Synthese und in-situ Untersuchungen dreidimensionaler Silicium- und Germaniumnetzwerke unter Druck

Schwerpunkte der Arbeit waren die Synthese und in-situ Charakterisierung metastabiler Modifikationen der Elemente Silicium und Germanium, sowie die Darstellung binärer Silicide und Germanide der Erdalkali- und Seltenerdmetalle unter Druck (bis 20 GPa) und bei hoher Temperatur (bis 2200 K). Dabei konnten die Phasenbeziehungen von Allotropen des Germaniums näher beleuchtet werden und es gelang, eine neue Germaniummodifikation, Ge(hR8), in-situ strukturell zu charakterisieren. Die neu dargestellten metastabilen binären Silicide und Germanide unterteilen sich strukturell in solche, die clathratartige Tetrel-Netzwerke mit einer Koordinationszahl von drei und vier enthalten und in jene, bei denen die Anzahl benachbarter Tetrelatome vier übersteigt. So konnten beispielsweise Netzwerke dargestellt werden, die acht homonukleare Silicium oder Germanium Kontakte im Netzwerk aufweisen. Neben der strukturellen Charakterisierung standen die Bestimmungen der elektrischen Leitfähigkeit und des Magnetismus, sowie die Ermittlung der thermischen Eigenschaften im Focus der Arbeit.Key aspects of the present work were the synthesis and in-situ characterization of metastable modifications of elemental silicon and germanium as well as the preparation of binary silicides and germanides of the alkaline earth and rare earth metals under pressure (up to 20 GPa) and at elevated temperatures (up to 2200 K). In that process the phase relations of germanium allotropes could be examined more closely and led to the preparation of a new germanium modification, Ge(hR8), which could be structurally characterized by in-situ experiments. The prepared silicides and germanides can be structurally separated in those containing clathrate-like networks with a coordination number of three and four and those which contain more neighbors in the network than four e.g., eight homonuclear silicon or germanium contacts in the network of CeSi5 and CeGe5. Beside the structural characterization the determination of the electrical resistivity and the magnetical properties as well as the analysis of the thermal behavior were in focus of the work

Crystal Growth and Structure Determination of Pigment Orange 82

The crystal structure of the important industrial orangepigment PO82, major part of the BASF Colors amp; Effects productSicopal Orange K L 2430, was solved from combined X ray singlecrystal, X ray and neutron powder diffraction,119Sn Mössbauer spec troscopy, transmission electron microscopy, electron diffraction, andchemical analyses. The structure contains Keggin type clusters com posed of four [M3O13] trimers consisting each of three MO6 octahedra that share edges and one common oxygen atom connecting the trimersto the central ZnO4tetrahedron. The octahedrally coordinated metalatom position is mixed occupied by Ti4 ,Sn4 , and Zn2 . AdjacentKeggin clusters share vertices and are further interconnected to fourZnO4tetrahedra. This framework of interconnectedMO6octahedra andZnO4tetrahedra contains channels along [110], in which the Sn2 cat ions are locate

Оценка чувствительности термомагнитометрического метода определения магнитных фвз

Объектом исследования является литий-замещенные ферриты Цель работы: определение чувствительности термомагнитометрического метода оценки фазового состава магнитных материалов. Определение минимального содержания магнитной фазы в феррите, при котором можно исследовать образец термомагнитометрическим методом. Методология проведения исследования и аппаратура: измерение термогравиметрических кривых (ТГ/ДТГ) ферритовых образцов проводилось на термическом анализаторе STA 449C Jupiter (Netzsch, Германия) с приложенным магнитным полем. Определение фазового состава с использованием дифрактометра ARL X’TRA.The object of research is the lithium-substituted ferrites Objective: To determine the sensitivity of the termomagnitometry method assessment phase structure of magnetic materials. Determination of the minimum content of the magnetic ferrite phase, in which the sample can be examined by termomagnitometry method. The methodology of the research and instruments: measurement of thermogravimetric curve (TG / DTG) ferrite samples was carried out on the thermal analyzer STA 449C Jupiter (Netzsch, Germany) with an applied magnetic field. Determination of the phase composition using a diffractometer ARL X'TRA

Origin of Pressure-Induced Metallization in Cu3N: An X-ray Absorption Spectroscopy Study

The authors are grateful to Professor Alain Polian for providing the NDAC cell.High-pressure (0–26.7 GPa) Cu K-edge X-ray absorption spectroscopy is used to study possible structural modifications of anti-perovskite-type copper nitride (Cu3N) crystal lattice. The analysis of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), based on theoretical full-multiple-scattering and single-scattering approaches, respectively, suggests that at all pressures the local atomic structure of Cu3N remains close to that in cubic (Formula presented.) phase. Therefore, the transition to metal state above 5 GPa, observed previously using pressure-dependent electrical resistance and optical absorption measurements, is explained by the band gap collapse due to a decrease of the unit cell volume. We found that the lattice parameter of Cu3N is reduced by ≈2% upon increasing pressure up to 26.7 GPa, and the structure is restored upon pressure release.This study was supported by Latvian National Research program IMIS2. The experiment at the SOLEIL synchrotron radiation facility received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) CALIPSO under Grant agreement no. 312284; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART