|Dielectric and IR spectroscopy||THz science and technology||Light and neutron scattering||
|Solid-state materials science||
Main activities of Department of Dielectrics cover experimental and theoretical investigations of high-permittivity insulators like liquid crystals, ferroelectrics, multiferroics, piezoelectrics, semiconductor nanostructures, and low-loss materials.
- Dielectric and IR spectroscopy
- THz science and technology
- Light and neutron scattering
- Theory and simulations
- Solid-state materials science
- Liquid crystals
The most significant fresh scientific results of our deparment are listed in the section Highlights.
Subterahertz collective dynamics of polar vortices
An artist take on the 'whirling' vibrational mode revealed in the polar vortex structure of PbTiO3/SrTiO3 superlattices [Nature 592, 376 (2021)] to highlight the front cover of the April issue of Nature.
Perovskites and other Framework Structure Materials
E. Buixaderas in collaboration with Prof. J. Dec contributed with the chapter: “Phonons and relaxations in unfilled tetragonal tungsten-bronzes” to a new book titled "Perovskites and other Framework Structure Materials: new trends and perspectives", published by Collaborating Academics IP, France.
Special Issue on the Contributions of Women in Ferroelectrics Research
Impressive schematic of the crystal structure of the tetragonal tungsten-bronze family made by Elena Buixaderas has been selected for the front cover in the IEEE TUFFC Special Issue on the Contributions of Women in Ferroelectrics Research and Development.
From superlattices to supercrystals
Researchers from Department of Dielectrics, in a world-wide collaboration led by Dr. Pavlo Zubko from University College London, have found that in superlattices, composed of layers of a ferroelectric material separated by thin metallic spacers, electric dipoles form an unusual pattern of nanoscale domains that order in three dimensions to create a ‘domain supercrystal’, exhibiting outstanding dielectric response.
Researchers' Night in the THz lab
Online art opening of the FZU Photo Competition 2020
Within European Researchers' Night on 27. November 2020 an online art opening of the FZU Photo Competition was performed. Alexey Bubnov got the 2nd place for his image of a beautiful liquid crystal texture resembling the Sun’s corona.
Ferroelectric phase transition in water molecules localized in mineral cordierite
We discovered that hydrogen bonds are eliminated and the Coulombic interactions dominate in water molecules localized in nano-channels of mineral cordierite. Their dipole moment is perpendicular to the channel axis c and our dielectric spectroscopy study have revealed their ordering at ~3 K. The critical relaxation tending to this ordering is polarized along the a-axis direction and lies in the radiofrequency range. Spontaneous polarization measurements yield the saturated value of ~3 nC/cm2 at 0.3 K [Nat. Commun. 11, 3927 (2020)].
Organic nanotubes created from mesogenic lactic acid derivatives
We found a facile route how to prepare nanotubes from rod-like mesogens dissolved in typical organic solvents. For selected types of chiral rod-like molecules, both enantiomers as well as the racemic mixtures, the nanotubes are formed by slow evaporation from a solution, regardless the solvent, concentration or deposition type. Obtained supramolecular assemblies were studied using various experimental techniques and nanotubes of 50-60 nm diameter described. We proposed rolling-up mechanism related to the surface tension difference at the opposite layer surfaces.
Mesoscopic polarization dynamics and two ferroelectric sublattices
in the uniaxial tetragonal tungsten bronze (Sr
The high-frequency dielectric behavior of uniaxial tungsten-bronze strontium barium niobate crystals with various Sr/Ba ratios have been studied in order to thoroughly understand the evolution of the relaxation dynamics across the ferroelectric phase transition. We showed that the dielectric response along the polar axis consists of three relaxations corresponding to polarization mechanisms related to several correlation lengths of mesoscopic order and that they are closly associated with two different ferroelectric subsystems.in the structure .
Raman scattering yields cubic crystal grain orientation
The anisotropy of Raman scattering was applied to determine the orientation of individual microcrystal grains, as small as a few µm, of GaV4S8 polycrystalline compound. This was possible by measuring polarised Raman spectra as a function of rotation of the sample along the laser direction. On comparing the resulting set of spectra with a computer simulation for particular symmetries, the orientation of the crystal grains could of the determined with good precision.