Vibrational study of A3In2B"O9 (A=Ba, Sr; B" = U, W) double perovskites

E. N. SILVA, A. P. AYALA. GUEDES, S. A. LARREGOLA, R. M. PINACCA, M. DEL C. VIOLA AND J. C. PEDREGOSA

JOURNAL OF RAMAN SPECTROSCOPY

Wiley Interscience

Año: 2009 p. 1028 - 1032

0377-0486

Raman scattering and infrared transmittance techniques were used to investigate the room-temperature phonon spectra of the polycrystalline Ba3In2UO9, Sr3In2UO9, Ba3In2WO9 and Sr3In2WO9 double perovskites. Although X-ray diffraction has shown that both Ba3In2UO9 and Ba3In2WO9 crystallize in a disordered cubic (Pm3m−Oh) structure with one formula unit per unit cell (Z = 1), Raman measurements revealed that both Ba3In2UO9 and Ba3In2WO9 compounds should exhibit a 1 : 1 ordered domains with Fm3m symmetry, embedded in the Pm3m matrix. Observation of a í1 like vibration of the InO6 octahedron reflects the occurrence of a two-phonon-like behavior due to the intrinsic occupational disorder at octahedral symmetry sites. Assignment of most of the Raman and infrared phonons is also given.