Ferroelectric Phase Transitions in BaTiO3 Studied by DAFS

Abstract

Bruce Ravel
Ceramic Division Film
Characterization and Properties Group

 

BaTiO3 undergoes three structural and ferroelectric phase transitions between 183K and 393K. It has been shown that the symmetry properties of the local structure in this material as measured by X-ray Absorption Fine Structure spectroscopy (XAFS) differ from the symmetry of the crystallographic structure throughout this sequence of phase transitions. Unfortunately, a fully quantitative analysis of the Ti K edge XAFS in BaTiO3 is hindered by the proximity in energy of the barium LIII edge, which severely limits the information content of titanium XAFS signal.

I have applied Diffraction Anomalous Fine Structure spectroscopy (DAFS) to BaTiO3 to resolve this problem. DAFS combines the crystallographic sensitivity of x-ray diffraction with the local spatial resolution of XAFS. With these DAFS spectra, the fine structure contributions of the titanium and barium absorbers are separable, even in the overlapping energy region. By analyzing the separated titanium spectrum, I can more fully understand the local structure of this important material and its relationship to ferroelectricity throughout its phase transitions.

In this poster, I present the results of initial measurements of the BaTiO3 DAFS at several temperatures, discuss the analasis of these data, and consider future applications of this novel use of DAFS.

 

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Bruce Ravel

Last modified: Wed Feb 18 15:56:11 EST 1998