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1.
The lead pyrophosphate, Pb2P2O7, compound was prepared by conventional solid-state reaction and identified by X-ray powder diffractometer. Pb2P2O7 has a triclinic structure whose electrical properties were studied using impedance spectroscopy technique. Both impedance
and modulus analysis exhibit the grain and grain boundary contribution to the electrical response of the sample. The temperature
dependence of the bulk and grain boundary conductivity were found to obey the Arrhenius law with activation energies E
g = 0.66 eV and E
gb = 0.67 eV, respectively. The scaling behavior of the imaginary part of the complex impedance suggests that the relaxation
describes the same mechanism at various temperatures. 相似文献
2.
The temperature dependence of the electrical conductivity of the compound 2,4,4-trimethyl-4,5-dihydro-3H-benzo[b] [1,4] diazepin-1-ium tetrachlorocadmiate in the different phases follows the Arrhenius law. The imaginary part of
the permittivity constant is analyzed with the Cole–Cole formalism. In the temperature range 348–394 K, the activation energy
of conductivity obtained from complex permittivity in regions I and II are, respectively, 1.03 and 0.33 eV, and E
m (in regions I and II are, respectively, 0.97 and 0.36 eV) obtained from the modulus spectra is close, suggesting that the
ion transport is probably due to a hopping mechanism. The Kohlrausch–Williams–Watts function,
j(t) = exp( - ( \fractt\textKWW )b ) \varphi (t) = \exp \left( { - {{\left( {\frac{t}{{{\tau_{\text{KWW}}}}}} \right)}^\beta }} \right) , and the coupling model are utilized for analyzing electric modulus at various temperatures. The decreasing of β at 373 K is due to approaching the temperatures of change in the conduction mechanism of the sample. 相似文献
3.
Malgorzata Adamczyk Lucjan Kozielski Dariusz Bochenek Daria Radoszewska Marian Pawełczyk Beata Wodecka-Duś 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(2):37
In recent years a wide range of Aurivillius layered materials have been introduced. These novel materials are produced in many various forms such as fibers, thin films as well as bulk by using a number of processing routes. As advanced materials they are they have many interesting properties which include a number of useful electrical properties related to separated grain and grain boundary conductivity, impedance, activation energies, etc. In this paper these properties are described and discussed in detail. The electrical properties of the vanadium doped BaBi2Nb2O9 ceramic was measured over a wide range of temperatures by impedance spectroscopy (IS). The separated grain activation energy, calculated from Arrhenius characteristics at temperatures between room temperature and 600 °C, was 1 eV for 0 at.% of vanadium dopant and 1.2 eV for 10 at.%, whereas the activation energies in the grain boundary region were 0.97 and 1.15 eV, respectively. The obtained results suggest the significant role of vanadium dopant, causing ordering the crystalline structure. 相似文献
4.
Photoacoustic spectroscopy (PAS) is one of the important branches of spectroscopy, which enables one to detect light-induced
heat production following the absorption of pulsed radiation by the sample. As2S3, As2Se3 and GeSe2 exhibit a wide variety of photo-induced phenomena that enable them to be used as optical imaging or storage medium and various
electronic devices, including electro-optic information storage devices and optical mass memories. Therefore, accurate measurement
of thermal properties of semiconducting films is necessary to study the memory density. The thermal conductivity of thin films
of As2S3 (thickness 100 μm and 80 μm), As2Se3 (thickness 100 μm and 80 μm) and GeSe2 (thickness 120 μm and 100 μm) has been measured using PAS technique. Our result shows that the thermal conductivity of thicker films is larger than the
thinner films. This can be explained by the thermal resistance effect between the film and the surface of the substrate.
相似文献
5.
E. Z. Kuchinskii I. A. Nekrasov Z. V. Pchelkina M. V. Sadovskii 《Journal of Experimental and Theoretical Physics》2007,104(5):792-804
Pseudogap phenomena are observed for the normal underdoped phase of different high-T
c cuprates. Among others, the Bi2Sr2CaCu2O8 − δ (Bi2212) compound is one of the most studied experimentally. To describe the pseudogap regime in Bi2212, we use a novel generalized
ab initio LDA + DMFT + Σk hybrid scheme. This scheme is based on the strategy of one of the most powerful computational tools for real correlated materials:
the local density approximation (LDA) + dynamical mean-field theory (DMFT). Conventional LDA + DMFT equations are here supplied
with an additional (momentum-dependent) self-energy Σk in the spirit of our recently proposed DMFT + Σk approach taking into account pseudogap fluctuations. In the present model, Σk describes nonlocal correlations induced by short-range collective Heisenberg-like antiferromagnetic spin fluctuations. The
effective single-impurity problem of the DMFT is solved by the numerical renormalization group (NRG) method. Material-specific
model parameters for the effective x
2 − y
2 orbital of Cu-3d shell of the Bi2212 compound, e.g., the values of intra-and interlayer hopping integrals between different Cu sites, the
local Coulomb interaction U, and the pseudogap potential Δ were obtained within the LDA and LDA + DMFT schemes. Here, we report
on the theoretical LDA + DMFT + Σk quasiparticle band dispersion and damping, Fermi surface renormalization, momentum anisotropy of (quasi)static scattering,
densities of states, spectral densities, and angular-resolved photoemission (ARPES) spectra, taking into account pseudogap
and bilayer splitting effects for normal (slightly) underdoped Bi2212 (δ = 0.15). We show that LDA + DMFT + Σk successfully describes strong (pseudogap) scattering close to Brillouin zone boundaries. Our calculated LDA + DMFT + Σk Fermi surfaces and ARPES spectra in the presence of pseudogap fluctuations are almost insensitive to the bilayer splitting
strength. However, our LDA-calculated value of bilayer splitting is rather small to describe the experimentally observed peak-dip-hump
structure. The results obtained are in good semiquantitative agreement with various recent ARPES experiments.
