It is demonstrated that high‐resolution energy‐dispersive X‐ray fluorescence mapping devices based on a micro‐focused beam are not restricted to high‐speed analyses of element distributions or to the ...detection of different grains, twins and subgrains in crystalline materials but can also be used for the detection of dislocations in high‐quality single crystals. Si single crystals with low dislocation densities were selected as model materials to visualize the position of dislocations by the spatially resolved measurement of Bragg‐peak intensity fluctuations. These originate from the most distorted planes caused by the stress fields of dislocations. The results obtained by this approach are compared with laboratory‐based Lang X‐ray topographs. The presented methodology yields comparable results and it is of particular interest in the field of crystal growth, where fast chemical and microstructural characterization feedback loops are indispensable for short and efficient development times. The beam divergence was reduced via an aperture management system to facilitate the visualization of dislocations for virtually as‐grown, non‐polished and non‐planar samples with a very pronounced surface profile.
A laboratory X‐ray topography technique is presented. One of the advantages of this technique is that it can be used to visualize dislocations in non‐polished and non‐planar crystals with a very pronounced surface profile.
Die Nuklearmedizin ist ein sehr innovatives Fachgebiet und hat sich in den letzten Jahren
durch PET/CT und neue individualisierte Therapien rasant weiterentwickelt. Je komplexer das
Fachgebiet wird, ...desto schwieriger und aufwendiger werden die qualitätssichernden Maßnahmen. Es
ist deshalb wichtig in der Medizin, insbesondere auch in der Nuklearmedizin, stets auf dem
aktuellen Stand des medizinischen Wissens und der Technik zu bleiben.
(K,Na)NbO3 is a lead-free and sustainable ferroelectric material with electromechanical parameters comparable to Pb(Zr,Ti)O3 (PZT) and other lead-based solid solutions. It is therefore a promising ...candidate for caloric cooling and energy harvesting applications. Specifically, the structural transition from the low-temperature Mc- to the high-temperature c-phase displays a rich hierarchical order of domains and superdomains, that forms at specific strain conditions. The relevant length scales are few tens of nanometers for the domain and few micrometers for the superdomain size, respectively. Phase-field calculations show that this hierarchical order adds to the total free energy of the solid. Thus, domains and their formation has a strong impact on the functional properties relevant for electrocaloric cooling or energy harvesting applications. However, monitoring the formation of domains and superdomains is difficult and requires both, high spatial and high temporal resolution of the experiment. Synchrotron-based time-resolved X-ray diffraction methods in combination with scanning imaging X-ray microscopy is applied to resolve the local dynamics of the domain morphology with sub-micrometer spatial and nanosecond temporal resolution. In this regime, the material displays a novel self-stabilization mechanism of the domain morphology, which may be a general property of first-order phase transitions.
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•Dynamics of first order phase transition.•Energy scaling of structural transformation.•Spatial self-stabilization of low-temperature structural phase.
Regarding the undisputed relevance of thermal errors, the question arises in which way the consideration of several activities will lead to an improvement of the thermal behavior of machine tools. ...The answer comes from 75 small to very large machine tool manufacturers and mainly larger production companies from Europe and Asia. Therefore, the entire process chain is considered, from design, assembly to the installation conditions and procedures in daily operations of the machine tool. The companies describe the expenditure regarding the design and the organization to increase the thermoelastic manufacturing accuracy. There are the following remarkable facts. The use of mineral castings is highly dependent on the region. In addition to the thermo-symmetric design, heat removal is an alternative design solution. There are only a few alternatives for tempering. Corrective methods can be very diverse. The consideration of the installation conditions strongly depends on the company size. In addition, the necessary measures in the operation are described by the users, for which purpose they often remain in contact with the manufacturers. Finally, the paper discusses the difficulties regarding the control of thermal behavior from an industrial perspective, deriving future research areas and establishing work priorities.
A novel low-temperature-gradient zone-refining setup is presented here which allows for single crystalline zone-refining of high-purity Ge. The reported single crystalline zone-refined Ge bar has a ...length of 680 mm and shows a high structural quality, as confirmed by X-ray diffraction techniques. The dislocation density determined by an etch pit density analysis lies between 103 and 104 cm−2. The Ge bar has a net charge carrier density down to 4.7⋅1011 cm−3 with a charge carrier mobility of over 3⋅104 cm2V−1s−1 and a charge carrier lifetime of over 50μs. Hence, the crystals produced by this method are comparable to the quality that can be achieved by the Czochralski method, and the exhibited quality is the highest reported quality that has been achieved by zone-refining so far.
•Low-temperature-gradient zone-refining of 680 mm long Ge single crystals.•Zone-refined bars exhibit low dislocation density between 103 to 104 cm−2.•Zone-refined crystals exhibit comparable quality to Czochralski crystals.
