A5013435711- Ferroelectric and Piezoelectric Materials
- Multiferroics and related materials
- Acoustic Wave Resonator Technologies
- Microwave Dielectric Ceramics Synthesis
- Solid-state spectroscopy and crystallography
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Dielectric properties of ceramics
- Glass properties and applications
- Magnetic Properties and Synthesis of Ferrites
- Electronic and Structural Properties of Oxides
- Photorefractive and Nonlinear Optics
- Terahertz technology and applications
- Nuclear materials and radiation effects
- Nonlinear Optical Materials Research
- Optical properties and cooling technologies in crystalline materials
- Optical and Acousto-Optic Technologies
- Photonic and Optical Devices
- Luminescence Properties of Advanced Materials
- High-pressure geophysics and materials
- Topological Materials and Phenomena
- Physics of Superconductivity and Magnetism
- X-ray Diffraction in Crystallography
- Liquid Crystal Research Advancements
- Semiconductor materials and devices
Czech Academy of Sciences, Institute of Physics
2016-2025
Czech Academy of Sciences
2015-2024
Federal University of Agriculture
2023
Shanghai University
2019
Massachusetts Institute of Technology
2019
Institute of Physics
2018
Czech Academy of Sciences, Institute of Plasma Physics
2004-2017
Harvard University
2016
Changzhou University
2016
Brock University
2016
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...
$\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_{3}$ ceramics were investigated by means of infrared reflectivity and time domain terahertz transmission spectroscopy at temperatures $20--950\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the magnetodielectric effect was studied $10--300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ with magnetic field up to $9\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. Below $175\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, sum polar phonon contributions permittivity corresponds value measured...
The complex dielectric response of ${\mathrm{Bi}}_{1.5}{\mathrm{Zn}}_{1.0}{\mathrm{Nb}}_{1.5}{\mathrm{O}}_{7}$ cubic pyrochlore ceramics was investigated between 100 Hz and THz by a combination low-frequency capacitance bridges, high-frequency coaxial technique, time domain transmission spectroscopy, infrared spectroscopy. data obtained 10 K 400 revealed glasslike behavior: relaxation is observed over wide frequency temperature range, the permittivity loss maxima shift to higher values...
In the article we discuss dielectric response of relaxor-type complex perovskites in phonon-frequency region on basis a rich collection experimental data accumulated our laboratory by numerous infrared spectroscopy investigations over past decade. The effect cation occupational disorder and nanoscopic inhomogeneous polarisation is considered framework factor-group symmetry analysis effective-medium approach. Polar mode assignment comparison parameters different materials facilitated...
Infrared reflectivity, time-domain terahertz transmission, high-frequency dielectric measurements and Raman spectroscopy of Na0.5Bi0.5TiO3 complex ferroelectric perovskite were performed in a broad temperature range. The results analysed considering the macroscopic symmetry as well resulting from local Na–Bi ordering all three known phases. An overdamped infrared soft mode was revealed THz range which, together with central-mode type dispersion GHz range, contribute to strong permittivity...
The dielectric dispersion of the transparent relaxor ferroelectric ceramics PLZT 8/65/35 and 9.5/65/35 was determined in a wide frequency range including microwave infrared range. number observed polar phonons spectra gives evidence about locally broken cubic symmetry presence nanoclusters whole investigated temperature up to 530 K. A single broad symmetric that occurs below phonon frequencies fitted with Cole-Cole formula uniform distribution Debye relaxations. On decreasing temperature,...
An attempt has been undertaken to find a correlation between ionic parameters of ceramic materials and their complex permittivity at microwave frequencies. Ten Ba(B1/2′B1/2″)O3 perovskite compounds (B′=Y3+, In3+, Nd3+, Gd3+; B″=Nb5+, Ta5+ B′=Mg2+, Cd2+, B″=W6+) are compared in order study the effect radii, mass, valence state on dielectric properties. Fourier transform infrared reflectivity spectra 30–4000 cm−1 range were measured evaluated by means Kramers–Kronig analysis classical...
Cerium oxide (CeO 2 ) has been prepared as a ceramic dielectric resonator by conventional solid-state route.The sintered CeO high quality factor (Q؋f), Q value of 10 000 at 6 GHz with relative permittivity () 23, and temperature coefficient resonant frequency ( f ؊53 ppm/°C.The increases to 20 when the is doped 1 mol% CaCO 3 .Higher levels doping lowers values simultaneously decreases .TiO slightly , but deceases value.The pure 105 5.58 it cooled 30 K, whereas Ϸ 85 5.48 for 1-mol%-CaCO -doped K.W. A.
In this review we describe and discuss recent results on the linear dielectric response of high-permittivity crystals ceramics in wide frequency range 102–1014Hz. Our attention is paid to materials which exhibit some interesting low-frequency polar-phonon anomalies combination with additional dispersion below polar phonon region. The following compounds are discussed: microwave Bi1.5Zn1.0Nb1.5O7, antiferroelectric PbZrO3ceramics AgNbO3crystals, ferroelectric LiNaGe4O9, LaBGeO5, Cd2Nb2O7and...
The third-order ${E}^{2}{H}^{2}$-type magnetoelectric (ME) response of polycrystalline ${\text{EuTiO}}_{3}$ changes sign under magnetic bias and shows a large anomaly at the antiferromagnetic (AF)-paramagnetic phase boundary below ${T}_{\text{N}}\ensuremath{\approx}5.3\text{ }\text{K}$. It is attributed to critical fluctuations AF order parameter reinforced by quantum paraelectric polar correlations. underlying biquadratic spin-lattice coupling involves electric field induced...
X-ray diffraction, dynamical mechanical analysis and infrared reflectivity studies revealed an antiferrodistortive phase transition in EuTiO3 ceramics. Near 300K the perovskite structure changes from cubic Pm-3m to tetragonal I4/mcm due antiphase tilting of oxygen octahedra along c axis (a0a0c- Glazer notation). The is analogous SrTiO3. However, some ceramics as well single crystals show different spectra bringing evidence a crystal structure. In such samples electron diffraction...
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...
Dielectric spectroscopy in the submillimeter, millimeter, microwave, and radio frequency range has been performed between 300 600 K (for some cases below K) on nine Ba(B1/2′B1/2″)O3 complex perovskite ceramic compounds. The real part of permittivity ε′ decreases linearly with increasing tolerance factor t<1 approaching unity. It is insensitive to imperfections ceramic, such as impurities, vacancies, etc., entirely determined by polar lattice vibrations. Its temperature dependence...
Lattice dynamics for five ordered ${\mathrm{PbMg}}_{1∕3}{\mathrm{Nb}}_{2∕3}{\mathrm{O}}_{3}$ supercells were calculated from first principles by the frozen phonon method. Maximal symmetries of all are reduced structural instabilities. modes corresponding to these instabilities, equilibrium ionic positions, and infrared reflectivity spectra computed supercells. Results compared with our experimental data a chemically disordered PMN single crystal.