Structure evolution and dielectric behavior of polystyrene-capped barium titanate nanoparticles

作者：Guo H Z; Mudryk Ya; Ahmad M I; Pang X C; Zhao L; Akinc M; Pecharsky V K; Bowler N; Lin Z Q; Tan X^*

来源：Journal of Materials Chemistry, 2012, 22(45): 23944-23951.

DOI：10.1039/c2jm35600g

Polystyrene-capped barium titanate (BaTiO3) nanoparticles with sizes of 11 nm and 27 nm were prepared using amphiphilic star-like diblock copolymer templates. The crystal structure evolution of these nanoparticles over a wide temperature range (10-428 K) was investigated by powder X-ray diffraction. The Rietveld refinement indicates that the abrupt structural transitions observed in micron-sized powders become broad as the particle size is reduced to a few tens of nanometers. The orthorhombic phase (Amm2) is observed in the range of 10-388 K, coexisting with the rhombohedral phase (R3c) at lower temperatures and with the tetragonal phase (P4mm) at higher temperatures. At room temperature (300 K), polystyrene-capped BaTiO3 nanoparticles, both 11 and 27 nm sizes, primarily adopt the tetragonal phase, transforming to the cubic phase (Pm (3) over barm) at 398 K during heating. The phase evolution of the nanoparticles correlates well with their dielectric behavior. With the Landauer-Bruggeman effective approximation, the dielectric properties at room temperature of the BaTiO3 core were calculated and the results are in agreement with the size effect of BaTiO3 nanocrystals.

• 出版日期2012-12-7