Search results for " diffraction"
showing 10 items of 896 documents
Structure characterization of hard materials by precession electron diffraction and automatic diffraction tomography: 6H-SiC semiconductor and Ni1+xT…
2012
Using a combination of automated diffraction tomography and precession electron diffraction techniques, quasi-kinematical electron diffraction data sets were collected from intermetallic Ni1+xTe1 embedded nanodomains and ion-thinned specimens of 6H–SiC semiconductor. Cell parameters and space groups were found automatically from the reconstructed 3D diffraction volume. The extracted intensities were used for fast ab initio structure determination by direct methods.
Structure analysis of side chain liquid crystal polymer films by means of electron microscopy
1987
Abstract Using the combined techniques of electron diffraction, bright and dark field electron microscopy as well as light microscopy, it has been possible to obtain detailed structural information about the arrangement of the smectic layers in a polymethacrylate side chain liquid crystal polymer with a biphenylester as the mesogenic group.
Blue-luminescent organic lead bromide perovskites: highly dispersible and photostable materials
2015
The preparation of a blue-luminescent and photostable organic–inorganic hybrid perovskite with an X-ray powder diffraction spectrum consistent with a two-dimensional inorganic framework is reported. This perovskite can be produced with a high reaction yield and valuable optical properties, such as luminescence quantum yield over 20%, radiative rate constant of up to 80 × 106 s−1, and high photostability under UV light. This material remains stable as a solid, is toluene-dispersible, and can be reverted reversibly into its precursors by using dimethylformamide (DMF). Moreover, the DMF dispersion can be injected into toluene to produce a nanomaterial or be used to prepare films by spin-coatin…
Electrodeposition of supported gadolinium-doped ceria solid solution nanowires
2012
Gadolinium-ceria solid solution nanowires with tunable composition have been prepared through template cathodic electrodeposition from solutions containing Ce 3+Gd 3+ in a variable ratio. The employed template is Porous Anodic Alumina because it can function as thermal resistant separator supporting the nanowires if used as ionic conductor in Solid Oxide Fuel Cell (SOFC). Scanning Electron Microscopy of the deposited nanostructures revealed that the use of ethanol as solvent and metal chloride as electrolyte allowed to prepare continuous, compact and well defined nanowires with morphological features stable even after thermal treatment. EDX compositional analysis confirms the presence of bo…
Multi-temperature synchrotron PXRD and physical properties study of half-Heusler TiCoSb.
2010
Phase pure samples of the half-Heusler material TiCoSb were synthesised and investigated. Multi-temperature synchrotron powder X-ray diffraction (PXRD) data measured between 90 and 1000 K in atmospheric air confirm the phase purity, but they also reveal a decomposition reaction starting at around 750 K. This affects the high temperature properties since TiCoSb is semiconducting, whereas CoSb is metallic. Between 90 K and 300 K the linear thermal expansion coefficient is estimated to be 10.5 × 10(-6) K(-1), while it is 8.49 10(-6) K(-1) between 550 K and 1000 K. A fit of a Debye model to the Atomic Displacement Parameters obtained from Rietveld refinement of the PXRD data gives a Debye tempe…
Preparation and characterization of Pd2Sn nanoparticles
2007
We report a non-aqueous solution preparation of Pd{sub 2}Sn nanoparticles with sizes near 20 nm. The intermetallic compound with the Co{sub 2}Si structure has been characterized using transmission electron microscopy, Rietveld refinement of synchrotron X-ray and neutron powder diffraction, and real-space pair distribution function analysis of high-energy synchrotron X-ray scattering. We also present a description of the electronic structure of this covalent intermetallic using density functional calculations of the electronic structure.
Rietveld refinement study of vanadium distribution in V+4–ZrSiO4 solid solutions obtained from gels
2002
Abstract Vanadium-containing zircon gel precursors with nominal compositions Vx–ZrSiO4 with x=0.0, 0.004, 0.01, 0.04 and 0.2 were prepared by a previously reported colloidal sol-gel technique and annealed for 30 h at 1400 °C. The Rietveld refinement of the structures by X-ray powder diffraction confirms previous results concerning the limit of solubility of V+4 in the zircon structure. The new finding regarding with the entry of V+4 in the Zr+4 site for zircon doped with high contents of vanadium is in accordance with reported results.
Crystal structures of superconducting sodium intercalates of hafnium nitride chloride
2006
Sodium intercalation compounds of HfNCl have been prepared at room temperature in naphtyl sodium solutions in tetrahydrofuran and their crystal structure has been investigated by Rietveld refinement using X-ray powder diffraction data and high-resolution electron microscopy. The structure of two intercalates with space group Rm and lattice parameters a = 3.58131(6) A u , c = 57.752(6) A u , and a = 3.58791(8) A u , c = 29.6785(17) A u is reported, corresponding to the stages 2 and 1, respectively, of NaxHfNCl. For the stage 2 phase an ordered model is presented, showing two crystallographically independent (HfNCl) units with an alternation of the Hf-Hf interlayer distance along the c-axis, …
Synthesis and crystal structure of the α polytype of HfNBr
2002
Abstract α-HfNBr has been prepared at 760 °C in a sealed evacuated fused silica tube by reaction between NH4Br and Hf followed by purification through chemical vapour transport under a temperature gradient. The crystal structure of this compound at room temperature has been determined for the first time by Rietveld refinement of X-ray powder diffraction data, electron diffraction and high resolution electron microscopy. It crystallises in the orthorhombic space group Pmmn with the unit cell parameters a=4.1165(2), b=3.5609(2), c=8.6440(3) A. α-HfNBr is isotypic to FeOCl and is built from layers of composition BrHfNNHfBr stacked along c that are separated by a Van der Waals gap. The haf…
X-ray powder diffraction and LIESST-effect of the spin transition material [Fe(bpp)2](NCS)2·2H2O
2006
Abstract We have studied the X-ray powder diffraction of the spin transition material [Fe(bpp)2](NCS)2 · 2H2O (bpp: 2,6-bis(pyrazol-3-yl)pyridine) at room temperature. Two crystallographic phases have been observed depending on the sample history of this material. The results obtained corroborate the earlier observations from magnetic and calorimetric studies. Relatively prolonged exposure of the sample to X-rays caused a structural change. LIESST and Reverse-LIESST effects, characterised by 57Fe Mossbauer spectroscopy, have been observed in this material.