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Der Einfluss von Defekten auf das Schaltverhalten ferroelektrisch modulierter Substanzen

dc.contributor.advisorEckold, Götz Prof. Dr.
dc.contributor.authorBehrendt, Karsten
dc.publisherNiedersächsische Staats- und Universitätsbibliothek Göttingende
dc.titleDer Einfluss von Defekten auf das Schaltverhalten ferroelektrisch modulierter Substanzende
dc.title.translatedThe influence of defects on the switching behaviour of ferroelectric modulated substancesde
dc.contributor.refereeEckold, Götz Prof. Dr.
dc.description.abstractengThe influence of defects on the phase transition behavior of A2BX4-compounds was studied by diffraction methods, impedance spectroscopy and atomic force microscopy. It was found that chemical point defects have a strong effect on the transition kinetics, whereas the thermodynamic stability of different modulated phases is only slightly affected by such doping with alkali ions. The lock-in-transition from incommensurate to commensurate modulated is slowed down by several orders of magnitude. The transition time hereby ranges from minutes to months, depending on impurity concentration. Due to this, metastable incommensurate phases can be obtained at room temperature. These undercooled phases exhibit remarkable structural and dielectric properties, such as polar nanodomains. The metastable phases undergo additional phase transitions into newly discovered commensurate phases. A unique property of those phases is a memory effect, which allows the incommensurate phase to be re-formed upon subsequent heating. A detailed microscopic model is discussed, which describes all aspects of the observed behavior. This model is based on the formation of a defect density wave and considers its interaction with discommensurations in the incommensurate phase. The thermodynamic properties of all observed phases can be deduced from this
dc.contributor.coRefereeStalke, Dietmar Prof. Dr.
dc.contributor.thirdRefereeMata, Ricardo Prof. Dr.
dc.contributor.thirdRefereeVana, Philipp Prof. Dr.
dc.contributor.thirdRefereeZeuch, Thomas Dr.
dc.contributor.thirdRefereeMeyer, Franc Prof. Dr.
dc.subject.engphase transitionde
dc.subject.engatomic force microscopyde
dc.subject.engimpedance spectroscopyde
dc.subject.engmetastable phasesde
dc.affiliation.instituteFakultät für Chemiede
dc.subject.gokfullChemie  (PPN62138352X)de

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