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1.
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
2.
M. D. Volnyanskii S. N. Plyaka M. P. Trubitsyn Yahia A. H. Obaidat 《Physics of the Solid State》2012,54(3):499-503
The electrical properties of a lithium heptagermanate (Li2Ge7O15) crystal have been studied in DC and AC measuring fields at temperatures from 500 to 700 K. In a DC field, a substantial
decrease of electrical conductivity σ with time has been detected. On the basis of kinetic dependences σ(t), estimates of the charge carrier diffusion coefficient D have been obtained. In the frequency range 101–105 Hz, the spectra of complex impedance ρ*(f) have been measured. The analysis of diagrams in the complex plane (ρ″–ρ′) has been performed within the equivalent circuit
approach. It has been shown that, in the considered temperature and frequency intervals, the electrical properties of Li2Ge7O15 crystals have been determined by the hopping conduction of interstitial lithium ions A
Li and accumulation of charge carriers near the blocking Pt electrodes. 相似文献
3.
A. I. Burkhanov Yu. V. Kochergin K. Bormanis A. Kalvane 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(9):1264-1266
The dielectric nonlinearity in BaBi2Nb2O9 and SrBi2Ta2O9 layered ceramics was studied by measuring their polarization loops and reverse dependences of permittivity. It was shown
that the features of the dielectric response of BaBi2Nb2O9 and SrBi2Ta2O9 in strong fields can be explained by glass-like properties and the contribution of the domain structure of the ferroelectric
material to repolarization processes, respectively. 相似文献
4.
Deokki Min Nils Hoivik Geir Uri Jensen Frode Tyholdt Camilla Haavik Ulrik Hanke 《Applied Physics A: Materials Science & Processing》2011,105(4):867-874
The dielectric properties of zirconium dioxide (ZrO2) ceramic thin films were characterized up to 50 GHz using coplanar waveguides (CPWs) and metal–insulator–metal (MIM) capacitors
with top circular electrodes. The ZrO2 films were deposited using a chemical solution onto high-resistivity Si wafers and metal layers. The real part of the dielectric
constant of approximately 22 and 26 was extracted at 50 GHz for CPW and MIM structures, respectively, and the loss tangent
was approximately 0.09 at 50 GHz. C–V and I–V measurements were carried out to determine low-frequency and DC dielectric properties. The measurement results indicate that
ZrO2 is a promising material to be used as a dielectric layer for radio-frequency (RF) microelectromechanical systems (MEMS) capacitive
switches. 相似文献
5.
O. A. Karaeva L. N. Korotkov A. A. Naberezhnov E. Rysiakiewicz-Pasek 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(9):1283-1286
The dielectric properties of composite materials prepared by embedding P(VDF60/Tr40) and P(VDF88/Te12) polar copolymers in porous glass matrices with a mean flow-through pore diameter of around 320 nm were investigated in the
temperature range 200–450 K. Strong dielectric relaxation, the characteristic time of which conformed to the Williams-Landel-Ferry
law, was observed in the vicinity of glass transition point T
g
of an amorphous fraction of polymer inclusions. An increase (≈10 K) in the T
g
temperature of the amorphous fraction of incorporated polymeric materials was detected. 相似文献
6.
The optical properties of Fe78Si10B12 ferromagnetic alloy in amorphous, crystalline, and intermediate structural states have been investigated by ellipsometry
in the spectral range of 0.22–18 μm. It is established that alloy crystallization leads to a significant change in the optical
constants and the frequency dependences of the dielectric functions calculated based on these optical constants. The structural
reconstruction under heat treatment leads to an increase in the intensity and shift of interband absorption bands. The plasma
and relaxation frequencies of conduction electrons are determined; their numerical values also depend on the degree of atomic
ordering. 相似文献
7.
A. P. Shamshin 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(9):1252-1254
Temperature dependences of a complex dielectric permittivity of lithium ammonium sulphate LiNH4SO4 monocrystal in a frequency range of 3–26 GHz were studied using technique of the cylindrical slot-hole resonator. It was
shown that obtained dispersion dependences can be described taking in account the normal distribution of relaxation times. 相似文献
8.
