共查询到20条相似文献,搜索用时 15 毫秒
1.
A. V. Semirov D. A. Bukreev V. O. Kudryavtsev A. A. Moiseev A. A. Gavrilyuk A. L. Semenov G. V. Zakharov 《Technical Physics》2009,54(11):1586-1590
The effect of temperature and elastic tensile stresses on the magnetoimpedance of an amorphous Vitrovac 6025Z (Fe4CO67Mo1.5Si16.5B11) foil is studied. Two temperature ranges (20–70 and 70–220°C) in which the effect of elastic tensile stresses on the magnetoimpedance
has different characters are detected. The existence of these two temperature ranges is shown to be caused by a change in
the sign of a magnetostriction constant at 70°C. 相似文献
2.
G. V. Kurlyandskaya A. V. Semirov V. A. Lukshina E. G. Volkova S. O. Volchkov D. A. Bukreev A. A. Moiseev 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1466-1468
The structure and magnetic properties and the magnetoimpedance effect of nanocrystalline Fe73.5Si16.5B6Nb3Cu1 alloy ribbons, obtained from the amorphous state by annealing under different conditions, were comparatively analyzed. Despite
the similarity of the samples’ structural states and the processes of their quasi-static magnetization reversal, the features
of the magnetoimpedance effect are indicative of significant differences in the processes of their dynamic magnetization. 相似文献
3.
S. Kabi A. Ghosh 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,79(4):377-381
Electrical complex ac conductivity of the compound
Li0.9[Ni1/3Mn1/3Co1/3]O1.95 has been studied in the
frequency range 10 Hz–2 MHz and in the temperature range 93–373 K. It
has been observed that the frequency dependence of the ac conductivity obeys
a power law and the temperature dependence of the ac conductivity is quite
weak. The experimental data have been analyzed in the framework of several
theoretical models based on quantum mechanical tunneling and classical
hopping over barriers. It has been observed that the electron tunneling is
dominant in the temperature range from 93 K to 193 K. A crossover of
relaxation mechanism from electron tunneling to polaron tunneling is
observed at 193 K. Out of the several models discussed, the electron
tunneling and the polaron tunneling models are quite consistent with the
experimental data for the complex ac conductivity. The various parameters
obtained from the fits of the experimental results for the real and
imaginary parts of the conductivity to the predictions of these models are
quite reasonable. 相似文献
4.
Priyadarshini S. Sahoo Anuradha Panigrahi Sunanda K. Patri Ram N. P. Choudhary 《Central European Journal of Physics》2008,6(4):843-848
Polycrystalline samples of Ba4SrRTi3V7O30 (R=Sm and Dy), members of the tungsten-bronze family, were prepared using a high-temperature, solid-state reaction technique
and studied their electrical properties (using complex impedance spectroscopy) in a wide range of temperature (31–500°C) and
frequency (1 kHz-1 MHz). Preliminary structural (XRD) analyses of these compounds show the formation of single-phase, orthorhombic
structures at room temperature. The scanning electron micrographs (SEM) provided information on the quality of the samples
and uniform distribution of grains over the entire surface of the samples. Detailed studies of the dielectric properties suggest
that they have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 432 and 355°C
for R= Sm and Dy, respectively, at frequency 100 kHz). Measurements of electrical conductivity (ac and dc) as a function of
temperature suggest that the compounds have semiconducting properties much above the room temperature, with negative temperature
coefficient of resistance (NTCR) behavior. The existence of ferroelectricity in these compounds was confirmed from a polarization
study.
相似文献
5.
