Search results for "Electron diffraction"

TEM studies on La2−2xCa1+2xMn2O7 (x=0.5 and 0.25)

2003

The nominal compositions and structures of the compounds La2-2xCa1+2xMn2O7 (x=0.5 and 0.25) prepared by solid-state reaction have been studied by transmission electron microscopy and high-resolution electron microscopy. Besides the observation of the major phase of a two-layer structure in the nominal composition La1.0Ca2.0Mn2O7, the embedded n = 3, n = 4 Ruddlesden-Popper phases and La rich phase in the two-layer structure were observed as defects. No layered structure was observed in the nominal composition La1.5Ca1.5Mn2O7. Instead, a major phase of orthorhombically distorted perovskite, a minor phase of an ideal cubic perovskite, and a small fraction of calcium-oxide were observed in the…

Submicrometer CaCuO2 and Ca2CuO3 particles from bimetallic formate precursors

1992

Abstract CaCuO2 and Ca2CuO3 are readily obtained by thermal decomposition of two new calcium and copper formates, CaCu(HCOO)4 and Ca2Cu(HCOO)6. These chemical-precursor based syntheses, while overcoming problems related to the stoichiometry of the final products, involve very short diffusion path lengths. This, in turn, results in soft treatments yielding pure phases constituted by submicrometer (≈0.4 μm) homogeneous particles.

Solving Challenging Crystallographic Problems with Automated Electron Diffraction Tomography (ADT)

2016

Structural Characterization of Organics Using Manual and Automated Electron Diffraction

2010

In the last decade the importance of transmission electron microscopic studies has become increasingly important with respect to the characterization of organic materials, ranging from small organic molecules to polymers and biological macromolecules. This review will focus on the use of transmission electron microscope to perform electron crystallography experiments, detailing the approaches in acquiring electron crystallographic data. The traditional selected area approach and the recently developed method of automated diffraction tomography (ADT) will be discussed with special attention paid to the handling of electron beam sensitive organic materials.

k-resolved electronic properties of ternary heavy fermion systems

1998

Total-scattering pair-distribution function of organic material from powder electron diffraction data.

2014

AbstractThis paper shows that pair-distribution function (PDF) analyses can be carried out on organic and organometallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction and nanodiffraction in transmission electron microscopy or nanodiffraction in scanning transmission electron microscopy modes. The methods were demonstrated on organometallic complexes (chlorinated and unchlorinated copper phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrat…

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.

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 BrHfNNHfBr stacked along c that are separated by a Van der Waals gap. The haf…

Ab initio structure determination and quantitative disorder analysis on nanoparticles by electron diffraction tomography.

2017

Nanoscaled porous materials such as zeolites have attracted substantial attention in industry due to their catalytic activity, and their performance in sorption and separation processes. In order to understand the properties of such materials, current research focuses increasingly on the determination of structural features beyond the averaged crystal structure. Small particle sizes, various types of disorder and intergrown structures render the description of structures at atomic level by standard crystallographic methods difficult. This paper reports the characterization of a strongly disordered zeolite structure, using a combination of electron exit-wave reconstruction, automated diffrac…