997 research outputs found
Fixed Volume Effect on Polar Properties and Phase Diagrams of Ferroelectric Semi-ellipsoidal Nanoparticles
For advanced applications in modern industry it is very important to reduce
the volume of ferroelectric nanoparticles without serious deterioration of
their polar properties. In many practically important cases fixed volume
(rather than fixed size) corresponds to realistic technological conditions of
nanoparticles fabrication. The letter is focused on the theoretical study of
the behavior of ferroelectric polarization, paramagnetoelectric coefficient and
phase diagrams of semi-ellipsoidal nanoparticles with fixed volume V. Our
approach combines the Landau-Ginzburg-Devonshire phenomenology, classical
electrostatics and elasticity theory. Our results show that the size effects of
the phase diagrams and polarization of semi-ellipsoidal BiFeO3 nanoparticles
nontrivially depends on V. These findings provide a path to optimize the polar
properties of nanoparticles by controlling their phase diagrams at a fixed
volume.Comment: 15 pages, 5 figures, we added the section IV. Paramagnetoelectric
(PME) coefficient at fixed volume in this version and changed title and
abstract accordingl
Local Magnetohydrodynamic Characteristics of the Plasma Stream generated by MPC
This paper investigates the spatial distributions of electrical current which flows inside the plasma stream generated by a magnetoplasma compressor (MPC). Two different modes of MPC operation with different gas supply scenarios have been applied in the experiments presented here. The first is the operation mode with a pulse injection of xenon into the interelectrode space, and the second is the operation mode with residual helium in the chamber and local injection of xenon directly into the compression zone. The maximum value of the electric current observed outside the MPC channel is 15 ÷ 20% of the total discharge current. Electric current vortices were discovered in the plasma stream. The amplitude of the current in the vortices reaches 50% of the total discharge current. The maximum EUV radiation power was measured in the mode of MPC operation with local xenon injection. Power in the wave range 12.2 ÷ 15.8 nm achieves up to 16 ÷ 18 kW
Local Magnetohydrodynamic Characteristics of the Plasma Stream generated by MPC
This paper investigates the spatial distributions of electrical current which flows inside the plasma stream generated by a magnetoplasma compressor (MPC). Two different modes of MPC operation with different gas supply scenarios have been applied in the experiments presented here. The first is the operation mode with a pulse injection of xenon into the interelectrode space, and the second is the operation mode with residual helium in the chamber and local injection of xenon directly into the compression zone. The maximum value of the electric current observed outside the MPC channel is 15 ÷ 20% of the total discharge current. Electric current vortices were discovered in the plasma stream. The amplitude of the current in the vortices reaches 50% of the total discharge current. The maximum EUV radiation power was measured in the mode of MPC operation with local xenon injection. Power in the wave range 12.2 ÷ 15.8 nm achieves up to 16 ÷ 18 kW
Electrocaloric Response of the Dense Ferroelectric Nanocomposites
Using the Landau-Ginzburg-Devonshire approach and effective media models, we
calculated the spontaneous polarization, dielectric, pyroelectric, and
electrocaloric properties of BaTiO core-shell nanoparticles. We predict
that the synergy of size effects and Vegard stresses can significantly improve
the electrocaloric cooling (2- 7 times) of the BaTiO nanoparticles with
diameters (10-100) nm stretched by (1-3)% in comparison with a bulk BaTiO.
To compare with the proposed and other known models, we measured the
capacitance-voltage and current-voltage characteristics of the dense
nanocomposites consisting of (28 -35) vol.% of the BaTiO nanoparticles
incorporated in the poly-vinyl-butyral and ethyl-cellulose polymers covered by
Ag electrodes. We determined experimentally the effective dielectric
permittivity and losses of the dense composites at room temperature. According
to our analysis, to reach the maximal electrocaloric response of the core-shell
ferroelectric nanoparticles incorporated in different polymers, the dense
composites should be prepared with the nanoparticles volume ratio of more than
25 % and fillers with low heat mass and conductance, such as Ag nanoparticles,
which facilitate the heat transfer from the ferroelectric nanoparticles to the
polymer matrix. In general, the core-shell ferroelectric nanoparticles
spontaneously stressed by elastic defects, such as oxygen vacancies or any
other elastic dipoles, which create a strong chemical pressure, are relevant
fillers for electrocaloric nanocomposites suitable for advanced applications as
nano-coolers.Comment: 38 pages, including 10 figures and 2 appendixe
- …