Special Issue "Electron Diffraction and Structural Imaging"
Deadline for manuscript submissions: 15 August 2021.
Interests: electron crystallography; precession electron diffraction; nano-materials; organic pharmaceuticals; cultural heritage materials
Interests: Electron Microscopy; Metallic nanostructures; Metal-oxides and ferroelectrics; Crystallography of interfaces
Interests: electron crystallography; minerals; porous materials; nano-materials
Over the last decade, electron diffraction (ED) and structural imaging have received renewed interest from the scientific community. This is due to the recent advances in TEM instrumentation (Cs correctors, direct detection cameras for high-throughput 3D ED, 4D STEM or serial TEM experiments) and also to the introduction of new experimental techniques, such as beam precession and ptychography. Thus, the atomic structural characterisation of various types of materials (functional materials, energy materials, zeolites, minerals, organic compounds, pharmaceuticals and proteins) has become possible at nm-scale resolution.
ED in TEM is used for the structure determination of new materials (down to 50 nm in size) and is also used to obtain phase and orientation mapping, strain mapping, determination of electric fields and the study of amorphous materials which otherwise cannot be studied using laboratory X-ray or synchrotron methods. Moreover, the development of in-situ sample holders (gas and heating, liquid etc.) has allowed the study of the structure of materials in real time under natural conditions.
In this Special Issue entitled “Electron Diffraction and Structural Imaging”, we welcome contributions covering any aspect of ED, structural imaging and other related in-situ techniques, which make use of consolidated or advanced TEM instrumentation with potential applications for a wide range of materials. Abstract Submission Deadline: 31st May, 2021.
Dr. Partha Pratim Das
Dr. Arturo Ponce-Pedraza
Dr. Enrico Mugnaioli
Dr. Stavros Nicolopoulos
Manuscript Submission Information
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- electron diffraction
- 4D STEM
- serial ED
- 3D ED
- direct detection cameras
- atomic imaging
The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.
Title: Comprehensive Study of Li+/Ni+ Anti-Site Defects in Ni-Rich Layered Cathodes for Li-Ion Batteries
Authors: Artem M. Abakumov; Elena D. Orlova; Aleksandra A. Savina; Anatolii V. Morozov
Affiliation: Center for Energy Science and Technology, Skolkovo Institute of Science and Technology, Bolshoy Boulevard 30, bld. 1, 121205 Moscow, Russia
Abstract: The layered oxides LiNixMnyCozO2 with high nickel content (x>0.6), so-called Ni-rich NMCs, are promising high-energy density positive electrode (cathode) materials for Li-ion batteries. However, the electrochemical properties of these materials strongly depend on concentration of the Li+/Ni2+ anti-site defects, originating from Li+ and Ni2+ ionic radii proximity. The most common anti-site defects evaluation method is based on powder X-ray diffraction: the defect concentration could be assessed semi-quantitatively by comparison of the a and c lattice parameters, and relative intensities of the (003) and (104) diffraction peaks; or quantitatively by the Rietveld refinement. Despite the Rietveld refinement is considered as a simple and reliable method, it does not provide the information on defects location in the NMC particles. The transmission electron microscopy techniques such as high-resolution HAADF-STEM imaging and electron diffraction tomography (EDT) allow probing the materials locally. In the present work the TEM-assisted quantitative Li+/Ni2+ anti-site defects analysis with EDT and HAADF-STEM in eight Ni-rich NMC samples with various defects content is demonstrated, and these advanced quantification methods have been validated through correlation with both PXRD semi-quantitative and quantitative parameters. Noteworthy, while PXRD and EDT methods demonstrate overall defects amount, HAADF-STEM allows to quantitatively distinguish defects’ surface and bulk contributions. Therefore, the combination of mentioned PXRD and TEM methods gives the full picture on Li+/Ni2+ anti-site defects in Ni-rich NMCs.
