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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Belyaev B. A., Drokin N. A., Shabanov V. F., Shepov V. N.
Заглавие : A study of the microwave dielectric permittivity of liquid crystals in electric and magnetic fields
Место публикации : Tech. Phys. - 1998. - Vol. 43, Is. 1. - P.105-109. - ISSN 1063-7842, DOI 10.1134/1.1258946
Примечания : Cited References: 8
Аннотация: A microwave detector based on a self-sustained oscillator circuit is proposed as a means to investigate the real and imaginary components of the dielectric permittivity of liquid crystals in external electric and magnetic fields. Results are given for measurements of a 500 MHz oscillator frequency for two types of nematic crystals, 5CBP and MBBA. Fundamental regularities are identified in the behavior of the microwave dielectric permittivity of samples in electric and magnetic fields. It is shown that the minimum of the high-frequency dielectric loss in liquid crystals correspond to a situation in which the long axes of the molecules are oriented parallel to the direction of the microwave electric field. (C) 1998 American Institute of Physics. [S1063-7842(98)02201-6].
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrova I. P., Seryukova I. V., Zherebtsova L. I.
Заглавие : Dielectric permittivity behavior at nonequilibrium processes in nh4hseo4 ferroelectrics
Место публикации : Fiz. Tverd. Tela. - 1985. - Vol. 27, Is. 11. - P.3438-3441. - ISSN 0367-3294
Примечания : Cited References: 5
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kuz'menko A. M., Mukhin A. A., Ivanov V. Y., Kadomtseva A. M., Lebedev S. P., Bezmaternykh L. N.
Заглавие : Antiferromagnetic Resonance and Dielectric Properties of Rare-earth Ferroborates in the Submillimeter Frequency Range
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 113, Is. 1. - P113-120. - ISSN 1063-7761, DOI 10.1134/S106377611105013X
Примечания : Cited References: 27. - This work was supported by the Russian Foundation for Basic Research, project no. 10-02-00846.
Предметные рубрики: GDFE3(BO3)(4)
SPECTROSCOPY
CRYSTAL
Ключевые слова (''Своб.индексиров.''): antiferromagnetic resonance--basic parameters--effective anisotropy constant--ferroborates--ferroics--ferromagnetic orderings--frequency ranges--magnetic interactions--magnetoresonance--millimeter frequency range--rare earth ions--submillimeters--antiferromagnetic materials--crystallography--erbium--europium--ferromagnetic resonance--ion exchange--magnetic anisotropy--magnetic devices--magnetic structure--permittivity--resonance--antiferromagnetism
Аннотация: The magnetoresonance and dielectric properties of a number of crystals of a new family of multiferroics, namely, rare-earth ferroborates RFe(3)(BO(3))(4) (R = Y, Eu, Pr, Tb, Tb(0.25)Er(0.75)), are studied in the submillimeter frequency range (nu = 3-20 cm(-1)). Ferroborates with R = Y, Tb, and Eu exhibit permittivity jumps at temperatures of 375, 198, and 58 K, respectively, which are caused by the R32 - P3(1)2(1) phase transition. Antiferromagnetic resonance (AFMR) modes in the subsystem of Fe(3+) ions are detected in the range of antiferromagnetic ordering (T T(N)
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Kharkov A. M., Filipson G. Y.
Заглавие : Magnetic capacitance in variable-valence manganese sulfides
Место публикации : Phys. Status Solidi B. - 2020. - Vol. 257, Is. 5. - Ст.1900637. - ISSN 03701972 (ISSN), DOI 10.1002/pssb.201900637
Примечания : Cited References: 12. - This study was supported by the Russian Foundation for Basic Research No. 18-32-00079 mol_a. The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science No. 18-42-240001 r_a
Аннотация: The permittivity of TmxMn1–xS (0 < x < 0.15) solid solutions is measured in the frequency range of 102–106 Hz at temperatures of 300–500 K in magnetic fields of up to 12 kOe. The migration and relaxation conductivity contributions to the electric polarization are established. The relaxation time and activation energy are calculated using the Debye model. A decrease in the capacitance and relaxation time in a magnetic field is observed. The electron polarization relaxation channel provided by recombination of the electron–hole pairs is found using the infrared spectroscopy investigations.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Belyaev B. A., Tyurnev V. V.
