Prof. Dr. S. Kapphan Doktoranden :
Dipl.-Phys. J. Licher, Dipl.-Phys. M. Gao Die Mischkristall der beiden incipient ferroelektrischen Systeme KTaO3 und SrTiO3 weisen zum Teil neue und überraschende Eigenschaften auf die auch die Störstellen in diesen Systemen betreffen.
Die hohe Polarisierbarkeit dieser Quantenparaelektrika bei tiefen Temperaturen führt zu polaren glasähnlichen Phasenübergängen und kooperativen Beweglichkeiten von Elektronen- und Lochpolaronen und dipolaren resonanten Relaxationserscheinungen in dielektrischen Messungen.
www.physik.uni-osnabrueck.deThe open tungsten bronze structure of SBN allows various possibilities to accommodate different doping ions, taking into account structurally open sites and, additionally, that only five of six available positions of Sr2 + and Ba2 + host cations are occupied.
Instrumental neutron activation analysis shows that Ce3+ ions occupy Sr2+/Ba2+ sites and Cr3+ ions substitute Nb5+ ions 16,17, but the charge compensation mechanism has not yet been determined.
Doping by Ce or Cr shifts the ferroelectric phase transition temperature Tc (4/mmm ® 4mm) from ~ 253 K in pure congruent SBN to lower temperatures inversely proportionally to the doping concentration 18,19. Co-doping effects, simultaneously by Ce and Cr, have not been investigated so far and this report present the first information in this regard.
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