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1.
Effect of porosity and pore size distribution on the low-frequency dielectric response, in the range 0.01–100 kHz, in sintered
ZrO2—8 mol% Y2O3 ceramic compacts have been investigated. Small-angle neutron scattering (SANS) technique has been employed to obtain the
pore characteristics like pore size distribution, specific surface area etc. It has been observed that the real and the imaginary
parts of the complex dielectric permittivity, for the specimens, depend not only on the porosity but also on the pore size
distribution and pore morphology significantly. Unlike normal Debye relaxation process, where the loss tangent vis-à-vis the
imaginary part of the dielectric constant shows a pronounced peak, in the present case the same increases at lower frequency
region and an anomalous non-Debye type relaxation process manifests. 相似文献
2.
S. A. Gridnev N. A. Tolstykh D. V. Polukhin 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(10):1300-1303
The low-frequency process of dielectric relaxation in the new lead-free compound BiLi0.6W0.4O3 prepared by conventional ceramic technology is studied. The features of dielectric relaxation are discussed in terms of a
model of interaction between the domain boundaries and point defects of a crystalline lattice. 相似文献
3.
V. A. Sandler E. D. Yakushkin 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(9):1245-1248
The dspersion dielectric permeability and ion conductivity of La2Mo2O9 ceramics was studied. It was established that the observed low-frequency dielectric dispersion is due to relaxation effects
related to high ion conductivity. It is shown that the phase transition in La2Mo2O9 has characteristic features of a superionic phase transition. 相似文献
4.
S.K. Rout T. Badapanda E. Sinha S. Panigrahi P.K. Barhai T.P. Sinha 《Applied Physics A: Materials Science & Processing》2008,91(1):101-106
BaTi0.6Zr0.4O3 (BTZ) ceramic was synthesized by a soft chemical route. X-ray diffraction at room temperature shows that the sample has cubic
perovskite structure with space group Pm-3m. Temperature dependent dielectric study of the sample has been investigated in
the frequency range from 50 Hz to 1 MHz. The density of the sample was determined using Archimedes’ principle and found to
be ∼ 97% of the X-ray density. The average grain size in the pallet was found to be ∼ 1 μm. The dielectric constant peaks
at temperature Tm which is dependent on the frequency. The dielectric relaxation rate follows the Vogel–Fulcher relation with activation energy = 0.0185 eV,
and freezing temperature = 186 K. All these measurements confirm that BTZ is a relaxor ferroelectric.
PACS 77.22.Jp; 77.84.-s; 77.80.Bh; 77.22.Gm 相似文献
5.
I.?A.?Santos R.?G.?Mendes J.?A.?Eiras J.?de?Los?S.?Guerra E.?B.?Araújo 《Applied Physics A: Materials Science & Processing》2009,95(3):757-760
The dielectric properties of Sr0.75Ba0.25Nb2O6 relaxor ferroelectric thin films were carefully analyzed. In contrast to bulk samples which present three distinct dielectric
relaxation phenomena Sr0.75Ba0.25Nb2O6 thin films present only two of them. The suppression of the third anomaly can be mainly attributed to the narrow grain size
distribution of nanograins and weak tensile strains imposed to the film from the substrate. The whole set of results point
to the interpretation of a dielectric response characteristic of mesoscopic structure, which is composed of clusters and nanodomains. 相似文献
6.
S. A. Gridnev N. A. Tolstykh N. V. Volodin 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(9):1260-1263
The properties of the new lead-free compound BiLi0.6W0.4O3, obtained using ceramic technology, were studied by dielectric and mechanical spectroscopy. The anomalies of internal friction
are, along with the elastic and dielectric properties observed experimentally at a temperature of 350°C, related to its structural
phase transition. Dielectric and mechanical relaxation due to processes of interaction between crystal lattice defects was
revealed in the low-temperature phase. 相似文献
7.
Y. B. Qin H. X. Yang L. Wang H. F. Tian C. Ma Y. Li H. L. Shi J. Q. Li 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(2):231-236
The structural and physical properties of the layered
Yb2Fe3O7 have been extensively investigated. Transmission
electron microscopy (TEM) observations at room temperature reveal the
presence of diffuse zigzag-type streaks at 1/3(h h l) running along the c*
axis direction, suggesting the presence of a charge ordered state with a
shorter coherence length in comparison with that in Lu2Fe3O7.