Заглавие : Electrodynamic calculation of effective electromagnetic parameters of a dielectric medium with metallic nanoparticles of a given size
Место публикации : J. Exp. Theor. Phys. - 2018. - Vol. 127, Is. 4. - P.608-619. - ISSN 10637761 (ISSN), DOI 10.1134/S1063776118100114
Примечания : Cited References: 31. - This work was supported by the Ministry of Education and Science of the Russian Federation (contract no. 14.575.21.0142; unique identifier of the project is RFMEFI57517X0142).
Ключевые слова (''Своб.индексиров.''): electromagnetic fields--magnetic susceptibility--metals--nanoparticles--natural frequencies--permittivity
Аннотация: The frequency dependence of the effective complex permittivity and effective complex permeability of a heterostructure based on a dielectric medium containing metallic nanoparticles of spherical shape is calculated by an original method. In contrast to the Bruggeman [21] and the Maxwell Garnett [17] approaches, which use the quasi-static approximation in calculations, a nonuniform distribution of electromagnetic fields inside metallic particles is calculated, which allows the analysis of the electromagnetic parameters of the heterostructure not only as a function of frequency but also as a function of the nanoparticle size. It is shown that the plasmon resonant frequency decreases with increasing both the size and the concentration of particles in the heterostructure. It is also shown that a dielectric medium containing nonmagnetic metallic nanoparticles exhibits diamagnetic properties. In this case, the position of the maximum on the frequency dependence of the imaginary part of the magnetic susceptibility coincides with the relaxation frequency of charge carriers. The calculated spectra of the real and imaginary components of the permittivity of the heterostructure with a size of metallic particles less than 10 nm are in good agreement with Bruggeman calculations; however, the agreement with Maxwell Garnett calculations is observed only at nanoparticle concentrations lower than 10–6.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Belyaev B. A., Tyurnev V. V., Khodenkov S. A.
Заглавие : The effective permittivity of an anisotropic composite of spheroidal particles in a dielectric matrix
Место публикации : Tech. Phys. Lett. - 2022. - Vol. 48, Is. 3. - P.110-114. - ISSN 10637850 (ISSN), DOI 10.1134/S1063785022040058
Примечания : Cited References: 10. - This study was carried out within the framework of state order FEFE-2020-0013 of the Ministry of Science and Higher Education of the Russian Federation
Аннотация: The concentration dependences of the effective permittivity have been obtained for an anisotropic composite consisting of a dielectric matrix filled with codirectional particles in the form of oblate or prolate ellipsoids of revolution (spheroids). The calculation has been made by solving numerically a system of coupled quadratic and integral equations obtained using the rigorous modification of the quasi-static Bruggeman theory. It is shown that the traditional simplified modification of the Bruggeman theory, which is widely used for calculating anisotropic composites, leads to errors of different signs for electromagnetic waves of the longitudinal and transverse polarizations relative to the spheroid axes. The dependences of the errors on the particle concentration are nonmonotonic and extrema observed in them can exceed 100%. The positions and values of the extrema depend strongly on the ellipticity of particles and the contrast of their permittivity with that of the matrix.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Udod L. V., Sitnikov M. N., Shestakov N. P.
Заглавие : Bi2(Sn0.95Cr0.05)2O7: Structure, IR spectra, and dielectric properties
Место публикации : Ceram. Int.: Elsevier, 2016. - Vol. 42, Is. 4. - P.5177-5183. - ISSN 02728842 (ISSN), DOI 10.1016/j.ceramint.2015.12.040
Примечания : Cited References: 45. - This work was supported by the Russian Foundation for Basic Research Projects no. 15-42-04099 r_siberia_a, Siberian Branch of Science and NAS of Belarus “Electronic and magnetic phase transitions in materials with magnetoelectric affect” and government work no. 114090470016.
