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SUMMARY:Dislocation-Based Functionality in Oxides - Prof. Dr. Jürgen Röd
 el\, Department of Materials and Earth Sciences\, TU Darmstadt
DTSTART:20191122T150000Z
DTEND:20191122T160000Z
UID:TALK126484@talks.cam.ac.uk
CONTACT:Yonatan Calahorra
DESCRIPTION:While my group in the last 14 years worked mostly on lead-free
  piezoceramics\, this topic has matured considerably and we now mostly wor
 k with industry to transfer knowledge into application. Our new topic with
  currently four researchers and four openings centers on dislocation-based
  functionality: \nDislocations in oxides are typically heavily charged and
  embedded in a shell of compensating space charges. Therefore they provide
  a linear or two-dimensional array of charges stable up to high temperatur
 e without any chemical dopant. In the literature dislocations have been de
 monstrated to enhance oxygen conductivity and to improve the figure of mer
 it of thermoelectrics by reducing thermal conductivity through phonon scat
 tering by dislocations. Dislocations have been suggested to improve interf
 acial reaction kinetics and have been theoretically predicted to pin domai
 n walls in ferroelectrics. \nIn Darmstadt we have so far focused on establ
 ishing a set of techniques to introduce a high density of bulk dislocation
 s into single crystals at room temperature or enhanced temperature and to 
 study (dislocation) creep in polycrystalline oxides. Structural investigat
 ions have been performed by dark-field X-ray diffraction\, rocking curve a
 nalysis\, TEM\, PFM\, NMR and etching techniques. The first property evalu
 ations have been done with respect to electrical and thermal conductivity 
 and domain wall pinning. \nSelect examples will be provided on dislocation
  structures\, electrical and thermal conductivity. We have been working on
  SrTiO3\, BaTiO3\, KNbO3\, TiO2 and ZrO2.
LOCATION:Goldsmiths 1\, Lecture Theatre\, Department of Materials Science 
 &amp\; Metallurgy
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