Ruiting Sun Xiaoli Wang Jing Shi Le Wang 《Applied Physics A: Materials Science & Processing》2011,104(1):129-133
New perovskite solid solution ceramics of (1−x)BaTiO3-xBi(Mg1/2Ti1/2)O3 ((1−x)BT-xBMT, x≤0.09) were synthesized by the solid-state reaction technique. X-ray diffraction studies have revealed a stable single perovskite
structure for all samples. Dielectric measurements were carried out at different frequencies and temperatures. The polarization
evolutions with temperatures were measured to investigate the ferroelectric properties. All the compositions show features
of ferroelectrics with diffuse phase transition, though the temperature T
m
of their dielectric constant maximum ε
m
is frequency dependent. The dielectric constant peak ε(T) of (1−x)BT-xBMT ceramics become broad with increasing BMT content. During the temperature range of ε(T) peak summit, (1−x)BT-xBMT ceramics present quasi-linear dielectric phenomenon under high electric field with very high dielectric constant. 相似文献
9.
A. U. Sheleg V. G. Hurtavy S. N. Mustafaeva E. M. Kerimova 《Physics of the Solid State》2011,53(3):472-475
The temperature dependences of the electrical conductivity and the permittivity of TlInSe2 and TlGaTe2 crystals unirradiated and irradiated with 4-MeV electrons at a doze of 1016 cm−2 have been investigated. It has been established that electron irradiation leads to a decrease in the electrical conductivity
σ and the permittivity ɛ over the entire temperature range under study (90–320 K). It has been revealed that the TlInSe2 and TlGaTe2 single crystals undergo a sequence of phase transitions characteristic of crystals of this type, which manifest themselves
as anomalies in the temperature dependences σ = f(T) and ɛ = f(T). Electron irradiation at a doze of 1016 cm−2 does not affect the phase transition temperatures of the crystals under investigation. 相似文献
10.
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
11.
The double perovskite Sr2NiMoO6 powders and ceramics were prepared by two different (conventional and precursor) solid-state reaction methods. The phase
structure was characterized by XRD and TEM techniques. It has been indicated that single-phase perovskite powders were obtained
when calcined in air at 1300°C. However, nano-particles of the size 30–60 nm have been found in powders prepared with the
precursor method, while those from the conventional route exhibit large irregular shaped particles with aggregation. The dielectric
properties (ε
r
and tanδ) were also examined in the sintered ceramics. The results showed the transition point at 280°C for conventional route, while
no clear phase change was observed in ceramics from the precursor route. These observations clearly indicate that the different
starting processes affected the phase formation behavior and the electrical properties of Sr2NiMoO6 ceramics. 相似文献
12.
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
13.
The layered LiNi0.5Mn0.47Al0.03O2 was synthesized by wet chemical method and characterized by X-ray diffraction and analysis of magnetic measurements. The
powders adopted the α-NaFeO2 structure. This substitution of Al for Mn promotes the formation of Li(Ni0.472+Ni0.033+Mn0.474+Al0.033+)O2 structures and induces an increase in the average oxidation state of Ni, thereby leading to the shrinkage of the lattice
unit cell. The concentration of antisite defects in which Ni2+ occupies the (3a) Li lattice sites in the Wyckoff notation has been estimated from the ferromagnetic Ni2+(3a)–Mn4+(3b) pairing observed below 140 K. The substitution of 3% Al for Mn reduces the amount of antisite defects from 7% to 6.4–6.5%.
The analysis of the magnetic properties in the paramagnetic phase in the framework of the Curie–Weiss law agrees well with
the combination of Ni2+ (S = 1), Ni3+ (S = 1/2) and Mn4+ (S = 3/2) spin-only values. Delithiation has been made by the use of K2S2O8. According to this process, known to be softer than the electrochemical one, the nickel ions in the (3b) sites are converted into Ni4+ in the high spin configuration, while Ni2+(3a)–Mn4+(3b) ferromagnetic pairs remain, as the Li+(3b) ions linked to the Ni2+(3a) ions in the antisite defects are not removed. The results show that the antisite defect is surrounded by Mn4+ ions, implying the nonuniform distribution of the cations in agreement with previous NMR and neutron experiments. 相似文献
14.