Предметные рубрики: BISMUTH PYROSTANNATE
PYROCHLORE STRUCTURE
MAGNETIC-PROPERTIES
PARTIAL OXIDATION
HIGH-TEMPERATURE
X-RAY
Bi2Sn2O7
SUBSTITUTION
CATALYSTS
DIFFRACTION
Ключевые слова (''Своб.индексиров.''): bismuth pyrostannate--infrared absorption spectra--structural transition--permittivity--debye model
Аннотация: Infrared absorption spectra of the bismuth pyrostannate Bi2(Sn0.95Cr0.05)2O7 were investigated in the frequency range 350-1100 cm-1 at temperatures of 110-525 K. Four frequency regions with split absorption lines are distinguished. Softening of frequencies at the structural transitions was observed. The maxima of permittivity measured in the frequency range 1-200 kHz at temperatures 100-400 K were determined. It was found that the magnetic susceptibility changes its sign in the low-temperature region. The correlation between anomalies in the magnetic susceptibility, permittivity, and absorption line intensity was established. Softening of frequencies is explained by the variation in the coefficient of thermal expansion of the lattice. The temperature behavior of permittivity is described using the Debye model. © 2015 Elsevier Ltd and Techna Group S.r.l.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bikbaev R. G., Vetrov S. Ya., Timofeev I. V.
Заглавие : The optical Tamm states at the interface between a photonic crystal and nanoporous silver
Место публикации : J. Opt.: IOP, 2017. - Vol. 19, Is. 1. - Ст.015104. - ISSN 20408978 (ISSN), DOI 10.1088/2040-8986/19/1/015104
Примечания : Cited References: 38. - The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research project № 16-42-243065, SB RAS No. II.2P (0358-2015-0010), the Ministry of Education and Science of the Russian Federation, projects no. 3.1276.2014/K and no. 3.1211.2017/PCH. I.V.T. acknowledges financial support from RFBR research project № 15-02-03838.
Ключевые слова (''Своб.индексиров.''): photonic crystal--nanoporous silver--optical tamm state--effective permittivity
Аннотация: The optical Tamm states (OTSs) localized at the edges of a photonic crystal bounded by a nanoporous silver (NPS) film are investigated. NPS involves spherical vacuum nanopores dispersed in the metal matrix and is characterized by the effective resonance permittivity. The transmission, reflection, and absorption spectra of the structures under study at the normal incidence of light are calculated. It is shown that each Tamm state has its own frequency range where the real part of effective permittivity is negative. The light field localization at the high- and low-frequency OTSs is investigated. The specific features of spectral manifestation of the OTSs are studied in dependence on the nanopore concentration in the metal matrix and on the NPS film thickness.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bobrov P. P., Mironov V. L., Repin A. V.
Заглавие : Dielectric permittivity spectra of oil-water-saturated sandy-clayey rocks of different mineralogical compositions and relaxation properties of water in these rocks
Коллективы : RFBR [12-05-00502a, 14-05-00151a]
Место публикации : Russ. Geol. Geophys.: Elsevier Science, 2015. - Vol. 56, Is. 7. - P.1065-1073. - ISSN 1068-7971, DOI 10.1016/j.rgg.2015.06.007
Примечания : Cited References: 21. - This work was supported by RFBR (grant nos. 12-05-00502a and 14-05-00151a).
Предметные рубрики: MOIST SOILS
FREQUENCY
MODEL
TEMPERATURE
SALINITY
RANGE
GHZ
Ключевые слова (''Своб.индексиров.''): conductivity--dielectric permittivity--multifrequency dielectric relaxation--oil-bearing deposits--sandy-clayey rocks
Аннотация: Experimental measurements of the dielectric permittivity and equivalent conductivity of sandy-clayey samples (a mixture of river sand with bentonite or kaolin) saturated with salt-solution-diesel-fuel emulsions were performed in the frequency range from 10 kHz to 1 GHz at temperatures of 25-65 °C. It is shown that when the content of the salt solution in the saturating fluid does not exceed 10%, the dielectric permittivity in the frequency range from 1 MHz to 1 GHz depends little on the mineral composition of the sample and on the concentration of the saturating solution. When the portion of water is 33.3% or higher, increasing the concentration of the salt solution leads to an increase in the equivalent conductivity and the real part of the complex dielectric permittivity. Using the refractive model of the complex dielectric permittivity, we have estimated the dielectric properties of bound water, which depend on temperature and the type of clay (bentonite or kaolin) in the sand-clay mixture but are independent of the water saturation and the amount of clay in the sample.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bobrov P. P., Kroshka E. S., Muzalevskiy K. V.
