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Raman scattering studies on nanocrystalline BaTiO 3 Part II—consolidated polycrystalline ceramics
Author(s) -
Shiratori Y.,
Pithan C.,
Dornseiffer J.,
Waser R.
Publication year - 2007
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1763
Subject(s) - raman spectroscopy , materials science , ceramic , crystallite , tetragonal crystal system , nanocrystalline material , phonon , grain size , curie temperature , phase transition , analytical chemistry (journal) , raman scattering , phase (matter) , mineralogy , condensed matter physics , composite material , nanotechnology , optics , metallurgy , chemistry , ferromagnetism , physics , organic chemistry , chromatography
BaTiO 3 dense ceramics with different grain sizes from 5.6 µm down to 35 nm were thoroughly studied by Raman spectroscopy. The temperature characteristics of optical phonons were compared with those obtained for powders. The micrograined ceramic revealed the well‐known spectrum profiles and transitions, typical for bulk BaTiO 3 . On the other hand, the Raman spectra obtained for a nanograined ceramic with an average grain size of 35 nm revealed a tetragonally distorted pure BaTiO 3 phase showing a diffused phase transition behaviour with respect to temperature. Abnormality of phonon damping characteristics for the nanograined ceramic was demonstrated through comparison with powders with various crystallite sizes and the micrograined ceramic. The Curie temperature of the nanograined ceramic was estimated to be 105 °C from the temperature characteristic of a sharp peak at 307 cm −1 , which is one of the most specific tetragonal features for bulk BaTiO 3 . In the present study, local stabilization of the tetragonal phase in ultra‐fine grains was experimentally demonstrated from comparison between the Raman spectroscopic results for powders and ceramics prepared through microemulsion‐mediated synthesis. Rather long phonon mean free paths can exist even in such ultra‐fine grains, but the phonon characteristics originating from various grains are diffused mainly because of the effect of internal stress. Copyright © 2007 John Wiley & Sons, Ltd.