A5060313790- Ferroelectric and Piezoelectric Materials
- Multiferroics and related materials
- Microwave Dielectric Ceramics Synthesis
- Acoustic Wave Resonator Technologies
- Solid-state spectroscopy and crystallography
- X-ray Diffraction in Crystallography
- Photorefractive and Nonlinear Optics
- Glass properties and applications
- Crystal Structures and Properties
- Crystallization and Solubility Studies
- Nuclear materials and radiation effects
- Advanced Condensed Matter Physics
- Luminescence Properties of Advanced Materials
- Inorganic Chemistry and Materials
- Crystallography and molecular interactions
- Theoretical and Computational Physics
- Advanced ceramic materials synthesis
- Magnetic and transport properties of perovskites and related materials
- Magnetic properties of thin films
- High-pressure geophysics and materials
- Electronic and Structural Properties of Oxides
- Thermal Expansion and Ionic Conductivity
- Intermetallics and Advanced Alloy Properties
- Chemical and Physical Properties of Materials
- Earthquake Detection and Analysis
Czech Academy of Sciences
2015-2024
Czech Academy of Sciences, Institute of Physics
2015-2024
University of Oxford
2023
Xi'an Jiaotong University
2021-2023
Australian National University
2010-2019
Institut Laue-Langevin
2019
University of the Free State
2011
Peter the Great St. Petersburg Polytechnic University
2010
Polish Academy of Sciences
2006-2010
Stony Brook University
2010
Polar nanoregions in relaxor ferroelectrics were modeled by the Monte Carlo method. To account for correlations between atomic shifts, Potts-like models applied with a random field used to mimic chemical disorder impact on polar ordering. The diffuse scattering effects generated structures calculated and compared neutron x-ray experimental data known from literature. An alternative explanation of diffraction contrary ``pancakes'' concept reported several recent papers is given. Generated...
We present a fully atomistic model of polar nanoregions (PNRs) in the relaxor ferroelectric PbMg${}_{1/3}$Nb${}_{2/3}$O${}_{3}$. Our molecular dynamics calculations reproduce both characteristic form neutron diffuse scattering distribution and its temperature dependence. A shell was used with modified version published interatomic potential that based on ab initio calculations. The parameters this were optimized for work to provide better description O atom interactions, as these are...
Domain structures play a crucial role in the electric, mechanical and other properties of ferroelectric materials. In this study, we uncover physical origins enigmatic zigzag domain structure prototypical multiferroic material BiFeO$_3$. Using phase-field simulations within Landau-Ginzburg-Devonshire framework, demonstrate that spatially-homogeneous defect charges result closely resemble those observed experimentally. The acquired understanding underlying physics pyramidal-domain formation...
It is well known that disordered relaxor ferroelectrics exhibit local polar correlations. The origin of localized fields disrupt long range order for different substitution types, however, unclear. Currently, it substituents the same valence as Ti4+ at B-site barium titanate lattice produce random disruption Ti-O-Ti chains induces behavior. On other hand, investigating and behavior resulting from more complex due to simultaneous occurrence charge imbalances displacements substituent cation....
The three dimensional distribution of the X-ray diffuse scattering intensity BaTiO$_3$ has been recorded in a synchrotron experiment and simultaneously computed using molecular dynamics simulations shell-model. Together these have allowed details disorder paraelectric to be clarified. narrow sheets scattering, related famous anisotropic longitudinal correlations Ti ions, are shown caused entirely by overdamped anharmonic soft phonon branch. This finding demonstrates that occurrence agrees...
A combined neutron diffuse scattering study and model analysis of the antiferroelectric crystal PbZrO 3 is described. Following on from earlier X-ray studies, supporting evidence for disordering oxygen octahedral tilts Pb displacements shown in high-temperature cubic phase. Excess intensity found at M R points Brillouin zone. shell-model molecular dynamics simulation closely reproduces pattern. Both in-phase antiphase are structural model, with predominating. The transition between...
Dynamics of the main dielectric anomaly in Na1/2Bi1/2TiO3 (NBT) were studied by time-domain THz and microwave spectroscopy, using also previously published data their new overall fits. Above maximum temperature Tm ≈ 600 K, response consists coupled sub-THz oscillator a relaxation mode, assigned to strongly anharmonic Bi-ion vibrations hopping, whose slowing down explains paraelectric-like permittivity increase Tm. Below Tm, continues additional relaxation, quasi-Debye losses, appears 1011 Hz...
Typical magnetic skyrmion is a string of inverted magnetization within ferromagnet, protected by sleeve vortexlike spin texture, such that its cross-section carries an integer topological charge. Some magnets form antiskyrmions, the antiparticle strings which carry opposite Here we demonstrate topologically equivalent but purely electric antiskyrmion can exist in ferroelectric material as well. In particular, our computer experiments reveal archetype ferroelectric, barium titanate, host...
Incommensurate satellite reflections modulating along the 〈110〉* directions have been observed in electron diffraction patterns of single crystals relaxor ferroelectric Pb 2 ScTaO 6 (PST) recorded via transmission microscopy. The satellites occur characteristically within a specific temperature range and display differing or variable modulation vectors relative to their primary reflections. represent weak frustrated antiferroelectric state PST, termed incommensurate (IAFE) state. IAFE...
We present a joint theoretical and experimental study on diffuse scattering in cubic PbZrO3. A comprehensive synchrotron data-set reveals ⟨110⟩-oriented streaks emanating from Bragg reflections showing strong intensity variation the vicinity of selected M points. The distribution hk12 section another system weaker but much sharper q1212 -type lines extended along ⟨100⟩directions. These are slightly bent intersect little off points Brillouin zone. Molecular dynamics simulations with an ab...