Заглавие : The effect of dielectric relaxation processes on the complex dielectric permittivity of soils at frequencies from 10 kHz to 8 GHz—Part II: Broadband analysis
Колич.характеристики :11 с
Место публикации : IEEE Trans. Geosci. Remote Sens. - 2024. - Vol. 62. - Ст.2000411. - ISSN 01962892 (ISSN), DOI 10.1109/TGRS.2023.3340693. - ISSN 15580644 (eISSN)
Примечания : Cited References: 51
Аннотация: This article is the second in a series evaluating the effect of dielectric relaxation processes on the relatively effective complex dielectric permittivity (RCP) of soils. Part II is based on the results of experimental measurements in the frequency range 10 kHz to 8–20 GHz. The broadband dielectric spectrum model includes the high-frequency part as a model of the dielectric mixture and the relaxation part as the sum of three relaxation processes modeled by the Debye and Cole–Cole formulas. For modeling the high-frequency part of the spectrum, the Dobson and Mironov models were considered as possible options. As stated in Part I, the influence of relaxation processes on the imaginary part of the RCP extends up to frequencies of units of gigahertz. The increase in the imaginary part in these models was compensated by unrealistically high values of the specific electrical conductivity of free and bound water. We examined the correspondence of these models to experimental data at frequencies above 2–5 GHz, assuming that the conductivity of bound and free water is zero. The parameters of relaxation processes were found while solving the least-square optimization problem using the technique for determining the continuous distribution of relaxation times (DRTs). Found process parameters depend on the content of clay, organic carbon, and moisture of the samples. The more clay is in the soil, the greater the strength of these processes is. The influence of organic carbon with the conditions being equal consists in the reduction of the real and imaginary parts of RCP.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : Bound states in the continuum with high orbital angular momentum in a dielectric rod with periodically modulated permittivity
Коллективы : Ministry of Education and Science of Russian Federation [N 3.1845.2017]; RFBR [16-02-00314]
Место публикации : Phys. Rev. A: American Physical Society, 2017. - Vol. 96, Is. 1. - Ст.013841. - ISSN 2469-9926, DOI 10.1103/PhysRevA.96.013841. - ISSN 2469-9934(eISSN)
Примечания : Cited References:38. - We acknowledge discussions with D. N. Maksimov and A. S. Aleksandrovsky. This work was partially supported by Ministry of Education and Science of Russian Federation (State Contract No. N 3.1845.2017) and RFBR Grant No. 16-02-00314.
Предметные рубрики: PHOTONIC CRYSTAL SLABS
LIGHT-CONE
RESONANCES
SPHERES
RADIATION
Аннотация: We report bound states in the radiation continuum (BICs) in a single infinitely long dielectric rod with periodically stepwise modulated permittivity alternating from ε1 to ε2. For ε2 = 1 in air the rod is equivalent to a stack of dielectric disks with permittivity ε1. Because of rotational and translational symmetries the BICs are classified by orbital angular momentum m and the Bloch wave vector beta directed along the rod. For m = 0 and β = 0 the symmetry protected BICs have definite polarization and occur in a wide range of the radius of the rod and the dielectric permittivities. More involved BICs with m ≠ 0, β = 0 exist only for a selected radius of the rod at a fixed dielectric constant. The existence of robust Bloch BICs with β ≠ 0, m = 0 is demonstrated. Asymptotic limits to a homogeneous rod and to very thin disks are also considered.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : Scattering plane waves by a dielectric cylinder with periodically modulated permittivity at oblique incidence
Коллективы : Ministry of Education and Science of Russian Federation [3.1845.2017]; Russian Foundation for Basic Research [16-02-00314]
Место публикации : Phys. Rev. A. - 2018. - Vol. 97, Is. 6. - Ст.063856. - ISSN 2469-9926, DOI 10.1103/PhysRevA.97.063856. - ISSN 2469-9934(eISSN)
Примечания : Cited References: 24. - We acknowledge discussions with A. A. Bogdanov and D. N. Maksimov. This paper was partially supported by Ministry of Education and Science of Russian Federation (State Contract No. 3.1845.2017) and Russian Foundation for Basic Research Grant No. 16-02-00314.
Предметные рубрики: BOUND-STATES
FANO RESONANCE
LIGHT LINE
CONTINUUM
ARRAYS
Аннотация: For scattering of electromagnetic waves by a dielectric cylinder with periodically modulated permittivity we focus on the vicinity of the frequency of the wave with regard to the eigenfrequencies of bound states in the continuum. Then response of the cylinder becomes extremely sensitive to the angle of incidence and polarization of the plane wave. The cross section of the scattering of electromagnetic waves with mixed polarization undergoes crucial change from the Bragg shape to the Fano shape by rotation of the polarization that paves a way to tuning of Fano resonances by an external source.
