Infrared and Raman spectroscopy investigations in mullite-type Bi2(FexGa1-x)4O9 polycrystals.

Mullite-type Bi2(FexGa1-x)4O9 (0 ≤ x ≤ 1) oxides, prepared by mecanochemical-thermal synthesis, were investigated by FTIR and Raman spectroscopies. Similarly to other mullite systems, IR (850–400 cm−1) and Raman bands (750–300 cm−1) are attributed to stretching and bending vibrations of tetrahedral and octahedral sites. A shift in the peak positions toward lower wavenumbers with the increase of iron content is observed. High-energy IR modes show only the presence of Ga-O-Ga and Ga-O-Fe/Fe-O-Ga stretching vibrations for x < 0.5. Raman bands between 500 cm−1 and 400 cm−1 revealed double band splitting for x < 0.5. [ABSTRACT FROM AUTHOR]