The article was submitted by the authors in English. 相似文献
6.
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
7.
Multiple energy scales are detected in measurements of the thermodynamic and transport properties in heavy fermion metals.
We demonstrate that the experimental data on the energy scales can be well described by the scaling behavior of the effective
mass at the fermion condensation quantum phase transition, and show that the dependence of the effective mass on temperature
and applied magnetic fields gives rise to the non-Fermi liquid behavior. Our analysis is placed in the context of recent salient
experimental results. Our calculations of the non-Fermi liquid behavior, of the scales and thermodynamic and transport properties
are in good agreement with the heat capacity, magnetization, longitudinal magnetoresistance and magnetic entropy obtained
in remarkable measurements on the heavy fermion metal YbRh2Si2. 相似文献
8.
N. M. Barbin D. I. Terentiev S. G. Alekseyev 《Journal of Engineering Thermophysics》2011,20(3):308-314
The thermal behavior of Na2CO3+Li2CO3 melt is studied by the method of thermodynamic simulation. The equilibrium compositions of the gas and salt phases are calculated
at different temperatures in the initial argon atmosphere. Basic trends of the variation in the compositions of the melts
and the gas phase above the melts in the presence of carbon are determined. The obtained results characterizing the stability
of carbonate components in the melt are analyzed. 相似文献
9.
K. Wang K.N. Martin C.G. Morrison R.C.C. Ward G.J. Bowden P.A.J. de Groot 《Applied Physics A: Materials Science & Processing》2007,86(3):325-328
Single crystal 400 nm thick Laves phase [20 Å?DyFe2/80 Å?YFe2]40 superlattice have been grown by MBE with a (110) growth direction. VSM measurements performed at room temperature with an applied field range of ±1.2×105 Oe, directed along the [001] direction, reveal a unique single-phase-liked ferrimagnetic behavior. A dominant exchange spring behavior is revealed by MOKE measurement along the [–110] direction. Furthermore, for striped arrays patterned along the [001] direction with height-to-width ratio of 0.05, a shape anisotropy of the order of 104 erg/cm3 is induced, resulting into a pronounced change of coercivity due to the comparable magnitude with intrinsic anisotropies. The results demonstrate the feasibility of engineering both single-phase-liked and exchange-spring magnet behavior in Laves phase epitaxial hard/soft superlattices by patterning. 相似文献
10.
E. S. Mironchuk 《Bulletin of the Lebedev Physics Institute》2010,37(6):180-181
A method for determining the relative concentration of 13C/12C isotopes by the vibrational-rotational spectrum of CO2 molecule absorption in the range near 2 μm was proposed. The use of the entire region of the diode laser tuning (∼7 cm−1) and multivariate linear regression for spectrum approximation allow measurements at atmospheric pressure. The laser frequency
is additionally stabilized by injection current variation. The ultimate sensitivity of the setup, determined by the plot of
the squared Alan variance, is 0.03% for 2-min signal acquisition. The system does not contain elements cooled by liquid nitrogen
and can be used in medical diagnostics. 相似文献
11.
NaNi1.5P2O7 compound was obtained by the classic ceramic method at high temperature and was characterized by XRD. It was found to crystallize in the triclinic symmetry with the P-1 space group. The electrical conductivity and modulus characteristics of the system have been investigated in the temperature and the frequency range 586–723 K and 200 Hz–1 MHz, respectively, by means of impedance spectroscopy. The ac conductivity for grain contribution was interpreted using the universal Jonscher’s power law. The exponent s decreased with increasing temperature revealing that the conduction inside the studied material is insured by the correlated barrier hopping (CBH) model. The conduction mechanism was explained with the help of Elliot’s theory, and the Elliot’s parameters were determined. Thermodynamic parameters such as the free energy for dipole relaxation ΔG, the enthalpy ΔH, and the change in entropy ΔS have been calculated. 相似文献
12.