G. A. Komandin A. S. Prokhorov V. I. Torgashev E. S. Zhukova B. P. Gorshunov A. A. Bush 《Physics of the Solid State》2011,53(4):736-744
The spectra of complex permittivity of a Ba2Mg2Fe12O22 single crystal belonging to the family of Y-type hexaferrites have been measured over a wide temperature range (10–300 K) with the aim of determining the dynamic parameters
of the phonon and magnetic subsystems in the terahertz and infrared frequency ranges (3–4500 cm−1). A factor-group analysis of the vibrational modes has been performed, and the results obtained have been compared with the
experimentally observed resonances. The oscillator parameters of all nineteen phonon modes of E
u
symmetry, which are allowed by the symmetry of the Ba2Mg2Fe12O22 crystal lattice, have been calculated. It has been found that, at temperatures below 195 and 50 K, the spectral response
exhibits new absorption lines due to magnetic excitations. 相似文献
15.
A. V. Semirov D. A. Bukreev A. A. Moiseev V. A. Lukshina E. G. Volkova S. O. Volchkov G. V. Kurlyandskaya 《Technical Physics》2011,56(3):395-399
The temperature dependences of the magnetic properties and the magnetoimpedance effect of soft magnetic nanocrystalline Fe73.5Si16.5B6Nb3Cu1 alloy ribbons are studied in the temperature range 24–160°C. A high temperature sensitivity of the impedance and the magnetoimpedance
effect of the ribbons are detected in the ac frequency range 0.1–50 MHz. At an ac frequency of 50 MHz, the change in the impedance
reaches 0.2 Ω/°C (0.5%/°C) in the temperature range 85–160°C. When the temperature increases, a monotonically decreasing character
of the dependence of the magnetoimpedance effect on the applied magnetic field changes into a dependence having an increasing
initial segment. The effect of temperature on the magnetoimpedance properties of the soft magnetic nanocrystalline ribbons
is shown to result from temperature-induced changes in their electrical conductivity, magnetization, and effective magnetic
anisotropy. 相似文献
16.
A. M. Pashaev B. G. Tagiev O. B. Tagiev Kh. B. Ganbarova 《Journal of Applied Spectroscopy》2011,78(2):266-271
We have ground bulk samples to obtain nanoparticles of (Ga2S3)1–x
(Eu2O3)
x
solid solutions, the sizes of which were determined using an atomic force microscope. The photoluminescence spectra of the
nanoparticles were studied in the temperature interval 77–300 K. We have established the mechanisms for emission and transfer
of energy from the matrix to the rare-earth ion, and we determined the Stokes shift (ΔS = 0.7 eV), the Huang–Rhys parameter
(S = 16), and the optical phonon energy (ħ−ω = 23 meV). 相似文献
17.
I. V. Stepanova N. G. Gorashchenko S. V. Krasil’nikov V. B. Tsvetkov 《Optics and Spectroscopy》2011,111(2):230-232
Glasses of 2Bi2O3-3GeO2-xFe2O3 composition, where x = 0–1.5, are obtained under oxidizing and reducing conditions. Glass-ceramic materials are produced by the thermal treatment
of the glasses, the properties of which, as well as those of the original glasses, are studied by the methods of X-ray phase
analysis and optical and luminescent spectroscopy. It is found that the Fe3+/Fe2+ ion ratio in the samples changes depending on the synthesis conditions of the original glasses and crystallization process. 相似文献
18.
M. Aoki K. Miwa T. Noritake N. Ohba M. Matsumoto H.-W. Li Y. Nakamori S. Towata S. Orimo 《Applied Physics A: Materials Science & Processing》2008,92(3):601-605
We have investigated the structural and dehydriding properties of Ca(BH4)2. It was found that Ca(BH4)2 undergoes a structural phase transformation from an orthorhombic low-temperature (LT) modification into a tetragonal high-temperature
(HT) modification between 433 K and 523 K. The amount of hydrogen desorbed from Ca(BH4)2 during the pressure–composition (p–c) isotherm measurement was 5.9 mass%. This hydrogen desorption is caused by the partial dehydrogenation of Ca(BH4)2 accompanied by the formation of CaH2 and orthorhombic intermediate phases. 相似文献
19.
L. N. Korotkov T. N. Korotkova R. R. Levitskii S. I. Sorokov A. S. Vdovych 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(10):1331-1334
The time dependences of polarization of K0.88(NH4)0.12H2PO4 mixed crystal have been studied within the temperature range of 74–100 K. Two mechanisms of polarization relaxation were
found. The first mechanism is caused by domain walls lateral motion and their interaction with point lattice defects. The
second one supposedly is due to polar regions infiltration through the regions of frustrated paraelectric phase. 相似文献
20.
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