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Optical and structral properties of pure and Ce-doped nanocrystals of barium titanate
Authors:Ming-Sheng Zhang   Jian Yu   Wan-chun Chen  Zhen Yin
Affiliation:

a Center for Materials Analysis and National Laboratory of Solid State Microstructures Nanjing University, Nanjing 210093, P. R., China

b National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics Chinese Academy of Sciences, Shanghai 200083, P.R. China

c Institute ofPhysics, SinicaAcademia, Bejiing 100080, P. R., China

Abstract:Nanocrystals barium titanate (nc-BT) and Ce-doped barium titanate were synthesized by an unusual hydrothermal process. X-ray diffraction and Raman spectroscopy were used to investigate their microstructures, as well as their lattice vibration and photoluminescence (PL) spectra. Particle sizes as small as 20 nm were measured by X-ray diffraction pattern via Scherer equation. The critical size relative to the cubic-tetragonal transition is about 48 nm in nc-BT below which ferroelectricity vanishes. The lattice parameter ratio c/a of is equal to 1.003, much smaller than 1.01 for that of the bulk crystal, leading to a weakening of ferroelectricity. Hydroxyl defects are observed in the Ce-doped nc-BT samples which show a vibrational band at 3300 em t. Good crystallization character and the lattice perfection were characterized by Raman spectra in the nanophase barium titanate. Strong PL spectra centered at 696 and 585 nm were observed in the pure and Ce-doped nc-BT, respectively. PL dependence on temperature and annealing time was examined. A molecule-like recombination and the charge transfer between Ce4+ and Ce 3+ are proposed to elucidate the luminescence process in the nc-BT and Cc-doped nc-BT system.
Keywords:Photoluminescence   Microstructure   Nanocrystal   Barium Titanate:Ce
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