7 research outputs found
Acquisition of high-quality three-dimensional electron diffuse scattering data
The diffraction patterns of crystalline materials with local order contain
sharp Bragg reflections as well as highly structured diffuse scattering. The
instrumental requirements, experimental parameters and data processing
techniques for obtaining high-quality diffuse scattering data have previously
been determined for X-ray and neutron diffraction, but not yet for electron
diffraction. In this study, we show that the spatial resolution of the diffuse
scattering in three-dimensional electron diffraction (3D ED) data depends on
various effects, including the convergence of the electron beam, the point
spread function of the detector and the crystal mosaicity. In contrast to
single-crystal X-ray diffraction, the detector point spread function for 3D ED
is broader for a hybrid pixel detector than for a CCD. In our study, we also
compare the diffuse scattering in 3D ED data with the diffuse scattering in
single-crystal X-ray diffraction data and show that the diffuse scattering in
3D ED data can be obtained with a quality comparable to that from
single-crystal X-ray diffraction. As electron diffraction requires much smaller
crystal sizes than X-ray diffraction, this opens up the possibility to
investigate the local structure of many technologically relevant materials for
which no crystals large enough for single-crystal X-ray diffraction are
available
Python script to calculate the R-value.
<p>Python script to calculate the R-value (agreement factor between 2D/3D calculated and experimental data). </p>
Quantitative analysis of diffuse electron scattering in the lithium-ion battery cathode material <tex>Li_{1.2}Ni_{0.13}Mn_{0.54}Co_{0.13}O_{2}$</tex>
Determination of Spinel Content in Cycled Li1.2Ni0.13Mn0.54Co0.13O2 Using Three-Dimensional Electron Diffraction and Precession Electron Diffraction
Among lithium battery cathode materials, Li1.2Ni0.13Mn0.54Co0.13O2 (LR-NMC) has a high theoretical capacity, but suffers from voltage and capacity fade during cycling. This is partially ascribed to transition metal cation migration, which involves the local transformation of the honeycomb layered structure to spinel-like nano-domains. Determination of the honeycomb layered/spinel phase ratio from powder X-ray diffraction data is hindered by the nanoscale of the functional material and the domains, diverse types of twinning, stacking faults, and the possible presence of the rock salt phase. Determining the phase ratio from transmission electron microscopy imaging can only be done for thin regions near the surfaces of the crystals, and the intense beam that is needed for imaging induces the same transformation to spinel as cycling does. In this article, it is demonstrated that the low electron dose sufficient for electron diffraction allows the collection of data without inducing a phase transformation. Using calculated electron diffraction patterns, we demonstrate that it is possible to determine the volume ratio of the different phases in the particles using a pair-wise comparison of the intensities of the reflections. Using this method, the volume ratio of spinel structure to honeycomb layered structure is determined for a submicron sized crystal from experimental three-dimensional electron diffraction (3D ED) and precession electron diffraction (PED) data. Both twinning and the possible presence of the rock salt phase are taken into account. After 150 charge–discharge cycles, 4% of the volume in LR-NMC particles was transformed irreversibly from the honeycomb layered structure to the spinel structure. The proposed method would be applicable to other multi-phase materials as well
Determination of spinel content in cycled <tex>Li_{1.2}Ni_{0.13}Mn_{0.54}Co_{0.13}O_{2}$</tex> using three-dimensional electron diffraction and precession electron diffraction
Poly[(μ4-phenylphosphonato)zinc(II)]
The title two-dimensional coordination polymer, [Zn(C6H5PO3)]n, was
synthesized serendipitously by reacting a tetraphosphonate cavitand
Tiiii[C3H7, CH3, C6H5] and Zn(CH3COO)22H2O in a DMF/H2O mixture. The
basic conditions of the reaction cleaved the phosphonate bridges at the upper
rim of the cavitand, making them available for reaction with the zinc ions. The
coordination polymer can be described as an inorganic layer in which zinc
coordinates the oxygen atoms of the phosphonate groups in a distorted
tetrahedral environment, while the phenyl groups, which are statistically
disordered over two orientations, point up and down with respect to the layer.
The layers interact through van der Waals interactions. The crystal studied was
refined as a two-component twin