Tung-Ching Huang et al 2007 J. Phys.: Condens. Matter 19 476212 doi:10.1088/0953-8984/19/47/476212
Tung-Ching Huang1, Mei-Tan Wang1, Hwo-Shuenn Sheu2 and Wen-Feng Hsieh1,3
Show affiliationsBy applying a single-tetragonal-phase model to refine the crystal structure and the coupled-phonon model to analyze transverse optical (TO) modes of BaTiO3 nanocrystals, we found, upon decreasing the particle size from 140 to 30 nm, that the tetragonality of BaTiO3 nanocrystallites is reduced accompanied by expanding unit-cell volume, which is the dominant mechanism for reducing giant LO–TO splitting in the BaTiO3 system. The weakening coupling of two low-frequency modes among three A1 (TO) phonons leads to changing the lowest one from a spectral dip to a peak, whereas the increasing coupling strength between two high-frequency modes repels them farther so that there is less reduction in spectral separation.
77.84.Dy Niobates, titanates, tantalates, PZT ceramics, etc.
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
Issue 47 (28 November 2007)
Received 10 August 2007, in final form 5 October 2007
Published 1 November 2007
Tung-Ching Huang et al 2007 J. Phys.: Condens. Matter 19 476212
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