Domain configuration in epitaxial antiferroelectric films has been studied by X‐ray nanoscopy, with the extraction of information about the domain sizes beyond the beam‐size limit. The objective of ...this article is to understand how film thickness (the cases of 50 and 1000 nm are explored) and temperature (20 and 200°C) affect the nanodomain configuration of PbZrO3/SrRuO3/SrTiO3 thin films. It is found that the majority of antiferroelectric domains in both films are too small to be directly mappable, because many of them are simultaneously illuminated by the nanobeam (60 × 100 nm) most of the time. Nevertheless, these small sizes can be studied by analysing the diffraction peak width, which is, in the simplest approximation, inversely proportional to the domain size. With this approach it is identified that the characteristic (most probable) domain size does not depend on the film thickness and is ∼13 nm, while the scarcer larger domains do depend on it. An increase of the temperature to 200°C (just below the nominal antiferroelectric‐to‐cubic transition temperature) results in a slight increase in the characteristic size. These results are compared with those in ferroelectric films, where domain sizes are pronouncedly thickness dependent, and the relevant methodological question on the possibility of neglecting the interference of X‐ray waves scattered by different nanodomains in the nanodomain assembly is also discussed.
A new X‐ray based method for studying nanodomain configuration in ferroic materials in the form of thin films is proposed, and its efficiency on classical functional antiferroelectric material PbZrO3 is demonstrated.
The dislocation evolution in a cross-section a-plane cut through a sublimation-grown aluminum nitride (AlN) crystal grown with low-temperature gradients and subsequent low thermal stress is ...investigated with different X-ray diffraction imaging methods. Exploiting the so-called weak-beam contrast using monochromatic X-rays in combination with suitable three-dimensional (3D) interpretation and reconstruction allows the identification of individual dislocations as well as tracing their progression in the crystal volume, even in the considerably strained interface region. It is particularly striking that the laterally grown crystal volume is dislocation-free. The dislocation densities in the seed and the bulk volume are similar (1 × 103 cm–2), but while the dislocations in the seed are randomly arranged, the dislocations in the bulk volume show a uniform line shape, indicating a common mechanism of dislocation movement. Since the dislocation slings in the bulk do not lie in slip planes, it can be concluded that the lateral movement does not result from dislocation glide, but from impurity-driven climb of dislocations during growth. The absence of slip can be explained by the low-temperature gradients and the subsequent low thermal stress below the critical resolved shear stress (CRSS).
Domain configuration in epitaxial antiferroelectric films has been studied by X-ray nanoscopy, with the extraction of information about the domain sizes beyond the beam-size limit. The objective of ...this article is to understand how film thickness (the cases of 50 and 1000 nm are explored) and temperature (20 and 200°C) affect the nanodomain configuration of PbZrO
3
/SrRuO
3
/SrTiO
3
thin films. It is found that the majority of antiferroelectric domains in both films are too small to be directly mappable, because many of them are simultaneously illuminated by the nanobeam (60 × 100 nm) most of the time. Nevertheless, these small sizes can be studied by analysing the diffraction peak width, which is, in the simplest approximation, inversely proportional to the domain size. With this approach it is identified that the characteristic (most probable) domain size does not depend on the film thickness and is ∼13 nm, while the scarcer larger domains do depend on it. An increase of the temperature to 200°C (just below the nominal antiferroelectric-to-cubic transition temperature) results in a slight increase in the characteristic size. These results are compared with those in ferroelectric films, where domain sizes are pronouncedly thickness dependent, and the relevant methodological question on the possibility of neglecting the interference of X-ray waves scattered by different nanodomains in the nanodomain assembly is also discussed.
Paracoccus pantotrophus cytochromecd1 is an enzyme of bacterial respiration, capable of using nitrite in vivo and also hydroxylamine and oxygen in vitro as electron acceptors. We present a ...comprehensive analysis of the steady state kinetic properties of the enzyme with each electron acceptor and three electron donors, pseudoazurin and cytochrome c550, both physiological, and the non-physiological horse heart cytochromec. At pH 5.8, optimal for nitrite reduction, the enzyme has a turnover number up to 121 s−1 perd1 heme, significantly higher than previously observed for any cytochrome cd1. Pre-activation of the enzyme via reduction is necessary to establish full catalytic competence with any of the electron donor proteins. There is no significant kinetic distinction between the alternative physiological electron donors in any respect, providing support for the concept of pseudospecificity, in which proteins with substantially different tertiary structures can transfer electrons to the same acceptor. A low level hydroxylamine disproportionase activity that may be an intrinsic property of cytochromes c is also reported. Important implications for the enzymology of P. pantotrophuscytochrome cd1 are discussed and proposals are made about the mechanism of reduction of nitrite, based on new observations placed in the context of recent rapid reaction studies.
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