2' phase of the oxidation catalyst MoVNbTeO was studied with an aberration-corrected STEM using HAADF imaging, and three 60 degrees twin orientations were identified. Comparisons between the experimental HAADF images and image simulations suggest that the there are two different Te sites, as has been previously reported; however, there are differences between the structure proposed in DeSanto et al. (2004) Z. Kristogr. 219: 152 and the experimental HAADF images.
Journal of The Electrochemical Society, 2011
ABSTRACT Molten alloys with 50-mol% In-Sb, Sn-Sb, Sb-Bi, and Sb-Pb were examined as anodes for so... more ABSTRACT Molten alloys with 50-mol% In-Sb, Sn-Sb, Sb-Bi, and Sb-Pb were examined as anodes for solid oxide fuel cells at 973 K. The cells were operated in the battery mode, without added fuel, in order to understand the oxidation characteristics of these alloys at electrolyte interfaces. Cells using 50-mol% In-Sb and Sn-Sb mixtures exhibited open-circuit voltages (OCV) of 1.0 and 0.93 V, values that are identical to that of cell with pure In and Sn respectively. Also similar to the pure In and Sn anodes, the impedances of these cells were initially low but increased dramatically after drawing a small amount of charge, implying formation of In(2)O(3) and SnO(2) layers at the electrolyte interface. The 50-mol% Sb-Bi cell had an OCV of 0.73 V initially, close to the OCV observed with pure Sb. The OCV remained constant until a charge identical to that required for oxidation of all the Sb had been passed, after which the OCV dropped to 0.43 V, similar to the value for pure Bi. SEM analysis of the cell after conversion of the Sb showed two distinct phases, with metallic Bi at the bottom and Sb(2)O(3) at the top. The electrochemical oxidation of 50-mol% Sb-Pb alloys exhibited an OCV that changed continuously with conversion, from 0.73 V initially to 0.67 V following the addition of charge corresponding to oxidation of 120% the Sb. The total cell impedance remained low for this entire period. EDS measurements on the sectioned Sb-Pb cell suggested that both Sb and Pb were oxidized simultaneously to form a mixed oxide of Pb and Sb. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.006112jes]
Physical review, Feb 1, 1995
We present a single-crystal neutron-diffraction study of the time dependence of the interstitial ... more We present a single-crystal neutron-diffraction study of the time dependence of the interstitial oxygen ordering in La2Ni04. &O5. We have studied the kinetics of the growth of the intercalated Bmab phase at diff'erent temperatures below the phase transition temperature (= 290.5 K). The transformation appears to occur by homogeneous nucleation and growth. The time dependence of the transformed fraction follows a universal curve when the time variable is scaled appropriately. The transformation rate peaks near 265 K. The domain size measured after saturation decreases with decreasing quench temperature due to the increase in nucleation rate. We have shown recently that the nonstoichiometric compound La2Ni04+g has a very rich oxygen-content phase diagram. The incorporation of extra oxygen into the lattice is favored by distortions involving tilts of the NiOs octahedra about a [110] axis of the hightemperature tetragonal unit cell, similar to those that occur in the low-temperature orthorhombic phase (space group Bmab) for b = 0.00. Individual added oxygens will tend to sit between adjacent LaO layers at positions (- ,- ,-) of the Bmab structure. 4 However, an interstitial oxygen will repel its four oxygen nearest neighbors, causing the associated octahedra to tilt away &om it and disrupting the local tilt pattern.
Journal of Solid State Chemistry, Apr 1, 1996
ABSTRACT
Physical review, Jan 16, 2003
We characterize the local structure and correlations of charge stripes in La1.725Sr0.275NiO4 usin... more We characterize the local structure and correlations of charge stripes in La1.725Sr0.275NiO4 using transmission-electron microscopy. We present direct evidence that the stripe modulation is indeed one-dimensional within each NiO2 plane. Furthermore, we show that individual stripes tend to be either site-centered or bond-centered, with a bias towards the former. The spacing between stripes often fluctuates about the mean, contributing to a certain degree of frustration of the approximate body-centered stacking along the c-axis. These results confirm ideas inferred from previous neutrondiffraction measurements on doped nickelates, and demonstrate that charge-stripe order is quite different from the conventional concept of charge-density-wave order.
Materials Research Bulletin, Jun 1, 1986
Investigation of a variety of bismuth molybdate preparations with Bi/Mo ~ 5 by x-ray microanalysi... more Investigation of a variety of bismuth molybdate preparations with Bi/Mo ~ 5 by x-ray microanalysis and electron and x-ray powder diffraction has revealed the existence of a new phase with composition Bi38MoTO?~, which belongs to the orthorhombic system (Pccn) with = 16.818, b = 28.658, ~ = 16.903~, and Z = 4. The structure appears to be based on defect fluorite with 48 oxygen vacancies in the unit cell. Preparations with larger Bi/Mo ratios resulted in fluorite-like structures with disordered superlattices.
Physical Review Letters, Mar 6, 2002
The existence of a stripe-liquid phase in a layered nickelate, La1.725Sr0.275NiO4, is demonstrate... more The existence of a stripe-liquid phase in a layered nickelate, La1.725Sr0.275NiO4, is demonstrated through neutron scattering measurements. We show that incommensurate magnetic fluctuations evolve continuously through the charge-ordering temperature, although an abrupt decrease in the effective damping energy is observed on cooling through the transition. The energy and momentum dependence of the magnetic scattering are parametrized with a damped-harmonic-oscillator model describing overdamped spin-waves in the antiferromagnetic domains defined instantaneously by charge stripes.
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Papers by Douglas Buttrey