V. G. Kytin B. M. Bulychev A. V. Krechetov E. A. Konstantinova V. A. Kulbachinskiĭ R. A. Lunin 《Journal of Experimental and Theoretical Physics》2007,105(1):250-252
A series of new heterofullerides with compositions Rb2MC60, K2MC60, and KM2C60 (M = Mg, Be) have been synthesized. Measurements of the temperature dependences of the magnetic susceptibility in the temperature interval from 4.2 to 300 K reveal a superconducting transition in heterofullerides K2MgC60, KMg2C60, K2BeC60, and Rb2BeC60 at temperatures T c = 13–22 K. The electron states with uncompensated spin are studied by the electron paramagnetic resonance technique. The contributions of conduction electrons and localized electrons to the paramagnetic susceptibility are extracted. 相似文献
13.
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
14.
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
15.
Photopyroelectric spectroscopy of Sb<Subscript>2</Subscript>O<Subscript>3</Subscript> - ZnO ceramics
A. Zakaria Z. Rizwan M. Hashim A. Halim Shaari W. Mohmood Mat Yunus 《The European physical journal. Special topics》2008,153(1):33-35
Photopyroelectric spectroscopy is used to study the
band-gap energy of the ceramic (ZnO + xSb2O3), x = 0.1 - 1.5 mol%
and the ceramic (ZnO + 0.4 mol% Bi2O3 + xSb2O3), x = 0 - 1.5 mol% sintered at isothermal temperature, 1280 °C, for 1 and 2 hours. The wavelength of incident light, modulated
at 9 Hz, is kept in the visible range and the photopyroelectric spectrum with
reference to doping level is discussed. The band-gap energy is reduced from
3.2 eV, for pure ZnO, to 2.86, 2.83 eV for the samples without
Bi2O3at 0.1 mol% of Sb2O3 for 1 and 2 hours of
sintering time, respectively. It is reduced to 2.83, 2.80 eV for the samples
with Bi2O3 at 0 mol% of Sb2O3 for 1 and 2 hours of
sintering time, respectively. The steepness factor σA which
characterizes the slop of exponential optical absorption is discussed with
reference to the doping level. The phase constitution is determined by XRD
analysis; microstructure and compositional analysis of the selected areas
are analyzed using SEM and EDX. 相似文献
16.
R. B. Morgunov E. V. Kurganova S. M. Aldoshin N. A. Sanina T. N. Rudneva 《Physics of the Solid State》2007,49(9):1723-1730
The magnetic properties of the binuclear nitrosyl-iron complexes Fe2(SC3H5N2)2(NO)4 are investigated. It is demonstrated that several types of particles, such as dimers with a pair of spins 1/2, dimers with a pair of spins 5/2, and paramagnetic particles with spin 3/2, make a contribution to the magnetic properties of the complexes. A decrease in the temperature below 25 K leads to a change in the shape of the EPR spectra corresponding to these dimers, so that Lorentzian lines (homogeneous broadening) transform into Gaussian lines (inhomogeneous broadening). This is accompanied by a stepwise change in the EPR line width and g factors. The change in the line shape indicates that complexes become asymmetric at low temperatures, possibly, due to the decrease in the spin exchange frequency below the frequency of the microwave field of the spectrometer. 相似文献
17.
18.
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
19.
We report the Fourier transform infrared (FTIR)–Raman spectroscopy study of spinel Li–Fe–Ti–O oxides viz., LiFeTiO4 and Li2FeTiO4 in order to probe structural details such as type of bonding networks viz., octahedral and tetrahedral, and type of different atomic bonds present in those materials. Both the samples were prepared through solid-state reaction route prior to high-energy ball-milling. All the phases prepared through solid-state reaction and ball-milled were probed using X-ray diffraction, field emission scanning electron microscopy, and FTIR–Raman spectroscopy. X-ray diffraction study indicates spinel phase formation with Fd3m space group symmetry for both LiFeTiO4 and Li2FeTiO4. However, pure phase of Li2FeTiO4 was not achieved in these preparation routes, rather mixed phases of Li2FeTiO4 and Fe2TiO4 were achieved. Field emission scanning electron microscopy (FESEM) analysis indicated porous microstructure for LiFeTiO4 while more agglomerated microstructure for Li2FeTiO4. Ball-milling reduces the grain size partly for both the samples. FTIR–Raman spectroscopy indicates the presence of LiO4 tetrahedral, LiO6 and TiO6 octahedral in the spinel network. Presence of Li–Li–O type bonding was also indicated from spectroscopy analysis. Existence of Fe2TiO4 phase with Li2FeTiO4 was also identified from both FTIR and Raman spectrum. Effect of ball-milling on the spectrum has been exhibited by broadening and peak shifting the FTIR–Raman spectrum, arising from the enhanced lattice strain and structural disorder. 相似文献
20.
We have used x-ray photoelectron spectroscopy to investigate the charge state of oxygen found in the basal structural plane
of YBa2Cu3O6+γ.. We have observed a change in this state after thermal treatment, with a transition to the adjacent structural phase region.
We have shown that changes in the charge state of oxygen can be used as an indicator of structural changes occurring in YBa2Cu3O6+δ.. We have found that the rate of structural relaxation yttrium barium cuprate depends on the amount of structural water
it contains.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 195–198, March–April, 2007. 相似文献