The Ac electrical conductivity and the dielectric relaxation properties of the [(C3H7)4N]2Cd2Cl6 polycrystalline sample have been investigated by means of impedance spectroscopy measurements over a wide range of frequencies
and temperatures, 209 Hz–5 MHz and 361–418 K, respectively. The purpose is to make a difference between the electrical and
dielectric properties of the polycrystalline sample and single crystal. Besides, a detailed analysis of the impedance spectrum
suggests that the electrical properties of the material are strongly temperature-dependent. Plots of (Z" versus Z') are well
fitted to an equivalent circuit model consisting of a series combination of grains and grains boundary elements. Moreover,
the temperature dependence of the electrical conductivity in the different phases follows the Arrhenius law and the frequency
dependence of σ (ω) follows the Jonscher’s universal dynamic law. Furthermore, the modulus plots can be characterized by full
width at half height or in terms of a nonexperiential decay function φ(t) = exp(t/t)β. Finally, the imaginary part of the permittivity constant is analyzed with the Cole–Cole formalism. 相似文献
6.
T. M. Ul’yanova N. P. Krut’ko L. V. Titova Yu. G. Zonov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(4):603-608
The correlation between temperature treatment conditions and the ratio of components in nanostructured fibrous powders with
a composition of ZrO2-Y2O3-Al2O3 and their porous crystal structure and physicochemical properties is studied. The dependences of the ratio between zirconia
tetragonal and monoclynic phases on the treatment temperature and the alumina content are found to have a nonmonotonic character.
The growth of zirconia crystallite size is suppressed by introduced nanocrystalline alumina in a temperature range of 600–1200°C,
which is caused by the processes of ternary solid solution formation. The bulk and picnometric density values of materials
are proportional to the temperature of heat treatment. The temperature dependence of the specific surface and the size of
oxide grain particles has an inversely proportional character. With increasing alumina content in the powders, the specific
surface increases, while the picnometric and bulk densities decrease. 相似文献
7.
S.K. Barik R.N.P. Choudhary P.K. Mahapatra 《Applied Physics A: Materials Science & Processing》2007,88(1):217-222
Complex impedance analysis of a valence-compensated perovskite ceramic oxide Na1/2Sm1/2TiO3, prepared by a mixed oxide (solid-state reaction) method, has been carried out. The formation of single-phase material was
confirmed by X-ray diffraction studies, and it was found to be an orthorhombic phase at room temperature. In a scanning electron
microscope, grains separated by well-defined boundaries are visible, which is in good agreement with that of impedance analysis.
Alternating current impedance measurements were made over a wide temperature range (31–400 °C) in an air atmosphere. Complex
impedance and modulus plots helped to separate out the contributions of grain and grain boundaries to the overall polarization
or electrical behavior. The physical structure of the samples was visualized most prominently at higher temperatures (275 °C)
from the Nyquist plots showing inter- and intragranular impedance present in the material. The frequency dependence of electrical
data is also analyzed in the framework of the conductivity and modulus formalisms. The bulk resistance, evaluated from the
impedance spectrum, was observed to decrease with rise in temperature, showing a typical negative temperature coefficient
of resistance-type behavior like that of semiconductors. The modulus mechanism indicates the non-Debye type of conductivity
relaxation in the materials, which is supported by the impedance data.
PACS 77.22.Ch; 77.22.Ej; 77.22.Gm; 77.22.Jp; 77.84.Bw 相似文献
8.
A few compositions in the system Ba1???x La x SnO3 (x?=?0.00, 0.01, 0.05, and 0.10) have been synthesized via the solid state ceramic route. The synthesized powders have been characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, Raman spectroscopy, Fourier transformation infrared, thermogravimetrical analysis, and differential thermal analysis techniques. The powder X-ray diffraction pattern of the samples confirms the formation of a single-phase solid solution only up to 0.50?≤?x. It was found that all the samples have a cubic crystal structure. The electrical properties of La-modified BaSnO3 were studied using ac impedance spectroscopy technique over a wide range of temperatures (50–650 °C) in the frequency range of 10 Hz–13 MHz. The complex impedance plots above 300 °C show that total impedance is due to the contributions of grain and grain boundaries. The resistance of these contributions has been determined. Variation of these resistances with temperature shows the presence of two different regions with different slopes. The nature of the variation of conductivity of the grain and grain boundaries is different in different regions. Based on the value of activation energy, it is proposed that conduction via hopping of doubly ionized oxygen vacancies (VO ??) is taking place in the temperature region of 300–450 °C, whereas in the temperature region of 450–650 °C, it is due to proton, i.e., OH? ions, hopping. 相似文献
9.