The measurements of magnetization demonstrate that the replacement of
Lu3+ by the magnetic Yb3+ ion in this layered system could
result in visible effects on the low-temperature magnetic properties: the
ferrimagnetic phase transition temperature decreases and an additional
magnetic anomaly possibly attributed to antiferromagnetic coupling between
Yb and Fe layers appears at around 50 K. Analysis of the dielectric
properties shows that the Yb2Fe3O7 material in general has a
large dielectric constant of about 5000 at room temperature, and a broader
relaxation time distribution in comparison with ErFe2O4. 相似文献
8.
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
9.
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
10.
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
11.
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
12.
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
13.
Vassiliki Katsika-Tsigourakou Efthimios S. Skordas 《Central European Journal of Physics》2010,8(6):900-904
Various experimental techniques have revealed that the predominant intrinsic point defects in BaF2 are anion Frenkel defects. Their formation, enthalpy and entropy, as well as the corresponding parameters for the fluorine
vacancy and fluorine interstitial motion have been determined. In addition, low temperature dielectric relaxation measurements
in BaF2doped with uranium leads to the parameters τ0, E in the Arrhenius relation τ = τ0 exp(E/k
B
T) for the relaxation time τ. For the relaxation peak associated with a single tetravalent uranium, the migration entropy deduced
from the pre-exponential factor τ0 is smaller than the anion Frenkel defect formation entropy by almost two orders of magnitude. We show that, despite their
great variation, the defect entropies and enthalpies are interconnected through a model based on anharmonic properties of
the bulk material which have been recently studied by employing density-functional theory and density-functional perturbation
theory. 相似文献
14.
PVDF + BaZrO3 electroactive nanocomposite thin film has been prepared by solution casting method. The structural analysis was carried out by using x-ray diffraction pattern and atomic force microscopy (AFM). Generally, the performance of dielectric capacitors toward higher energy density and higher operating temperatures has been drawing increased interest. In this regard, the present study was focussed on the fabrication and characterization of PVDF + BaZrO3 electroactive nanocomposites in view of enhancing the energy density at elevated temperature. Cole-Cole plot is an agreement with multiple relaxation process in electroactive nanocomposites. Dielectric energy storage performance is assessed for PVDF nanocomposites with different wt% of BaZrO3 at different frequencies and temperature. It has been observed that with increase of temperature, the permittivity increased while the energy density slightly decreased but significantly higher than pure polymer PVDF. A high energy density of 6.88 J/cm3 was obtained for BaZrO3 electroactive nanocomposites at 50 °C and 5.06 J/cm3 at 70 °C. Overall, the testing results indicate that using nanocomposites of PVDF and BaZrO3 as a dielectric component is promising for implementation to preserve high energy density values up to temperatures of 70 °C.The enhancement of dielectric permittivity and the energy density is attributed due to increase of interracial charge density. The effect of BaZrO3 nanoparticles in energy density of PVDF is first time reported. 相似文献
15.
A. F. Sadykov Yu. V. Piskunov A. P. Geraschenko V. V. Ogloblichev A. G. Smol’nikov I. Yu. Arapova Z. N. Volkova A. A. Bush 《JETP Letters》2017,105(11):715-720
Comprehensive NMR investigation of low-frequency spin dynamics of LiCu2O2 (LCO) and NaCu2O2 (NCO) low-dimensional helical magnets in the paramagnetic state has been carried out for the first time. Temperature dependences of the spin–lattice relaxation rate and anisotropy on various LCO/NCO nuclei have been determined at various orientations of single crystals in an external magnetic field. The spatial asymmetry of spin fluctuations in LCO multiferroic has been discovered. The quantitative analysis of the anisotropy of spin–lattice relaxation in LCO/NCO has allowed estimating the contributions of individual neighboring Cu2+ ions to the transferred hyperfine field on Li+(Na+) ions. 相似文献
16.
The effect of Ge additive on the physical and dielectric properties of Se75Te25 and Se85Te15 glassy alloys has been investigated. It is inferred that on adding Ge, the physical properties i.e., average coordination number, average number of constraints and average heat of atomization increase but lone pair electrons, fraction of floppy modes, electronegativity, degree of crosslinking and deviation of stoichiometry (R) decrease. The effect of Ge doping on the dielectric properties of the bulk Se75Te25 and Se85Te15 glassy alloys has also been studied in the temperature range 300–350 K for different frequencies (1 kHz–5 MHz). It is found that, with doping, the dielectric constant ε′ and dielectric loss ε″ increase with increase in temperature and decrease with increase in frequency. The role of the third element Ge, as an impurity in the two pure binary Se75Te25 and Se85Te15 glassy alloys has been discussed in terms of the nature of covalent bonding and electronegativity difference between the elements used in making the aforesaid glassy systems. 相似文献
17.