The work describes a first-principles-based computational strategy for studying structural phase transitions, and in particular, determination of the so-called Landau-Devonshire potential---the classical zero-temperature limit Gibbs energy, expanded terms order parameters. It exploits configuration space attached to eigenvectors modes frozen ground state, rather than spanned by unstable high-symmetry phase, as done usually. This allows us carefully probe part energy surface vicinity which is...
Antiferroelectric perovskites form an important family of functional electric materials, which have high potential in energy storage and conversion applications. However, a full understanding their crystal structural formation is still lacking. ${\mathrm{PbZrO}}_{3}$-based materials can serve as model system for investigation, not only because ${\mathrm{PbZrO}}_{3}$ was the first discovered antiferroelectric, but also it undergoes typical phase transition sequence from high-temperature...
The excellent properties of modern ferroelectrics are the result nanoscale local structure phenomena. Diffuse scattering, sensitive to atomic correlations, is one few techniques that able provide detailed information on polar order. A review diffuse scattering studies in given with special emphasis those works where computer simulation used analyse experimental data. examples comprise some well known materials, such as NaNO2 or BaTiO3, but also ferroelectrics: lead-based relaxors, bismuth...
The dielectric permittivity and properties of electrically active lattice resonances in nanotwinned BiFeO_{3} crystals have been studied theoretically using an earlier established interatomic potential. results suggest that array 71° domain walls with about 2-5 nm spacing enhances the static by more than order magnitude. This enhancement is associated excitation, corresponding to a collective vibration pinned at remarkably high frequency 0.3 THz.
Pair distribution function analysis of neutron-scattering data and ab initio molecular dynamics results have been employed to study short-range structural correlations their temperature dependence in a heavily disordered dielectric material ${\mathrm{Sr}}_{x}{\mathrm{Ba}}_{1\ensuremath{-}x}{\mathrm{Nb}}_{2}{\mathrm{O}}_{6}\phantom{\rule{4pt}{0ex}}(x=0.35,\phantom{\rule{0.28em}{0ex}}0.5$, 0.61). Intrinsic disorder caused by partial occupation the cationic sites differently sized Sr Ba atoms...
Herein, the properties of broadband dielectric spectra up to THz–infrared range (1 − x )BaTiO 3 ‐ BaZrO (BZT‐ ) solid solution are reviewed and complemented. This includes proper ferroelectric ( = 0), diffuse ferroelectrics (0 < ≤ 0.2), relaxor (0.4 0.8), dipolar glasses > normal 1). The characterized by an overdamped central mode in microwave which weakens on cooling. Except for BaTiO , soft do not soften appreciably contribute substantially low‐frequency permittivity maximum. most...
The mechanism of the prototype ferroelectric phase transition in BaTiO3 is a matter intense debate and to large extent still wrapped mystery. Precursor phenomena form polarized clusters paraelectric are by now believed represent key step into phenomenon. determination slower dynamics cluster polarization flipping along with faster order−disorder Ti hopping mode among ⟨111⟩ off-center sites suggests coexistence, instead mutual exclusion, displacive types, initially proposed as distinct...
X-ray diffuse scattering in the paraelectric phase of ${\text{Cd}}_{2}{\text{Nb}}_{2}{\text{O}}_{7}$ is measured and structurally interpreted using atomistic methods. Ab initio molecular-dynamics simulations show dynamic disorder both sublattices with average displacements Cd ions significantly larger than for Nb. Within octahedral ${\text{NbO}}_{6}$ zigzag CdO chains along $⟨110⟩$ rather strong longitudinal correlations ion are found whereas transverse component weakly correlated. Local...
Melting of a particle lattice in two dimensional systems substantially differs from the one three dimensions. The most prominent theory melting 2D, formulated by Kosterlitz, Thouless, Halperin, Nelson, and Young (KTHNY), describes solid-liquid phase transition as two-step process, where solid turns into liquid via hexatic phase. microscopic nature this process lies excitation unbinding topological defects 2D lattice. KTHNY scenario has been observed number physical systems. Here, we...
Perovskite solid solutions PbHfO3-PbSnO3 offer valuable opportunities for studying the formation mechsnisms of incommensurate phases, owing to presence an intermediate (between cubic and incommensurate) phase, which is stabilized in PbHfO3 upon PbSnO3 admixture. Here, x-ray diffuse scattering signal used quantify evolution susceptibilities related different modes distortion (ferroelectric, incommensurate, antiferrodistortive) as a function temperature results are critically compared...
Pb(Hf1−xSnx)O3 single crystals with x = 0.23 were characterized using single-crystal x-ray diffraction in the wide temperature range. The information on structure of two intermediate phases, situated between low antiferroelectric and high paraelectric has been obtained. lower-temperature AFE2 phase is by incommensurate displacive modulations Pb sublattice. higher IM rotations oxygen octahedra, primarily form anti-phase tilts, which are also present phase. For same crystal, 119Sn Mossbauer...
$\mathrm{Pb}{\mathrm{Zr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}$ exhibits an antiferroelectric-ferroelectric phase boundary at the composition $x\ensuremath{\sim}0.06$. Around this boundary, several questions need to be answered, such as stabilizations of different phases with a small amount compositional difference, sequence transitions, coexistence crystal structures, and potential applications. In work, we have carried out systematic structural investigations single crystals...