Structural Evolution of BaTiO[subscript 3] Nanocrystals Synthesized at Room Temperature

Journal Article · Wed Jul 11 04:00:00 EDT 2012 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja303184w· OSTI ID:1043720

Rabuffetti, Federico A; Brutchey, Richard L ^[1]

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1. USC

Sub-10 nm BaTiO{sub 3} nanocrystals were synthesized at room temperature via the vapor diffusion sol-gel method, and their structural evolution during nucleation and growth stages was followed using a series of techniques that probe the atomic structure on different length and time scales. Special emphasis was placed on assessing the evolution of the local symmetry and structural coherence of the resulting nanocrystals, as these are the structural bases for cooperative properties such as ferroelectricity. Although the room-temperature crystal structure of the fully grown nanocrystals appears cubic to Rietveld analysis of synchrotron X-ray diffraction data, Raman spectroscopy and pair distribution function analysis demonstrate the presence of non-centrosymmetric regions arising from the off-centering of the titanium atoms. This finding demonstrates that accounting for diffuse scattering is critical when attempting the structural characterization of nanocrystals with X-ray diffraction. The local symmetry of acentric regions present in BaTiO{sub 3} nanocrystals, particularly structural correlations within an individual unit cell and between two adjacent unit cells, is best described by a tetragonal P4mm space group. The orthorhombic Amm2 space group also provides an adequate description, suggesting both types of local symmetry can coexist at room temperature. The average magnitude of the local off-center displacements of the titanium atoms along the polar axis is comparable to that observed in bulk BaTiO{sub 3}, and their coherence length is on the order of 16 {angstrom}. The presence of local dipoles suggests that a large amount of macroscopic polarization can be achieved in nanocrystalline BaTiO{sub 3} if the coherence of their ferroelectric coupling is further increased.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: UNIVERSITYDOE - BASIC ENERGY SCIENCES
• OSTI ID: 1043720
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 22 Vol. 134; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ATOMS
COHERENCE LENGTH
CRYSTAL STRUCTURE
DIFFUSE SCATTERING
DIFFUSION
DIPOLES
DISTRIBUTION FUNCTIONS
NUCLEATION
POLARIZATION
PROBES
RAMAN SPECTROSCOPY
SPACE GROUPS
SYMMETRY
SYNCHROTRONS
TITANIUM
X-RAY DIFFRACTION