30 research outputs found
Peculiar Bi-ion dynamics in Na1/2Bi1/2TiO3 from terahertz and microwave dielectric spectroscopy
Dynamics of the main dielectric anomaly in Na1/2Bi1/2TiO3 (NBT) was studied
by time-domain THz and microwave spectroscopy, using also previously published
data and their new overall fits. Above the dielectric maximum temperature Tm ~
600 K, the response consists of coupled sub-THz oscillator and a relaxation
mode, assigned to strongly anharmonic Bi-ion vibrations and hopping, whose
slowing down explains the paraelectric-like permittivity increase to Tm. Below
Tm, the main relaxation continues slowing down and additional relaxation,
assigned to quasi-Debye losses, appears in the 10^11 Hz range. The oscillator
hardens on cooling and takes over the whole oscillator strength. The
permittivity decrease below Tm is caused by the reduced strength of the
relaxations due to dominance of the rhombohedral phase within the coexistence
region with the tetragonal phase. The anharmonic dynamics of Bi is supported by
previous structural studies. NBT represents a hybrid between standard and
relaxor ferroelectric behaviour
Pressure-induced changes in the optical properties of quasi-one-dimensional -NaVO
The pressure-induced changes in the optical properties of
-NaVO single crystals at room temperature were studied
by polarization-dependent Raman and far-infrared reflectivity measurements
under high pressure. From the changes in the Raman- and infrared-active phonon
modes in the pressure range 9 - 12 GPa a transfer of charge between the
different V sites can be inferred. The importance of electron-phonon coupling
in the low-pressure regime is discussed.Comment: 7 pages, 5 figure
Room temperature surface piezoelectricity in SrTiO3 ceramics via piezoresponse force microscopy
SrTiO3 ceramics are investigated by piezoresponse force microscopy.
Piezoelectric contrast is observed on polished surfaces in both vertical and
lateral regimes and depends on the grain orientation varying in both sign
(polarization direction) and amplitude. The observed contrast is attested to
the surface piezoelectricity due to flexoelectric effect (strain
gradient-induced polarization) caused by the surface relaxation. The estimated
flexoelectric coefficient is approximately one order of magnitude smaller as
compared to those recently measured in SrTiO3 single crystals. The observed
enhancement of piezoresponse signal at the grain boundaries is explained by the
dipole moments associated with inhomogeneous distribution of oxygen vacancies
Boxnep - модульный подводный робот перспективных технологий
The article discusses the relevance of the underwater vehicles are able to solve a wide range of problems. The decision puts in a basis of the research is designing a modular underwater robot. It allows to make a mounting of various equipment and testing it in the water medium. The paper deals with the concept of the robot and its characteristics