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13.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Aleksandrov K. S., Turchin P. P., Sorokin B. P., Karpovich A. A., Nefedov V. A.
Заглавие : Bulk acoustic waves propagation in Li2B4O7 piezoelectric crystals under the static uniaxial mechanical pressure
Коллективы : Annual frequency control symposium
Место публикации : Proceedings of the Annual IEEE International Frequency Control Symposium/ Annual frequency control symposium (54 ; 2000 ; Jun. ; 7-9 ; Kansas, MO). - 2000. - P.214-217. - ISBN 01616404
Примечания : Cited References: 8
Ключевые слова (''Своб.индексиров.''): acoustic wave transmission--acoustic wave velocity--elasticity--lithium compounds--mathematical models--permittivity--piezoelectricity--pressure effects--single crystals--electromechanical constants--piezoelectric crystal--piezoelectric materials
Аннотация: The influence of uniaxial mechanical stresses on bulk acoustic waves velocity in piezoelectric crystals Li2B4O7 has been investigated. Electromechanical constants have determined.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Eremin E. V., Sablina K. A., Sapronova N. V.
Заглавие : Dielectric properties of a mixed-valence Pb3Mn7O15 manganese oxide
Коллективы :
Разночтения заглавия :авие SCOPUS: Dielectric properties of a mixed-valence Pb3Mn7O 15 manganese oxide
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2010. - Vol. 22, Is. 37. - Ст.375901. - ISSN 0953-8984, DOI 10.1088/0953-8984/22/37/375901
Примечания : Cited References: 14. - This study was supported by the Russian Foundation for Basic Research 'Siberia', project No. 09-02-98003, and the Siberian Branch of the Russian Academy of Sciences, integration project No. 101.
Ключевые слова (''Своб.индексиров.''): cation--lead--manganese derivative--oxide--article--chemical model--chemistry--crystallization--electric conductivity--electronics--methodology--temperature--cations--crystallization--electric conductivity--electronics--lead--manganese compounds--models, chemical--oxides--temperature--ac electric field--analysis of resistivity--carrier hopping--charge ordering--complex dielectric constant--crystal site--debye models--dielectric constants--dielectric spectra--frequency windows--lattice sites--low frequency--manganese ions--mixed valence--mixed valence state--relaxation behaviors--temperature range--electric fields--manganese--manganese oxide--permittivity--single crystals--crystal symmetry
Аннотация: We investigated the low-frequency dielectric properties of a Pb3Mn7O15 single crystal with manganese ions in the mixed-valence state (Mn3+/Mn4+). Dielectric relaxation was found in the frequency window from 20 to 100 kHz in the temperature range 110-180 K. The dielectric spectra of the crystal were analyzed using a Debye model. Estimations made within the model and analysis of resistivity data suggest that the relaxation behavior of the dielectric constant is related to polaronic charge carrier hopping. Around 250 K, charge ordering occurs in the crystal when the Mn3+ and Mn4+ ions are arranged in a specific order among the crystal sites. With a decrease in temperature, an ac electric field can induce a charge hop between the equivalent lattice sites available, related to crystal symmetry. This hopping is equivalent to the reorientation of an electric dipole that yields Debye-type behavior of the complex dielectric constant. The observed anisotropy in the behavior of the dielectric properties and resistivity can be attributed to a pronounced two-dimensional character of the crystal structure.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S., Udod L. V., Sitnikov M. N., Kretinin V. V., Molokeev M. S., Mironova-Ulmane N.
Заглавие : Dipole glass in chromium-substituted bismuth pyrostannate
Коллективы : Russian Foundation for Basic Research [N 18-52-00009 Bel_a, 18-32-00079 mol_a, 3.5743.2017/6.7]
Место публикации : Mater. Res. Express. - 2018. - Vol. 5, Is. 11. - Ст.115202. - ISSN 2053-1591, DOI 10.1088/2053-1591/aaddd9
Примечания : Cited References: 33. - This study was supported by the Russian Foundation for Basic Research project N 18-52-00009 Bel_a, No 18-32-00079 mol_a, the state order No 3.5743.2017/6.7.
