Structural disorder in perovskite ferroelectric crystals as revealed by XAFS

Edward A. Stern, Yizhak Yacoby

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

The question whether ferroelectrics of the perovskite structure are driven by displacive or order-disorder mechanisms has been decided currently in favor of displacive based primarily on their dynamic behavior, particularly the existence of a soft mode both below and above Tc. However, various recent experiments have suggested that perovskite ferroelectrics and other ferroelectric crystals, are, in fact, disordered above Tc, contrary to the displacive mechanism. Recent developments in X-ray Absorption Fine Structure (XAFS) analysis have facilitated detailed investigation of the temperature dependence of the local structure providing, for the first time, a direct quantitative way to investigate the form of the local potential energy and the extent of disorder in both pure and mixed ferroelectrics as well as pure and mixed antiferrodistortive crystals. The surprising result is that in all the crystals studied so far, the low temperature local distortions remain large well above Tc. The macroscopic distortions vary by essentially disordering these local distortions and not by their decrease, indicating that the phase transition driving mechanism has a significant order-disorder component.

Original languageEnglish
Pages (from-to)1449-1455
Number of pages7
JournalJournal of Physics and Chemistry of Solids
Volume57
Issue number10
DOIs
StatePublished - Oct 1996
Externally publishedYes

Bibliographical note

Funding Information:
DOE Grant No.DE-FGO6-90ER4542a5n d BSF Grant No. 92-0034B8.e amlineX l 1-A at NSLS whereth eX AFS measuremenwtse rem adei s supportedb y DOE Grant No. DE-FGO5-89ER4538W4e. gratefullayc knowledgthee commenotsf ProfsB . Spivaka ndS . Ghose.

Keywords

  • A. inorganic compounds
  • A. oxides
  • C. XAFS
  • D. ferroelectricity
  • D. phase transitions

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