Controlled synthesis of photoluminescent Bi4Ti3O12 nanoparticles from metal-organic polymeric precursor

Bi4Ti3O12 (BIT) nanoparticles with a narrow average particle size distribution in the range of 11-46 nm was synthesized via a metal-organic polymeric precursor process. The crystallite size and lattice parameter of BIT were determined by XRD analysis. At annealing temperatures >550 degrees C, the orthorhombic BIT compound with lattice parameters a = 5.4489 angstrom, b = 5.4147 angstrom, and c = 32.8362 angstrom was formed while at lower annealing temperatures orthorhombicity was absent. Reaction proceeded via the formation of an intermediate phase at 500 degrees C with a stoichiometry close to Bi2Ti2O7. The particle size and the agglomerates of the primary particles have been confirmed by FESEM and TEM. The decomposition of the polymeric gel was ascertained in order to evaluate the crystallization process from TG-DSC analysis. Raman spectroscopy was used to investigate the lattice dynamics in BIT nanoparticles. In addition, investigation of the dependence of the visible emission band around the blue-green color emission on annealing temperatures and grain sizes showed that the effect of grain size plays important roles, and that oxygen vacancies may act as the radiative centers responsible for the observed visible emission band.