Final Report

J. Toulouse

关键词: ACOUSTICS;    NEUTRONS;    PERMITTIVITY;    PHONONS;    SCATTERING ferroelectrics;    relaxors;    phase transition;    dielectric;    neutron scattering;    Raman scattering;   

DOI  :  10.2172/1037877
RP-ID  :  DOE/ER/46318-7
PID  :  OSTI ID: 1037877
Others  :  TRN: US1201774

美国|英语

来源: SciTech Connect

【 摘 要 】

The purpose of this project was to better understand the 'Multiscale Dynamics of Relaxor Ferroelectrics'. The output of the project is summarized in the narrative. The results of the work were presented at a number of different conferences and four papers were written, the references to which are also indicated in the report and which have also been uploaded on e-link. The multiscale dynamics of relaxors was clearly identified in the three characteristic temperatures that were identified. In particular, we were the first group to identify an intermediate temperature, T*, at which the correlations between off-center ions in relaxor cross-over from being dynamic to being static and giving rise to the characteristic relaxor behavior in the dielectric constant. Other groups have now confirmed the existence of such an intermediate temperature. We also made and reported two other observations: (1) a coherent interference phenomena (EIT-like effect) near the transition of several relaxors, which provides information on the nature and mechanism of the transition; and (2) in a similar way, inelastic neutron scattering results were interpreted as resonant scattering of acoustic phonons by localized modes in polar nanodomains. In parallel with the neutron scattering work, we also developed a theory of the scattering of phonons by the above localized modes. The theoretical development is very formal at this point and did not allow an easy comparison with the experimental results. This work is in progress.