LiSn2P3O12 with sodium (Na) super ionic conductor (NASICON)-type rhombohedral structure was successfully obtained at low sintering temperature, 600 °C via citric acid-assisted sol-gel method. However, when the sintering temperature increased to 650 °C, triclinic structure coexisted with the rhombohedral structure as confirmed by X-ray diffraction analysis. Conductivity–temperature dependence of all samples were studied using impedance spectroscopy in the temperature range 30 to 500 °C, and bulk, grain boundary and total conductivity increased as the temperature increased. The highest bulk conductivity found was 3.64?×?10?5 S/cm at 500 °C for LiSn2P3O12 sample sintered at 650 °C, and the lowest bulk activation energy at low temperature was 0.008 eV, showing that sintering temperature affect the conductivity value. The voltage stability window for LiSn2P3O12 sample sintered at 600 °C at ambient temperature was up to 4.4 V. These results indicated the suitability of the LiSn2P3O12 to be exploiting further for potential applications as solid electrolytes in electrochemical devices. 相似文献
10.
Banarji Behera Pratibindhya Nayak Ram N. P. Choudhary 《Central European Journal of Physics》2008,6(2):289-295
A polycrystalline sample of KCa2Nb5O15 with tungsten bronze structure was prepared by a mixed oxide method at high temperature. A preliminary structural analysis
of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound shows a uniform
grain distribution throughout the surface of the sample. Studies of temperature variation on dielectric response at various
frequencies show that the compound has a transition temperature well above the room temperature (i.e., 105°C), which was confirmed
by the polarization measurement. Electrical properties of the material have been studied using a complex impedance spectroscopy
(CIS) technique in a wide temperature (31–500°C) and frequency (102–106 Hz) range that showed only bulk contribution and non-Debye type relaxation processes in the material. The activation energy
of the compound (calculated from both the loss and modulus spectrum) is same, and hence the relaxation process may be attributed
to the same type of charge carriers. A possible ‘hopping’ mechanism for electrical transport processes in the system is evident
from the modulus analysis. A plot of dc conductivity (bulk) with temperature variation demonstrates that the compound exhibits
Arrhenius type of electrical conductivity.
相似文献
11.
A. V. Semirov D. A. Bukreev A. A. Moiseev V. A. Lukshina E. G. Volkova S. O. Volchkov 《Russian Physics Journal》2011,54(5):612-618
The influence of the thermal treatment type on the temperature dependences of the magnetoimpedance of nanocrystalline Fe73.5Si16.5B6Nb3Cu1 alloy strips is investigated. The main mechanisms determining the temperature behavior of the magnetoimpedance of strips
with induced magnetic anisotropy having various special features are established. The prospects for application of the alloy
strips nanocrystallized in the presence of a magnetic field as sensitive elements of temperature sensors and special magnetic
field detectors are demonstrated. 相似文献
12.
Y. Köseoğlu M. Bay M. Tan A. Baykal H. Sözeri R. Topkaya N. Akdoğan 《Journal of nanoparticle research》2011,13(5):2235-2244
We present a systematic investigation on the structural and magnetic properties of Mn0.2Ni0.8Fe2O4 nanoparticles synthesized by a polyethylene glycol (PEG)-assisted hydrothermal route. XRD, FT-IR, TEM and VSM were used for
the structural, morphological, dielectric properties and magnetic investigation of the products, respectively. Average crystallite
size of product was estimated using Line profile fitting as 6 ± 1 nm and particle size as 6.5 ± 1.0 nm from TEM micrographs.
