Structural Explanation of the Dielectric Enhancement of Barium Titanate Nanoparticles Grown under Hydrothermal Conditions

Abstract

When synthesized under certain conditions, barium titanate (BaTiO 3 , BTO) nanoparticles are found to have the non-thermodynamic cubic structure at room temperature. These particles also have a several-fold enhanced dielectric constant, sometimes exceeding 6000, and are widely used in thin-layer capacitors. A hydrothermal approach is used to synthesize BTO nanocrystals, which are characterized by a range of methods, including X-ray Rietveld refinement and the Williamson-Hall approach, revealing the presence of significant inhomogeneous strain associated with the cubic phase. However, X-ray pair distribution function measurements clearly show the local structure is lower symmetry than cubic. This apparent inconsistency is resolved by examining 3D Bragg coherent diffraction images of selected nanocrystals, which show the existence of ≈50 nm-sized domains, which are interpreted as tetragonal twins, and yet cause the average crystalline structure to appear cubic. The ability of these twin boundaries to migrate under the influence of electric fields explains the dielectric anomaly for the nanocrystalline phase.

Biophysical stimulation for bone regeneration using a chitosan/barium titanate ferroelectric composite

“…2 The band observed at lower wavenumbers is one of the ‘fingerprints’ of barium titanate and it is attributed to the Ba–O and Ti–O metal oxide vibration. 2,33 In the case of composites with BT nanoparticles (Fig. 3), the Ti–O I stretching band shift at a higher value of the wavenumber is very important because it suggests the formation of BaTiO 3 tetragonal phase thus confirming the X-ray diffraction analysis.…”

Ferroelectric Texture of Individual Barium Titanate Nanocrystals

“…36 We examined our BTO NC edge with HR-STEM (Figure S2) but could not detect a layer of different symmetry. Second, we estimated to 0.19% the inhomogeneous strain from the Figure 1a diffractogram using the Williamson− Hall method with a Cauchy peak profile 38 (see Figure S1b), which is smaller than the value of 0.26% recently reported 39 but not negligible. This strain is probably due to hydroxyl groups coming from the barium precursor and remaining inside the NCs as point structural defects.…”