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Department of Dielectrics

Institute of Physics of the Czech Academy of Sciences


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Light and neutron scattering

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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.

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The ferroelectric phase transition of the tetragonal tungsten-bronze SBN-35 unveiled

The structural ferroelectric-paraelectric transition has been definitely observed by electron diffraction tomography in the tetragonal tungsten-bronze (TTB) Sr0.35Ba0.61Nb2O6.04 (SBN-35) from the paraelectric group P4/mbm to the ferroelectric Pmbm. At 625 K, the refined structure shows that the average structure of SBN-35 is tetragonal with an almost negligible orthorhombic distortion [Fig.1].

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Přibramite, a new Se-containing mineral from the Czech Republic, characterized by Raman spectroscopy

Minerals containing selenium are interesting and worthy to study due to its inherent photovoltaic effect. The characterization and understanding of these natural minerals is important to be able to make synthetic analogues.

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Fast polarization mechanisms in uniaxial tungsten-bronze SBN-81

The high-frequency dielectric response of the uniaxial strontium barium niobate (SrxBa1−xNb2O6) crystals with 81% of Sr (x = 0.81) was studied from 1 kHz to 30 THz along the polar axis in a wide temperature interval [E. Buixaderas et al, Sci. Rep. 7, 18034 (2017)]. Relaxor properties were observed in the complex dielectric response and four main excitations were ascertained below the phonon frequencies. These fast polarization mechanisms take place at THz, GHz and MHz ranges and show different temperature evolution.

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Macroscopic heterophase pattern in Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals

Polarization dependence of the Raman scattering intensities demonstrate that lamellar structures observed in (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) single crystals are composed of tetragonal-like and rhombohedral-like layers extending over macroscopic (mm) lengths.

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Compositional behaviour of phonons in Pb(Zr1-xTix)O3 ceramics

Raman spectra of PZT ceramics were studied systematically in a broad temperature interval (10–600 K) and a broad Ti/Zr concentration range around the morphotropic phase boundary (x = 0.25–0.70) [ E. Buixaderas et al., Phys. Rev. B 91, 014104 (2015) ].

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Polar fluctuations of nanoscale size as a source of giant dielectric response of relaxor ferroelectrics

Characteristic frequencies of nanoscale polar fluctuations have been resolved by means of neutron diffuse scattering measurements on a Sr0.61Ba0.39Nb2O6 single crystal in the MHz-GHz frequency region.

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Catching intermediate phases in antiferroelectric single crystals

Ferroelectric and antiferroelectric single crystals show phase transitions that can be evidence by different experimental methods. In this work we investigated single crystals of antiferroelectric PbZrO3 substituted with 1% of Ti (PZT 99/1) by means of optical microscopy, micro-Raman scattering, second harmonic generation and dielectric spectroscopy, on heating to and cooling from its cubic phase.

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New experimental method allowed to record dispersion curves of polar lattice modes in magnetoelectric BiFeO3

Bismuth ferrite (BiFeO3) is a prototypical multiferroic system exhibiting extraordinary properties; it is ferroelectric up to TC ~ 1100 K as well as antiferromagnetic up to TN ~ 640 K. Characterisation of polar phonon modes is essential for understanding its dielectric and electromechanical behaviour.

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