Предметные рубрики: BI4TI3O12 THIN-FILMS
NEUTRON-DIFFRACTION
RAMAN-SPECTROSCOPY
BI2SN2O7
Ключевые слова (''Своб.индексиров.''): dipole glass--permittivity--polarization--raman scattering spectra--structural transition
Аннотация: To establish the existence of dipole glass in the chromium-substituted bismuth pyrostannate solid solutions, the frequency and temperature dependences of the permittivity have been measured in the temperature range of 300–750 K. The field and dynamic dependences of polarization in the temperature range of 80–550 K have been determined. Using the Raman scattering spectra, the absence of inversion center has been established. The maximum of electrical resistance has been found in the vicinity of the dipole moment freezing point. The carrier type has been determined from the thermopower data. The polarization relaxation is shown to be nonexponential. The experimental data are explained within the model of dipole glass in the α- phase and the model of charged crystalline domain walls with the electron-polarization relaxation mechanism above the α–β structural transition.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Fokina V. D., Bovina A. F., Bogdanov E. V., Pogoreltsev E. I., Laptash N. M.
Заглавие : Disorder and phase transitions in oxyfluoride (NH4)(3)Ta(O-2)(2)F-4
Место публикации : J. Fluor. Chem. - 2011. - Vol. 132, Is. 10. - P.713-718. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2011.05.012
Примечания : Cited Reference Count: 19. - Гранты: This work was supported by the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation (NSh-4645.2010.2).Финансирующая организация: Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-4645.2010.2]
Предметные рубрики: HEAT-CAPACITY
COMPLEXES
RB2KTIOF5
FLUORIDES
CRYOLITE
Ключевые слова (''Своб.индексиров.''): cubic oxyfluorides--structural disorder--phase transitions--entropy--permittivity--pressure effect--cubic oxyfluorides--entropy--permittivity--phase transitions--pressure effect--structural disorder
Аннотация: Calorimetric, X-ray, dielectric and DTA under pressure measurements have been performed on oxyfluoride (NH4)(3)Ta(O-2)(2)F-4. The succession of nonferroelectric phase transitions was found associated with the order-disorder processes. The comparative analysis tantalate with related niobate has revealed the important role of the central atom in the physical properties behavior, mechanism of structural distortions and barocaloric effect in oxyfluorides with the eight-coordinated anionic polyhedra. (C) 2011 Elsevier By. All rights reserved.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mikhaleva E. A., Flerov I. N., Kartashev A. V., Gorev M. V., Molokeev M. S., Bogdanov E. V., Bondarev V. S., Korotkov L. N., Rysiakiewicz-Pasek E.
Заглавие : Effect of restricted geometry and external pressure on the phase transitions in ammonium hydrogen sulfate confined in a nanoporous glass matrix
Место публикации : J. Mater. Sci. - 2018. - Vol. 53, Is. 15. - P.12132–12144. - ISSN 00222461 (ISSN), DOI 10.1007/s10853-018-2467-1
Примечания : Cited References: 44. - The reported study was funded by Russian Foundation for Basic Research (RFBR) according to the Research Project No. 16-32-00092 mol_a.
Ключевые слова (''Своб.индексиров.''): hydraulics--hydrostatic pressure--permittivity--pore size--specific heat--sulfur compounds--thermal expansion
Аннотация: A study of heat capacity, thermal dilatation, susceptibility to hydrostatic pressure, permittivity and polarization loops was carried out on NH4HSO4–porous glass nanocomposites (AHS + PG) as well as empty glass matrices. The formation of dendrite clusters of AHS with a size, dcryst, exceeding the pore size was found. An insignificant anisotropy of thermal expansion of AHS + PG showing statistically uniform distribution of AHS with random orientations of nanocrystallites over the matrix was observed. The effect of internal and external pressures on thermal properties and permittivity was studied. At the phase transition P-1 ↔ Pc, a strongly nonlinear decrease in the entropy ΔS2 and volume strain (ΔV/V)T2 was observed with decreasing dcryst. The linear change in temperatures of both phase transitions P-1 ↔ Pc ↔ P21/c under hydrostatic pressure is accompanied by the expansion of the temperature range of existence of the ferroelectric phase Pc, while this interval narrows as dcryst decreases.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Markevich I. A., Selyutin G. E., Drokin N. A., Selyutin A. G.
