A5089911202- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Advancements in Battery Materials
- Crystal Structures and Properties
- Nuclear materials and radiation effects
- Chemical Synthesis and Characterization
- High-pressure geophysics and materials
- Solid-state spectroscopy and crystallography
- Advanced Battery Materials and Technologies
- Crystallography and molecular interactions
- Magnetic and transport properties of perovskites and related materials
- Advancements in Solid Oxide Fuel Cells
- Nuclear Physics and Applications
- Perovskite Materials and Applications
- Advanced Condensed Matter Physics
- Microwave Dielectric Ceramics Synthesis
- Concrete and Cement Materials Research
- Advanced ceramic materials synthesis
- Inorganic Fluorides and Related Compounds
- Electrical and Thermal Properties of Materials
- Chalcogenide Semiconductor Thin Films
- Ionic liquids properties and applications
- Electron and X-Ray Spectroscopy Techniques
- Electronic and Structural Properties of Oxides
- Inorganic Chemistry and Materials
National Research Council Canada
2006-2024
University of Glasgow
2024
Oak Ridge National Laboratory
2014-2018
Paul Scherrer Institute
2018
Brookhaven National Laboratory
2017
Oak Ridge Associated Universities
2017
Spallation Neutron Source
2016
National Academies of Sciences, Engineering, and Medicine
2002-2013
McMaster University
2010
University of Antwerp
2010
Abstract We have examined the crystal structures and structural phase transitions of deuterated, partially deuterated hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI 3 ) using time-of-flight neutron synchrotron X-ray powder diffraction. Near 330 K high temperature cubic phases transformed to a body-centered tetragonal phase. The variation order parameter Q for this transition scaled with T as ∼ (T c −T) β , where is critical exponent was close ¼, predicted...
Optimizing properties of phosphors for use in white-light-emitting diodes (WLEDs) is an important materials challenge. Most have a low level lattice disorder due to mismatch between the host and activator cations. Here we show that deliberate introduction high levels cation leads significant improvements quantum efficiency, stability thermal quenching, emission lifetime Sr1.98–x(Ca0.55Ba0.45)xSi5N8:Eu0.02 (x = 0–1.5) phosphors. Replacing Sr by (Ca0.55Ba0.45) mixture with same average radius...
The neutron powder diffractometer POWGEN at the Spallation Neutron Source has recently (2017-2018) undergone an upgrade which resulted in increased detector complement along with a full overhaul of structural design instrument. current instrument solid angular coverage 1.2 steradians and maintains original third-generation concept, providing single-histogram data set over wide d-spacing range high resolution to access large unit cells, detailed refinements situ/operando measurements.
We have investigated the electronic and atomic structure of a manganese-chromium-based layered oxide material during electrochemical cycling using in situ X-ray absorption spectroscopy. Our results indicate that charge compensation cathode is achieved by oxidation/reduction octahedral Cr(III) ions to tetrahedral Cr(VI) delithiation/lithiation. Manganese are present predominantly Mn(IV) oxidation state do not appear actively participate process. To accommodate large changes coordination...
We report on the synthesis and characterization of a new metastable polymorph Li2MnSiO4 adopting Pn space group, prepared by ion-exchange from Na2MnSiO4. Density-functional theory methods were used to predict lattice parameters atom positions material those Na2MnSiO4 LiNaMnSiO4, allowing their identification X-ray diffraction profiles, as well comparison measured calculated cell parameters. The electrochemical activity this cathode for lithium ion batteries was evaluated in coin cells...
It is demonstrated that Na ions are mobile at room temperature in the nitridophosphate compound Na3TiP3O9N, with a diffusion pathway calculated to be fully three-dimensional and isotropic. When used as cathode Na-ion batteries, Na3TiP3O9N has an average voltage of 2.7 V vs Na+/Na cycles good reversibility through mechanism appears single solid solution process without any intermediate plateaus. X-ray neutron diffraction studies well first-principles calculations indicate volume change occurs...
The low energy spin excitation spectrum of the breathing pyrochlore ${\mathrm{Ba}}_{3}{\mathrm{Yb}}_{2}{\mathrm{Zn}}_{5}{\mathrm{O}}_{11}$ has been investigated with inelastic neutron scattering. Several nearly resolution limited modes no observable dispersion are observed at 250 mK while, elevated temperatures, transitions between excited levels become visible. To gain deeper insight, a theoretical model isolated ${\mathrm{Yb}}^{3+}$ tetrahedra parametrized by four anisotropic exchange...