Keywords: Li-ion battery cathode; Ni-rich NMC; anti-site defects; transmission electron microscopy
Title: Characterization of Microstructure of Crept Nb and Ta-rich γ-TiAl Alloys by Automated Crystal Orientation Mapping and Electron Back Scatter Diffraction
Authors: Vajinder Singh, Chandan Mondal, Rajdeep Sarkar, C.M. Omprakash and P. Ghosal
Affiliation: Defence Metallurgical Research Laboratory (DMRL), Kanchanbagh, Hyderabad-500058, India
Abstract: Realization of the potential applications of Nb and Ta-rich γ-TiAl alloys critically depends on the understanding of their creep behavior. The present article reports the evolution of microstructural features in the crept γ-TiAl-based Ti–45Al–8Nb-2Cr-0.2B and Ti–45Al–8Ta-0.2C-0.2B alloys. Structural characterizations have been carried out using automated crystal orientation mapping (ACOM) along with precession electron diffraction (PED) in a transmission electron microscope in conjunction with electron back-scattered diffraction (EBSD) in a scanning electron microscope. Creep behaviour of the fourth generation γ-TiAl-based alloys has been comparatively investigated under the constant load tensile creep tests performed in the temperature range from 973 K to 1123 K and the applied stresses range of 100 MPa to 250 MPa. It has been demonstrated that the ACOM with PED technique having accurate and reliable diffraction pattern recognition and higher spatial resolution supplements effectively the conventional EBSD technique for characterization of complex microstructural features evolved during creep of multiphase (γ+α2+β)-based TiAl alloys. The results show that the Nb and Ta additions have distinctly different effects on the microstructural instability and phase transformation during the creep deformation. The formation of globular Ta-rich intermetallic phase (Ti4Al3Ta, the so-called t phase) has been noticed, preferentially along the colony and the γ-α2 interphase boundaries in the Ta-added alloy, whilst its isomorph, Ti4Al3Nb intermetallic, has not been detected in the Nb added alloy. Implications of γ-phase formation and other microstructural instabilities have been discussed with respect to the creep behavior of the two alloys.
Keywords: g-TiAl alloys; Creep; Microstructure; ACOM; EBSD
Title: Identification of Retained Austenite in 9Cr-1.4W-0.06Ta-0.12C Reduced Activation Ferritic Martensitic Steel
Authors: R. Mythili; Ravikirana; L. Herojit Singhd; R. Govindarajb; A.K. Sinhaf; M. N. Singhf; S. Saroja; M. Vijayalakshmig; S.K Debf
Affiliation: Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, 603102, India
Abstract: 9Cr RAFM steels which are candidate materials for the TBM of nuclear fusion reactors are considered to be air hardenable. However, the processing conditions play a significant role during the transformation of austenite to martensite/ferrite on cooling. This paper reports the presence of a low amount of retained austenite in normalized 9Cr-1.4W-0.06Ta-0.12C Reduced Activation Ferritic Martensitic Steel, which has been confirmed by synchrotron XRD, Mossbauer Spectroscopy and Automated Crystal Orientation Imaging Microscopy in TEM. The possible reasons for the retention of austenite are also discussed.
Keywords: Reduced Activation Ferritic Martensitic Steel; microstructure; martensite; retained austenite; ACOM-TEM; Mossbauer Spectroscopy
Title: Ruddlesden-Popper faults in the NdNiO3 film
Authors: C Yang; Y Wang; HG Wang; R Ortiz; D Putzky; E Benckiser; B Keimer; PA van Aken
Affiliation: Max Planck Institute for Solid State Research, Stuttgart, Germany
Abstract: The NdNiO3 (NNO) system attracts increasing attention due to the recent discovery of superconductivity in Nd0.8Sr0.2NiO2. In NNO, Ruddlesden-Popper (RP) faults play an important role in its functional properties, motivating our exploration for its microstructural characteristics and the electronic structure. Here, we employed aberration-corrected scanning transmission electron microscopy and spectroscopy to study a NdNiO3/Nd0.8Sr0.2NiO3 bilayer film grown by layer-by-layer molecular beam epitaxy (MBE). In the NNO layer, we found RP faults with multiple configurations, including a 1/2 a <111> shift, single or several intergrowth layers of NNO, and a disappearance of the contrast between Nd and Ni columns in high-angle annular dark-field images. Elemental intermixing occurs at the interface between the SrTiO3 substrate and NdNiO3 as well as in the RP faults region. Quantitative analysis of the variation of lattice constants indicates that large strain exist at the edges of RP faults. We demonstrate that the valence change of Ni ions around RP faults is associated with a strain variation. This work highlights possible effects of RP faults on the microstructure and electronic structure evolution in nickelates.
Title: Low-Dose Electron Crystalloraphy: Strusture Solution and Refinement
Authors: H. Klein; S. Kodjikian
Affiliation: Institut Néel, Université Grenoble Alpes, CNRS, 38000 Grenoble, France
Abstract: There is a wealth of materials that are beam sensitive and only exist in nanometric crystals, because the growth of bigger crystals is either impossible or so complicated that it is not reasonable to spend enough time and resources to grow big crystals before knowing their potential for research or applications. This difficulty is encountered in minerals, zeolites, metal-organic frameworks or molecular crystals, including pharmaceuticals and biological crystals.
In order to study these crystals a structure determination method for beam sensitive crystals of nanometric size is needed. The nanometric size makes them destined for electron diffraction, since electrons interact much more strongly with matter than X-rays or neutrons. In addition, for the same amount of beam damage, electron diffraction yields more information than X-rays.
The recently developed low-dose electron diffraction tomography (LD-EDT) not only combines the advantages inherent in electron diffraction, but is also optimized for minimizing the electron dose used for the data collection. The data quality is high, allowing not only the solution of complex unknown structures, but also their refinement taking into account dynamical diffraction effects.
