Size and temperature induced phase transition behaviors of barium titanate nanoparticles

Abstract

High density, almost impurity-free and defect-free barium titanate ͑BaTiO 3 ͒ fine particles with various sizes from 20 to 1000 nm were prepared by the two-step thermal decomposition of barium titanyl oxalate and postheating treatment. The crystal structures of these particles were investigated as a function of the size and the temperature using synchrotron radiation x-ray diffraction ͑XRD͒ measurement. As a result, the size-induced ferroelectric ͑tetragonal-cubic͒ phase transition observed at around 30 nm. Moreover, the temperature dependence of the crystal structures revealed that one phase transition at 135°C separated into two kinds of phase transition behaviors with decreased particle sizes, i.e., the tetragonal-cubic phase transition temperature was constant at 135°C despite particle sizes while the cell volume expansion temperature shifted to low temperature with decreasing particle sizes. Moreover, the temperature dependence of Raman scattering spectra clarified that the temperature at a discontinuous change of damping factor was almost consisted with the cell volume expansion temperature from the XRD measurement. These results suggested that the phase transition behavior of the BaTiO 3 nanoparticles was quite different from that of the BaTiO 3 single crystals.

Size effect of barium titanate: fine particles and ceramics

“…29) In the size effect of BaTiO 3 particles, the crystal structures of the three regions did not depend on particle sizes while only the volume fraction of these regions changes with particle size. The ferroelectricity is depressed with decreasing particle size and finally disappears below the critical size.…”

Scale effects and the formation of polarization vortices in tetragonal ferroelectrics

“…The wire is assumed to extend indefinitely out of the model plane, such that plane strain and plane electric field conditions apply. Minimum cross-sectional widths of 20nm were considered, noting that ferroelectricity has been observed in BaTiO3 structures from a few nanometers in size upwards [34][35][36]. The wire is assumed to be simply supported, with traction free surfaces.…”

Harvesting single ferroelectric domain stressed nanoparticles for optical and ferroic applications

“…13 An absence of mechanically induced strain is the most likely reason why chemically derived nanoparticles are not ferroelectric in small sizes. [16][17][18] The presence of surface strain in our nanoparticles was confirmed using the method of geometric phase analysis in which the phase component from an inverse Fourier transform is taken from a selected strong reflection in the Fourier transform of a HRTEM image. 19 This phase information has been used to construct an approximate strain map of individual nanoparticles, as shown in Fig.…”

“…A balance between corona emission from the razor blades and the Van de Graaff generator belt current maintains the applied potential at just below the dielectric breakdown threshold for the air gap between the razor blades and the grounded plate. Dried BaTiO 3 nanoparticles, prepared by mechanical grinding 15 or chemical precipitation, [16][17][18] are introduced as an aerosol suspension into the insulating column. Owing to the small size of the nanoparticles and their intrinsic dipole moment, it is very difficult to create a monoparticulate aerosol as the nanoparticles tend to clump into larger agglomerations.…”