Magnetization measurements have shown that the particles have a blocking temperature of 134 K. Magnetization and the coercive
field of the sample increase by decreasing the temperature. The conductivity measurements reveal the semiconducting behaviour
for the sample. Temperature-dependent dielectric properties: dielectric permittivity (ε) and ac conductivity (σac) for the sample were studied as a function of applied frequency in the range from 1 Hz to 3 MHz. These studies indicated
that the dielectric dispersion curve for the sample showed usual dielectric dispersion which can be explained on the basis
of Koop’s theory, which is based on the Maxwell–Wagner model for the interfacial polarization of homogeneous double structure. 相似文献
13.
L. M. Kubalova V. I. Fadeeva 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(5):670-672
Ni80Mo7B13 nanocrystalline alloy containing a Ni(Mo,B) face-centered cubic (FCC) solid solution of the substitutional-interstitial type
was obtained by high-energy ball milling of the component mixtures. In the temperature range 400–700°C, the metastable solid
solution Ni(Mo,B) decomposes, leading to the formation of metastable FCC Ni(Mo) and HCP MoB4 phases. Upon isothermal annealing at 1000°C for1 h, the alloy transforms into the stable state and contains the equilibrium
phases FCC Ni(Mo), cubic Ni21Mo2B6, and orthorhombic Ni3B. 相似文献
14.
A. V. Malakhovskii E. V. Eremin D. A. Velikanov A. V. Kartashev A. D. Vasil’ev I. A. Gudim 《Physics of the Solid State》2011,53(10):2032-2037
The magnetic properties of the Nd0.5Gd0.5Fe3(BO3)4 single crystal have been studied in principal crystallographic directions in magnetic fields to 90 kG in the temperature
range 2–300 K; in addition, the heat capacity has been measured in the range 2–300 K. It has been found that, below the Néel
temperature T
N = 32 K down to 2 K, the single crystal exhibits an easy-plane antiferromagnetic structure. A hysteresis has been detected
during magnetization of the crystal in the easy plane in fields of 1.0–3.5 kG, and a singularity has been found in the temperature
dependence of the magnetic susceptibility in the easy plane at a temperature of 11 K in fields B < 1 kG. It has been shown that the singularity is due to appearance of the hysteresis. The origin of the magnetic properties
of the crystal near the hysteresis has been discussed. 相似文献
15.
In this work, Li2SnO3 has been synthesized by the sol–gel method using acetates of lithium and tin. Thermogravimetric analysis (TGA) has been applied to the precursor of Li2SnO3 to determine the suitable calcination temperature. The formation of the compound calcined at 800 °C for 9 h has been confirmed by X-ray diffraction (XRD) analysis. The Li2SnO3 is then pelletized and electrically characterized by using electrochemical impedance spectroscopy (EIS) in the frequency range from 50 Hz to 1 MHz. The complex impedance spectra clearly show the dominating presence of the grain boundary effect on electrical properties whereas the complex modulus plots reveal two semicircles which are due to the grain (bulk) and grain boundary. The spectra of imaginary parts of both impedance and modulus versus frequency show the existence of peaks with the modulus plots exhibiting two peaks that are ascribed to the grain and grain boundary of the material. The peak maximum shifts to higher frequency with an increase in temperature and the broad nature of the peaks indicates the non-Debye nature of Li2SnO3. The activation energy associated with the dielectric relaxation obtained from the electrical impedance spectra is 0.67 eV. From the electric modulus spectra, the activation energies related to conductivity relaxation in the grain and grain boundary of Li2SnO3 are 0.59 and 0.69 eV, respectively. The conductivity–temperature relationship is thermally assisted and obeys the Arrhenius rule with the activation energy of 0.66 eV. The conduction mechanism of Li2SnO3 is via hopping. 相似文献
16.
We have synthesized nanosized La0.67Ca0.33MnO3 by a simple low-cost novel synthesis route without calcination at high temperature. The study of these nanoparticles indicates
excellent properties similar to colossal magnetoresistance (CMR) materials sintered at ∼1600°C for 20 h. The resulting particle
size is in the range of 50–160 nm as determined by scanning electron microscopy. Resistivity measurement has been carried
out down to 12 K. The sample shows metal-to-insulator (M–I) transition at 205 K.
