In this study the comparison of dielectric behaviour of BaTi
1-x
Zr
x
O
3
(BTZx) ceramic samples prepared by means of a solid state and mechanochemical synthesis was presented. A single phase of ...perovskite structure was identified in the samples at room temperature. No significant impurities were detected in an EDS spectrum and the samples had a good stoichiometric ratio. The morphology of the investigated samples was characterized by a scanning electron microscopy (SEM). The investigation of dielectric properties of the BTZx samples within the temperature range from 140 K to 600 K was performed by means of a dielectric spectroscopy method at the frequency ranging from 0.1 Hz to 10 MHz. The temperature dependences of real part of dielectric permittivity showed the changes of the character of the paraelectric-ferroelectric (PE-FE) phase transition for the ceramic samples obtained by means of both methods.
The relaxor behavior of barium zirconium titanate ceramics BaZr
0.35
Ti
0.65
O
3
prepared by a conventional sintering process was investigated. The synthesized material was determined by an X-ray ...diffraction and scanning electron microscopy. Based on performed studies, the BaZr
0.35
Ti
0.65
O
3
ceramic material has been identified as canonical relaxor, related to the Ti-rich polar regions. The freezing temperature T
f
and activation energy E
a
are calculated from the Vogel-Fulcher relationship.
Increasing of Sr
0.7
Bi
0.2
TiO
3
concentration in Na
0.5
Bi
0.5
TiO
3
-Sr
0.7
Bi
0.2
TiO
3
solid solutions causes increasing of Bi/Na relation and vacancies in the A-site of perovskite structure. In ...temperature dependence of dielectric permittivity, such a change of composition is reflected by transforming of the frequency-dependent shoulder into a maximum characteristic for relaxor ferroelectrics and diminishing of the frequency-independent maximum characteristic for Na
0.5
Bi
0.5
TiO
3
. Here changes in behavior of dielectric permittivity and polarization are studied if PbTiO
3
is added in a certain concentration range of Na
0.5
Bi
0.5
TiO
3
-Sr
0.7
Bi
0.2
TiO
3
solid solutions. Changes of the characteristic temperatures as a function of PbTiO
3
concentration are determined. Behavior of the electrocaloric effect is compared with the results obtained for Na
0.5
Bi
0.5
TiO
3
-SrTiO
3
-PbTiO
3
.
Thermophysical Reactivity Control of RBMK-1000 Vorobiev, Aleksander V.; Antonova, Aleksandra M.; Vinogradov, Maksim P.
EPJ Web of Conferences,
01/2016, Letnik:
110
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
In this paper, viewed thermophysical characteristics of the moderator water graphite reactor RBMK. Indicated possibilities of controlling thermal state of graphite stack by regulation composition of ...the purge gas. Presents experimental results, but static thermal state characteristics of graphite moderator RBMK-1000. Developed a software code for integral characteristic engineering calculations, that determine value of margin reactivity reactor RBMK-1000, in the slow transients.
For the corresponding two-dimensional continued fractions with complex partial numerators that belong to certain subsets of the Cartesian product of two angular sets in the right half plane and ...partial denominators equal to one, we establish sufficient conditions for the uniform convergence and an estimate for the truncation error by using an analog of the method of fundamental inequalities, relations for the real and imaginary parts of the tails of figured approximants, and a multidimensional analog of the Stieltjes–Vitali theorem.
The differences between the physical properties of barium titanate BaTiO3 and newly obtained BaHfxTi1-xO3 were identified. These ceramics were prepared by solid-phase reaction from simple oxides and ...carbonates using the conventional method. The structure and morphology of investigated samples were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The application of impedance spectroscopy made possible to characterize of these materials in the terms of electrical properties.
The temperature and frequency dependencies of the dielectric susceptibility in relaxor electro-optical PLZT 8/65/35 modified with 3d transition-metal ions (Mn, Fe, Co, Ni) measured to study the aging ...and memory effects are reported. The studies of aging at room temperature show that 3d admixtures (Me) in PLZT 8/65/35 ceramics at small to medium concentration range (Me < 1.0 wt.%) change the depth of dispersion, the aging amplitude and the temperature range of the memory effect. At admixture concentrations Me →1.0 wt% the aging and memory effect are significantly reduced (or eliminated).
The obtained results suggest that aging effects are determined by two substantial acceptor effects of the introduced ions: 1) formation of Me
2+
- V
O
(oxygen vacancy) dipoles and 2) Jahn-Teller effect.
The barium titanate (BaTiO
3
) and the BaTiO
3
+ 0.1wt.% Eu
2
O
3
ceramics were prepared by a conventional ceramic method. The structural studies were carried out by means of an X-ray diffraction ...technique. The influence of the grains and the grain boundaries on the electrical properties was investigated using a impedance spectroscopy. This technique enables us to determine the values of grain and grain boundary resistance. The results show that the Eu doping leads to a significant reduction in the resistance value of the grains (˜10
5
Ω) with respect to the pure BT ceramics (˜10
7
Ω). The conductivity processes were determined from the Arrhenius behaviour of grain and grain boundary resistances.
Thermal expansion, Raman and dielectric properties of the lead-free (1−x)Na
0.5
Bi
0.5
TiO
3
-xSrTiO
3
(x = 0, 0.08 and 0.1) ceramic solid solutions, fabricated by the conventional solid-state ...reaction method, were investigated. The Sr-doping results in an increase of the dielectric permittivity, broadening of the permittivity maximum, enhancement of the relaxation near depolarization temperature, broadening of the Raman bands and shift of all anomalies toward lower temperatures. The observed effects are attributed to an increase of the degree of cationic disorder and enhancement of the relaxor-like features. Anomalies in the thermal expansion strain were observed at the temperatures corresponding to the dielectric anomalies but not related to any phase transitions. These anomalies are supposed to follow changes of the averaged unit cell volume in the temperature interval of tetragonal and rhombohedral phase coexistence.
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