A5013014208- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Ferroelectric and Piezoelectric Materials
- Crystallography and molecular interactions
- Solid-state spectroscopy and crystallography
- Microwave Dielectric Ceramics Synthesis
- Crystal structures of chemical compounds
- Multiferroics and related materials
- Acoustic Wave Resonator Technologies
- Liquid Crystal Research Advancements
- Crystal Structures and Properties
- Nonlinear Optical Materials Research
- Magnetic and transport properties of perovskites and related materials
- Dielectric properties of ceramics
- Surfactants and Colloidal Systems
- Electronic and Structural Properties of Oxides
- Bone Tissue Engineering Materials
- Chemical Thermodynamics and Molecular Structure
- Optical and Acousto-Optic Technologies
- Organometallic Compounds Synthesis and Characterization
- Molecular spectroscopy and chirality
- Nuclear materials and radiation effects
- Perovskite Materials and Applications
- Magnetic Properties and Applications
- Photorefractive and Nonlinear Optics
Czech Academy of Sciences
2012-2024
Czech Academy of Sciences, Institute of Physics
2012-2023
Czech Academy of Sciences, Institute of Plasma Physics
2007-2021
National Institute for Materials Science
2012
Stockholm University
2010
Osaka University
2010
National Academy of Sciences of Ukraine
2008
Czech Academy of Sciences, Institute of Inorganic Chemistry
2006
Institute of Physics
1977-2001
Jožef Stefan Institute
1998
Thorough Raman and infrared (IR) reflectivity investigations of nominally pure ${\mathrm{SrTiO}}_{3}$ ceramics in the 10--300 K range have revealed a clear presence polar phase whose manifestation steeply increases on cooling. The strengths Raman-forbidden IR modes are proportional to ${\ensuremath{\omega}}_{\mathrm{TO}1}^{\ensuremath{-}\ensuremath{\alpha}}(\ensuremath{\alpha}\ensuremath{\approx}1.6)$ where ${\ensuremath{\omega}}_{\mathrm{TO}1}$ is soft mode frequency. No pronounced...
The dielectric response to infrared waves polarized along the tetragonal axis of a ferroelectric single-domain crystal ${\mathrm{BaTiO}}_{3}$ was determined by time-domain THz spectroscopy and Fourier-transform reflectivity techniques. In addition three well-known polar lattice modes, experiment shows an additional mode relaxation type in spectral region, which accounts for Curie-Weiss behavior $c$-axis constant. A comparison experimental results with ab initio based effective-Hamiltonian...
High-frequency dielectric properties of A5B4O15 (A=Ba, Sr, Mg, Zn, Ca; B=Nb, Ta) ceramics are studied by means the microwave cavity technique, a combination far-infrared reflection and transmission spectroscopy time-resolved terahertz spectroscopy. Microwave permittivity ε′ Q×f factor vary, depending on chemical composition, between 11 51, 2.4 88 THz, respectively. The temperature coefficient τf varies −73 232 ppm/°C, in two samples |τf| is less than 15 ppm/°C. It shown that determined polar...
Infrared reflectivity and time-domain terahertz transmission spectra of EuTiO3 ceramics revealed a polar optic phonon at 6–300 K whose softening is fully responsible for the recently observed quantum paraelectric behaviour. Even if our show lower permittivity than single crystal due to reduced density and/or small amount secondary pyrochlore Eu2Ti2O7 phase, we confirmed magnetic field dependence permittivity, also slightly smaller in crystal. An attempt reveal soft 1.8 on up 13 T remained...
Infrared reflectivity spectra of cubic ${\text{SrMnO}}_{3}$ ceramics reveal 18% stiffening the lowest-frequency phonon below antiferromagnetic phase transition occurring at ${T}_{N}=233$ K. Such a large temperature change polar frequency is extraordinary and we attribute it to an exceptionally strong spin-phonon coupling in this material. This consistent with our prediction from first-principles calculations. Moreover, phonons become Raman active ${T}_{N}$, although their activation...
Dielectric spectra of two K0.5Na0.5NbO3 ceramics with different grain sizes (10 and 0.5 μm) were measured from 102 to 1014 Hz in a broad temperature range. The sequence first-order phase transitions (cubic-tetragonal-orthorhombic-rhombohedral) was detected by differential scanning calorimetry, dielectric spectroscopy, time-domain terahertz spectroscopy. size affects all the transitions, which are more smeared small-grain sample. In large-grain ceramics, well-separated near-Debye relaxations...
Ferroelectrics have been, among others, studied as electroactive implant materials. Previous investigations indicated that such implants induce improved bone formation. If a ferroelectric is immersed in liquid, an electric double layer and diffusion are formed at the interface. This decisive for protein adsorption bioactive behaviour, particularly adhesion growth of cells. The charge distribution can be characterized, simplified way, by zeta potential. We measured potential dependence on...