相似文献
17.
The present paper reports the synthesis, crystal structure, 13C and 111Cd cross-polarization magic-angle spinning nuclear magnetic resonance(CP-MAS-NMR) analysis and ac conductivity for a new organic–inorganic hybrid salt, [C7H12N2][CdCl4]. The compound crystallizes in the triclinic system, space group P\( \overline 1 \), with unit cell dimensions: a?=?7.1050(3) Å, b?=?8.9579(3) Å, c?=?9.4482(3) Å, α?=?81.415(1)°, β?=?89.710(2)°, γ?=?85.765(1)°, V?=?592.97(4) Å3, and Z?=?2. The asymmetric unit is composed of one-2,4-diammonium toluene cation and one [CdCl4]2? anion. The Cd atom is in a slightly distorted octahedra coordination environment. Its structure can be described by infinite chains of CdCl6 octahedron linked to organic cations by a strong charge-assisted N–H???Cl interactions in order to build organic–inorganic layers staked along \( \left[ {0\overline 1 1} \right] \) direction. The solid state 13C CP-MAS-NMR spectra has shown seven isotropic resonances, confirming the existence of seven non-equivalent carbon atoms, which is consistent with crystal structure determined by X-ray diffraction. As for 111Cd MAS-NMR, it has shown one cadmium site with isotropic chemical shift observed at 167.2 ppm. The complex impedance of the compound has been investigated in the temperature range of 403–460 K and in the frequency range of 200 Hz–5 MHz. The impedance plots have shown semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance R p and constant phase elements. 相似文献
18.
The Li2BaP2O7 compound has been obtained by the conventional solid-state reaction and characterized by X-ray powder diffraction. The title material crystallizes in the monoclinic system with C2/c space group. Electrical properties of the compound have been studied using complex impedance spectroscopy in the frequency range 200 Hz–5 MHz and temperature range 589–724 K. Temperature dependence of the DC conductivity and modulus was found to obey the Arrhenius law. The obtained values of activation energy are different which confirms that transport in the titled compound is not due to a simple hopping mechanism. AC conductivity measured follows the power-law dependence σ AC?~?ω s typical for charge transport. Therefore, the experimental results are analyzed with various theoretical models. Temperature dependence of the power law exponent s strongly suggests that tunneling of large polarons is the dominant transport process. 相似文献
19.
The electrophysical properties and structure of the nonstoichiometric high-temperature superconductor YBa2Cu3O
y
restored at T = 930–950°C after low-temperature decomposition (T = 200°C) into phases different in the oxygen content have been studied. It has been shown that, unlike heat treatments at
T ≤ 900°C, the superconducting properties are almost completely restored for 3–5 h during grain recrystallization, which is
impossible at lower temperatures. After short-term annealing at T = 930–950°C (for 1–2 h), the ceramic material still contains a significant number of structural defects, most likely, in
cation sublattices. These defects can contribute to the pinning of magnetic vortices, which substantially increases the critical
current density in magnetic fields up to 2 T as compared to ceramic materials produced by the conventional technology. 相似文献
20.
The Rb3(HSeO4)2.5(H2PO4)0.5 compound was prepared and its thermal behavior and electric properties were investigated. The thermogravimetry (TGA) analysis and the differential scanning calorimetric (DSC) show the presence of a structural phase transition of the title compounds at 374 K which is confirmed by the variation of fp and σdc as a function of temperature. The complex impedance of the Rb3(HSeO4)2.5(H2PO4)0.5 compound has been investigated in the temperature range of 295–453 K and in the frequency range 209 Hz–1 MHz. The impedance plots show semicircle arcs at different temperatures, and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance Rp and constant phase elements CPE1 in series with fractal capacity CPE2. The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law. The conductivity dc follows the Arrhenius relation. The near value of activation energies obtained from the analysis of modulus, conductivity data, and circuit equivalent confirm that the transport is through the ion hopping mechanism, dominated by the motion of the H+ proton in the structure of the investigated materials. 相似文献