The remarkable effect that secondary bonding interactions can have on the macroscopic properties of a material is illustrated by two polymorphs title compound. phase which most stable under ambient pressure and temperature consists puckered supramolecular ribbon polymers assembled Te--N displays characteristic red-orange color. A second yellow ribbons with alternating short long intermolecular distances metastable; at 127 °C undergoes an exothermic irreversible transition to red polymorph....
Abstract The effect of carbon dioxide (CO 2 ) on the physical properties poly( L ‐lactic acid) (PLLA) and formation crystalline domains was investigated. presence CO in matrix found to induce crystallization PLLA, with crystallinity increasing pressure. combination saturation conditions studied for its porous morphologies PLLA. Moreover, PLLA structures further exploited by first creating samples using at various pressures 25 °C then re‐saturating same a constant pressure 2.8 MPa 0 °C. This...
Oxygen storage materials (OSMs) provide lattice oxygen for a number of chemical-looping reactions including natural gas combustion and methane reforming. La1–xSrxFeO3−δ has shown promise use as an OSM in reforming due to its high product selectivity, fast oxide diffusion, cycle stability. Here, we investigate the structural evolution series x = 0, 1/3, 1/2, 2/3, 1, using situ synchrotron X-ray neutron diffraction, it is cycled under conditions reactor (methane atmospheres). In compositions...
Organolead halide perovskites are a family of hybrid organic-inorganic compounds whose remarkable optoelectronic properties have been under intensive scrutiny in recent years. Here we use inelastic x-ray scattering to study low-energy lattice excitations single crystals methylammonium lead iodide and bromide perovskites. Our findings confirm the displacive nature cubic-to-tetragonal phase transition, which is further shown, using neutron diffraction, be close tricritical point. Lastly,...
The Spallation Neutron Source at Oak Ridge National Laboratory, USA, ushered in a new era of neutron scattering experiments through the use event-based data. Tagging each event allows pump–probe experiments, measurements with parameter asynchronous to source, continuously varying parameters and novel ways testing instrument components. This contribution will focus on few examples. A pulsed magnet has been used study diffraction under extreme fields. Continuous ramping temperature is becoming...
This work is an experimental study of intrinsic point defects in off-stoichiometric kesterite type CZTSe by means neutron powder diffraction. We revealed the existence copper vacancies (VCu), various cation anti site (CuZn, ZnCu, ZnSn, SnZn, and CuZn), as well interstitials (Cui, Zni) a wide range polycrystalline samples synthesized solid state reaction. The results show that present agree with off-stoichiometry model, assuming certain substitutions accounting for charge balance. In addition...
This paper reports on specific open and interconnected CO(2) foams of poly(L-lactic acid). The effect varying gas concentration hence physical changes induced by has been investigated thus used to generate structures. developed morphologies have a skin core structure with larger pores in the smaller skin.
In this work, we examine the reaction mechanisms driven by lithiation of Li1+δMn2O4 (0 ≤ δ 1) spinels via in operando neutron powder diffraction (NPD). New are proposed involving solid-solution regions within both cubic and tetragonal spinel phases addition to a continuous phase transition between them. NPD is an ideal tool follow light elements such as lithium oxygen cathode materials which often key fully understand their structural evolutions. Here, report novel methodology prepare...
The use of microwave irradiation is already established in sample preparation for analytical work [P. J. Walter, S. Chalk, and H. M. Kingston, Microwave‐Enhanced Chemistry, Fundamentals, Sample Preparation Application, p. 55, American Chemical Society, Washington, DC (1997).] solution synthesis organic compounds (G. Majetich K. Wheless, ibid., 455). microwaves solid‐state a fairly recent development but promises advantages speed energy efficiency. This paper presents results from feasibility...
Experimental structure refinements and ab initio simulation results for 18 published, fully ordered P 6 3 / m (A^{\rm I}_4)(A^{\rm II}_6)( B O 4 ) X 2 apatite end-member compositions have been analyzed in terms of a geometric crystal-chemical model that allows the prediction unit-cell parameters ( c all atom coordinates. To an accuracy ± 0.025 Å, magnitude was reproduced from characterizing chains …– A II –O3–B–O3– –... atoms, whereas determined those describing I )–( polyhedral...