Lattice vibration of bismuth titanate nanocrystals prepared by metalorganic decomposition

Bismuth titanate (Bi4Ti3O12 (BTO)) nanocrystals have been prepared by metal–organic decomposition. X-ray diffraction revealed that the BTO nanocrystals belong to the orthorhombic system with average size of ∼60 nm. Raman scattering and Fourier-Transform infrared measurements of BTO nanocrystals showed a large decrease of the number of peaks comparing to the space group theoretical analysis. It could be interpreted by the fact that the characteristic vibration modes of BTO nanocrystals arise mainly from the internal modes of TiO6 octahedra, which in return lead to modes degeneration. Raman shifts and infrared absorption bands of BTO nanocrystals were tentatively assigned. Large distortions in Ti(2)O6 octahedra lead originally Raman active modes to become IR active as well and are testified by our FTIR result. An inactive mode for has been found in both our Raman and FTIR data. That might be originated from oxygen vacancies and internal strain, which is commonly explained for the mechanism of the fatigue in BTO.