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Characterization of phase transitions by the analysis of crystal structures

URN to cite this document: urn:nbn:de:bvb:703-opus-6515

Title data

Angelkort, Joachim:
Characterization of phase transitions by the analysis of crystal structures.
Bayreuth , 2009
( Doctoral thesis, 2009 , University of Bayreuth, Faculty of Mathematics, Physics and Computer Sciences)

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Abstract

In this thesis results of the investigations of the mechanisms of solid-solid phase transitions are reported on basis of the exemplary characterization of the phase transition of the metalorganic compound Eu(SC36H49)2 and of the inorganic transition-metal compounds TiI3 and CrOCl. The phase transitions were surveyed temperature dependently by the performance of single-crystal X-ray diffraction experiments and measurements of the magnetic susceptibility. The X-ray diffraction experiments were carried out as data collections of integrated intensities of reflections and as measurements of profiles on selected reflections in so-called omega-2theta maps. The data sets of the integrated intensities were used to determine the crystal structures at different temperatures. By the comparison of the high- and the low-temperature crystal structures the mechanisms of the phase transitions of the compounds Eu(SC36H49)2 and TiI3 were determined. Furthermore the transition temperatures of all three compounds were determined by temperature-dependent measurements of intensities of superstructure reflections. From the omega-2theta maps the monoclinic lattice distortion of the low-temperature phase of CrOCl was determined.

Abstract in another language

Thema der vorliegenden Dissertation ist die Untersuchung von Mechanismen von fest-fest Phasenübergängen, welche anhand des Phasenübergangs der Organometallverbindung Eu(SC36H49)2 und der anorganischen Übergangsmetallverbindungen TiI3 und CrOCl dargelegt werden. Die Phasenübergänge wurden in Abhängigkeit von der Temperatur mittels Einkristallröntgenbeugung sowie Messungen der magnetischen Suszeptibilität untersucht. Bei den Röntgenbeugungsexperimenten handelte es sich um Messungen von integrierten Reflexintensitäten und Messungen von Reflexprofilen in so genannten omega-2theta-Maps. Die Datensätze der integrierten Reflexintensitäten wurden dazu verwendet, Kristallstrukturen bei unterschiedlichen Kristalltemperaturen zu bestimmen. Durch das Vergleichen der Hoch- und Tieftemperaturstrukturen wurden die Mechanismen der Phasenübergänge der Verbindungen Eu(SC36H49)2 und TiI3 bestimmt. Darüberhinaus wurden durch temperaturabhängige Intensitätsmessungen an Überstrukturreflexen die Übergangstemperaturen der fest-fest Übergänge aller drei untersuchten Verbindungen ermittelt. Aus den omega-2theta-Maps wurde die monokline Gitterverzerrung von CrOCl in der Tieftemperaturphase bestimmt.

Further data

Item Type: Doctoral thesis (No information)
Keywords: Phasenumwandlung; Strukturelle Phasenumwandlung; Übergangsmetallverbindungen; Kristallstruktur; Strukturverfeinerung; Ordnungs-Unordnungs-Umwandlung; Phase transition; crystal structure; structure refinement; transition-metal compounds; crystal twinning
DDC Subjects: 500 Science > 530 Physics
Institutions of the University: Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences > Chair Crystallography > Chair Crystallography - Univ.-Prof. Dr. Sander van Smaalen
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences
Faculties > Faculty of Mathematics, Physics und Computer Science > Group Material Sciences > Chair Crystallography
Language: English
Originates at UBT: Yes
URN: urn:nbn:de:bvb:703-opus-6515
Date Deposited: 25 Apr 2014 10:06
Last Modified: 01 Feb 2016 11:48
URI: https://epub.uni-bayreuth.de/id/eprint/476

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