Here we present several examples of crystals solved and refined by this method. The range of the crystals presented includes a synthetic oxide (Sr5CuGe9O24), a natural mineral (bulachite) and a metal organic framework (Mn-formiate). The dynamical refinement can be successfully performed on data sets that needed less than 0.1 e-/Å² for the entire data set.
Keywords: electron crystallography; beam sensitive materials; structure solution; structure refinement
Title: Two new organic charge transfer co-crystals based on acetamidophenol molecules
Authors: Iryna Andrusenko1; Joseph Hitchen2; Enrico Mugnaioli1; Simon R. Hall2; Mauro Gemmi1
Affiliation: 1Center for Nanotechnology [email protected], Istituto Italiano di Tecnologia, Piazza San Silvestro 12, Pisa 56127, Italy; 2Complex Functional Materials Group, School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UK
Abstract: Herein we present two new organic charge transfer co-crystals obtained through a simple solution growth process and based on an acetamidophenol molecule (either paracetamol or metacetamol), as electron donor, and on 7,7,8,8-tetracyanoquinodimethane (TCNQ), as electron acceptor. Due to the sub-micron size of the crystalline domains, 3D electron diffraction was employed for the structure characterization of both systems. Paracetamol-TCNQ structure was solved by standard direct methods, while the analysis of metacetamol-TCNQ was complicated by the low resolution of the available diffraction data and by the low symmetry of the system. The structure determination of metacetamol-TCNQ was eventually achieved after merging two data sets and employing both direct methods and simulated annealing. Our study reveals that both paracetamol-TCNQ and metacetamol-TCNQ systems crystallize in a 1:1 stoichiometry, assembling in a mixed-stack configuration and adopting an acentric P1 symmetry. It appears that paracetamol and metacetamol do not form a strong structural scaffold based on hydrogen bonding, as previously observed for orthocetamol-TCNQ and orthocetamol-TCNB (1,2,4,5-tetracyanobenzene) co-crystals.
Keywords: electron diffraction, organic charge transfer complex, structure determination, simulated annealing
Title: Two-Dimensional Strain Mapping by Scanning Precession Electron Diffraction: Experimental Set-up and Data Analysis
Authors: Dipanwita Chatterjee1, Ingeborg Nævra Prestholdt1, P. Crout2, Tor Inge Thorsen1, P. A. Midgley2 and Antonius T. J. van Helvoort1
Affiliation: 1 Department of Physics, Høgskoleringen, Norwegian University of Science and Technology, Trondheim, Norway 2 Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS, UK
Abstract: Strain is important for tailoring the properties in functional and engineering materials. For strain analysis with high spatial resolution i.e., beyond that of standard X-ray and scanning electron microscopy-based techniques, transmission electron microscopy (TEM) is required. Several strain measurement techniques are available within the domain of TEM but scanning (precession) electron diffraction (SED/SPED) is generally seen to be one of the most convenient [1,2]. This is because it is an easy technique to set up at the microscope without any special hardware configuration. Once set up, the data acquisition is fast and robust analysis can be automated. S(P)ED based mapping can have both nm scale spatial resolution and a relatively large field of view, as opposed to the measurements made using lattice imaging methods. Precession improves the robustness of the technique and the accuracy of data analysis. In the recent years, two major developments to SED/SPED based techniques have emerged: i) improved electron detection (i.e., the use of the direct electron detectors) and ii) advances in post-processing methodologies. These two factors, together with the electron beam/probe set-up strongly influence the accuracy and precision of strain mapping at the nm-scale. In this contribution, we investigate the influence of these factors on the resulting strain maps. We do this by systematically adjusting (i) the beam/probe configuration (for example, use of probe precession, beam convergence angle), (ii) the detection parameters (for example, pixel size and pixel depth) and (iii) the analysis algorithms (namely, cross-correlation, centre of mass method and Gaussian peak-fitting). A well-characterized GaAs nanowire with a GaAsSb insert has been used as a test object  for this purpose. The data processing has been carried out with the python-based open-source library pyxem  and we include the applied data processing routines. Comparison of the constructed strain maps under varying set-ups shows that the three elements, mentioned above are interdependent. We do however find trends that aid us in identifying the optimum probe settings for achieving accurate strain maps. For all the analyses, the bending of the nanowire sample limits the area that can be investigated. Further, we find that the choice of the reference area is also important. In this work, a best practice routine for strain mapping with S(P)ED including both experimental design and data analysis have been developed and justified. The relevant codes are included to aid replication and further refinement. We have also applied this routine to other materials and specimen geometries including a strain hardened aluminium alloy to verify that its applicability is more generic. The results obtained in the work are insightful and pave the way for more standardized routines with an ultimate goal of developing a convenient and robust three-dimensional strain mapping workflow applicable to a range of functional and engineering materials systems.
Keywords: electron diffraction, organic charge transfer complex, structure determination, simulated annealing
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