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Crystal structures and phonon modes of Ba(Ca 1/2 W 1/2 )O 3 , Ba(Ca 1/2 Mo 1/2 )O 3 and Ba(Sr 1/2 W 1/2 )O 3 complex perovskites investigated by Raman scattering
Author(s) -
Dias Anderson,
Siqueira Kisla P. F.,
Moreira Roberto L.
Publication year - 2010
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.2399
Subject(s) - raman spectroscopy , triclinic crystal system , monoclinic crystal system , crystallography , crystal structure , phonon , materials science , analytical chemistry (journal) , chemistry , physics , condensed matter physics , optics , chromatography
This work investigates the crystal structures and phonon modes of Ba(Ca 1/2 W 1/2 )O 3 , Ba(Ca 1/2 Mo 1/2 )O 3 and Ba(Sr 1/2 W 1/2 )O 3 perovskites by Raman spectroscopy. The samples were produced by conventional solid‐state processing at 1200 °C. X‐ray diffraction showed that single‐phase homogeneous materials were produced, which are cubic or pseudo‐cubic in symmetry. The existing controversies in the literature for these complex perovskites were investigated by comparing experimental Raman data with group‐theory analysis. Ceramics with Ca and W or Mo were found to be cubic, space group Fm 3 m . For these materials, four Raman‐active bands were observed and the fitting parameters showed that the Ba(Ca 1/2 Mo 1/2 )O 3 ceramic presents bands at lower wavenumbers if compared with the Ba(Ca 1/2 W 1/2 )O 3 sample. For the Ba(Sr 1/2 W 1/2 )O 3 material, two hypotheses were investigated for monoclinic or triclinic structures. The experimental results showed 12 Raman‐active modes for this ceramic, which is in perfect agreement with the theoretical predictions for a monoclinic ( I 2/ m ) structure. Copyright © 2009 John Wiley & Sons, Ltd.