Заглавие : Electrical and mechanical properties of the high-permittivity ultra-high-molecular-weight polyethylene-based composite modified by carbon nanotubes
Место публикации : Tech. Phys. - 2020. - Vol. 65, Is. 7. - P.1106-1113. - ISSN 10637842 (ISSN), DOI 10.1134/S1063784220070129
Примечания : Cited References: 39
Аннотация: A composite based on ultra-high-molecular-weight polyethylene (UHMWPE) added with 1 wt % of multiwalled carbon nanotubes (MWCNTs) with a high permittivity (ε = 4.5) and a low dielectric loss (tanδ = 10–2) in the frequency range from 100 Hz to 100 MHz has been synthesized, and its main mechanical characteristics have been studied. The material has a low (22 MPa) breaking strength, a high (700%) tensile elongation, and an abrasion resistance higher than that of pure UHMWPE by 37%. It is shown using the X-ray diffraction and differential scanning calorimetry data that the changes in the mechanical properties of the composite are related to the changes in the polymer matrix structure under the action of the high-intensity ultrasonic radiation used for embedding MWCNTs into the polymer.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Drokin N. A., Kiiko V. S., Malkin A. I., Pavlov A. V.
Заглавие : Electrophysical properties of BeO + 30 wt.% TiO2 ceramics sintered at elevated temperatures
Место публикации : Refract. Ind. Ceram. - 2022. - Vol. 63, Is. 3. - P.315-320. - ISSN 1083-4877 (ISSN), DOI 10.1007/s11148-022-00728-3. - ISSN 1573-9139 (eISSN)
Примечания : Cited References: 11
Аннотация: The electrophysical properties of BeO-based ceramics with introduced micro- and nanoparticles of TiO2 were investigated by impedance spectroscopy in the frequency range of 100 Hz – 100 MHz. In order to increase the density and conductivity, the initial ceramic components were sintered at the highest possible temperatures up to 1660°C, followed by annealing in hydrogen at 800°C. In this case, TiO2 was strongly reduced with the formation of lower titanium oxides (Ti3O5) along with metallic titanium. When interacting with hydrogen, TiH2 is formed. For the first time, impurity phases were found in (BeO + TiO2) ceramics, which can significantly alter its bulk and surface properties. The resulting ceramics has a high reach-through conductivity, which increases significantly after an additional thermal annealing in hydrogen. It was established that the activation energy of conductivity does not depend much on the concentration of TiO2 nanoparticles and decreases significantly in the low-temperature region. The method of constructing equivalent electrical circuits was used to simulate the passage of the active and reactive components of the current through the complex internal structure of the ceramics.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dudnik A. I., Vnukova N. G., Drokin N. A., Bondarev V. S., Shestakov N. P., Tomashevich Y. V., Churilov G. N.
Заглавие : Electrophysical properties of hydroxylated endohedral metallofullerene with gadolinium
Место публикации : J. Phys. Chem. Solids. - 2019. - Vol. 135. - Ст.109094. - ISSN 00223697 (ISSN) , DOI 10.1016/j.jpcs.2019.109094
Примечания : Cited References: 35. - The reported study was funded by RFBR according to the research project No 18-29-19003.
Аннотация: The paper presents the results of experimental measurements of constitutive and electrophysical properties in hydroxylated endohedral metallofullerene with gadolinium sample. We extracted endohedral metallofullerene from carbon condensate, synthesized in high-frequency arc discharge plasma. Later hydroxyl groups were added. Via methods of infrared and x-ray photoelectronic spectroscopy, it was established that the molecules of hydroxylated endohedral metallofullerene have the Gd@C82Ox(OH)y, x + y=(40–42) composition. The method of measuring the electrical impedance in the frequency range from 100 Hz to 100 MHz shows that the resulting hydroxylated fullerene is an ion conductor. The measured frequency dependences of the dielectric permittivity and conductivity of hydroxylated fullerene are explained based on the assumption of an inhomogeneous distribution of electric charges in the material volume. Dielectric-hysteresis loops in the frequency range of 25 Hz–1 MHz and temperature range of 80–300 K, and volt-ampere characteristics were measured. The obtained results imply the appearance of residual polarization induced by the electric field in hydroxylated fullerene. However, the constant dipole moment is absent. © 2019
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