One of the purposes this work is to provide a crystallographic review group 1 and thallium rare-earth ternary sulfides M(+)Ln(3+)S2. We have therefore determined crystal structures KLaS2, KPrS2, KEuS2, KGdS2, KLuS2, KYS2, RbYS2, which belong α-NaFeO2 structural family (R3m), as well NaLaS2, derived from disordered NaCl type (Fm3m). The were compared with known members thallium(I) by standard tools crystal-chemical analysis such comparison bond-valences, interatomic distances unit-cell...
Abstract In this study, ceramic samples of lead zirconate titanate Pb(Zr0.42Ti0.58)O3 (PZT 42/58) doped with Fe (hard) and Nb (soft) were studied by Raman, infrared (IR) THz spectroscopy in the temperature range from 900 to 20 K. From evaluation IR Raman phonons undoped ceramics, we conclude that tetragonal PZT ceramics undergo a low-temperature phase transition tilted phase, revealed anomalies phonon parameters appearance new modes. Doped also presented similar behaviour. The main...
The dielectric response of ${\text{PbMg}}_{1/3}{\text{Nb}}_{2/3}{\text{O}}_{3}\text{\ensuremath{-}}35%{\text{PbTiO}}_{3}$ ceramics (close to the morphotropic phase boundary) from 100 Hz up THz was determined in a broad temperature range 5--900 K. Two were studied and compared: coarse grain (CGC) (grain size $\ensuremath{\sim}4\text{ }\ensuremath{\mu}\text{m}$) fine (FGC) $\ensuremath{\sim}150\text{ }\text{nm}$). Both showed similar polar-phonon ferroelectric transition near...
Seven inorganic salts of 3,5-diamino-1,2,4-triazole (dat) with acids were prepared within our project focused on the crystal engineering novel NLO materials and their X-ray structures determined. Three triclinic compounds, dat(1+) selenate dihydrate, sulphate dihydrate perchlorate, crystallize in space group P. monoclinic – i.e. nitrate, chloride hemihydrate hydrogen phosphite P21/c, P21/n respectively. Finally, most promising structure dihydrogen phosphate is orthorhombic (the Fdd2). The...
We prepared multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22 ceramics and compared their magnetic dielectric properties with single crystal. Magnetic susceptibility microwave resonance measurement revealed phase transition at TC=312 K, similar as in Ferroelectric (FE) can be induced by external field all investigated samples the diagram qualitatively resembles that of The range fields, where FE is induced, broadens after annealing Ceramics quenched sintering exhibit several orders...
Abstract A new series of ferroelectric liquid crystal materials containing a lateral methyl group on the aromatic ring alkoxybenzoate unit has been synthesized and investigated. These exhibit wide temperature range SmC* phase cooling (including supercooling) with very high spontaneous polarization. All transition temperatures are lower when compared those similar non-substituted materials. In comparison compounds methoxy group, only SmC*-Cr changed significantly. The values polarization...
Abstract Three series of ferroelectric liquid crystals have been synthesized, having three ester groups in the mesogenic core and one group chiral chain. The introduced into decrease temperature crystallization, which results a broad range smectic C phase homologues with long non-chiral These phases exhibit high spontaneous polarization relatively short pitch helical structure.
Three novel inorganic salts of aniline with sulfuric and selenic acids were prepared characterized by X-ray structural analysis. Anilinium(1+) selenate, (C6H5NH3+)2SeO42−, anilinium sulfate, (C6H5NH3+)2SO42−, crystallize in the monoclinic space groupC2. The crystal structures are based on hydrogen bonded layers alternating cations anions. selenate dihydrate, (C6H5NH3+)2SeO42−·2H2O, crystallizes groupC2/c. structure is formed a network cations, anions water molecules connected system...
Pb2MnTeO6, a new double perovskite, was synthesized. Its crystal structure determined by synchrotron X-ray and powder neutron diffraction. Pb2MnTeO6 is monoclinic (I2/m) at room temperature with regular arrangement of all the cations in their polyhedra. However, when lowered to ∼120 K it undergoes phase transition from I2/m C2/c structure. This accompanied displacement Pb atoms center polyhedra due 6s2 lone-pair electrons, together surprising off-centering Mn2+ (d5) magnetic cations. strong...
The temperature dependence of the optical phonons and high-frequency microwave excitations morphotropic $\mathrm{Pb}(\mathrm{Z}{\mathrm{r}}_{1\ensuremath{-}x}\mathrm{T}{\mathrm{i}}_{x}){\mathrm{O}}_{3}$ (PZT) ceramics with compositions PZT 52/48 53/47 were studied by a broadband spectroscopy approach, using Raman, far-infrared, time-domain terahertz (THz), spectroscopies. A careful evaluation evolution phonon parameters clearly revealed only two macroscopic phase transitions intrinsic...
We performed factor-group analysis of all phonons in possible monoclinic C2/c and C2 structures BiMnO3 compared it with our experimental infrared Raman spectra. conclude that the crystal structure is centrosymmetric whole investigated temperature range from 10 to 550 K, therefore cannot be ferroelectric. revealed a dielectric relaxation THz spectra above structural phase transition taking place at TC1 = 475 K giving evidence strong lattice anharmonicity large dynamical disorder Bi cations...
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...