A. A. Bush K. E. Kamentsev M. V. Provotorov T. N. Trushkova 《Physics of the Solid State》2004,46(9):1722-1729
Measurements and analysis of the temperature and frequency dependences of permittivity and losses and of the electrical resistivity of Pb5Ge3O11 ferroelectric crystals at temperatures of 100 to 600 K and frequencies of 0.1 to 100 kHz are reported. The dielectric characteristics of the crystals exhibit, in addition to clearly pronounced anomalies near the Curie point TC=450 K, less distinct anomalous features of the relaxation character in the range 230–260 K. The data obtained on the effect of various factors (degree of crystal polarization, crystal annealing at different temperatures and in different environments, etc.) on the low-temperature anomalies serve as a basis for discussing the possible mechanisms responsible for these anomalies. It is concluded that the low-temperature dielectric anomalies originate from thermal carrier localization in defect levels in the band gap, which entail the formation of local polarized states. 相似文献
18.
S. Wongsaenmai W. Qu S. Ananta R. Yimnirun X. Tan 《Applied Physics A: Materials Science & Processing》2007,88(4):757-761
Ferroelectric ceramics with formula Pb0.8Ba0.2[(In1/2Nb1/2)1-xTix]O3 (PBINT) (x=0.0,0.1,0.2,0.3,0.4 and 0.5) were prepared via a two-step solid state reaction method. It was found that ceramics
with compositions in the range of x=0.0∼0.3 showed a pseudo-cubic structure, whereas the ceramic with x=0.5 displayed a tetragonal
structure. All compositions showed significant frequency dispersion in their dielectric properties. The remanent polarization
Pr as well as the coercive field Ec, measured at room temperature, increases with the Ti content. The experimental results obtained in this system are summarized
into a phase diagram, with the morphotropic phase boundary (MPB) located at x=0.4. Compared with the Pb[(In1/2Nb1/2)1-xTix]O3 solid solution system, incorporating Ba in the A-site leads to a significant decrease in the dielectric maximum temperature
Tmax, a suppression of the dielectric relaxation parameter γ, and a shift of the MPB composition to a higher Ti content.
PACS 77.84.Dy; 77.80.Bh; 77.22.Ch 相似文献
19.
K. Prasad Lily K. Kumari K.P. Chandra K.L. Yadav S. Sen 《Applied Physics A: Materials Science & Processing》2007,88(2):377-383
Polycrystalline (Na0.5Sb0.5)TiO3 was prepared using a high-temperature solid-state reaction method. An XRD analysis indicated the formation of a single-phase
monoclinic structure. Complex impedance studies revealed the presence of grain boundary effects from 300 °C onwards. Also,
the dielectric relaxation in the system was found to be of a non-Debye type. The ac conductivity data were used to evaluate
the density of states at the Fermi level, the minimum hopping length and activation energy of the compound. The dc electrical
and thermal conductivities of grain and grain boundary have been assessed. The correlated barrier hopping model was found
to successfully explain the mechanism of charge transport in (Na0.5Sb0.5)TiO3.
PACS 72.20.Ee; 77.22.Ch; 77.22.Gm; 77.84.Dy; 81.05.Je 相似文献
20.
Kalpana Murugesan Govindan Kadarkarai Selvasekarapandian Subramanian Premalatha Manavalan Senthil Kumar Parthasarathy 《Ionics》2017,23(10):2621-2629
Modified Pechini-type polymerizable precursor method has been used to prepare nanosized Li1-xTbxNiPO4 (x = 0, 0.03, 0.05, and 0.07) solid solutions to obtain homogeneous with controlled stoichiometry and smaller particle size. The reaction temperature was determined by thermogravimetric (TG/DTA) analysis. X-ray diffraction analysis reveals the formation of orthorhombic structure and the calculated crystallite sizes are found to be in the range of 75–89 nm. Morphological, compositional, and vibrational properties were performed by SEM, EDAX, and FTIR, respectively. Conductivity measurements were carried out at room temperature by AC impedance analysis. The Li0.97Tb0.03Ni0.99PO4 sample shows one order of higher conductivity than pure LiNiPO4. Higher concentration of terbium samples such as Li0.95Tb0.05Ni0.99PO4 and Li0.93Tb0.07Ni0.99PO4 lead to decrease of conductivity. The frequency dependency of dielectric permittivity, dielectric loss, and electric modulus of Li1-x TbxNiPO4 solid solutions are studied. The frequency-dependent plot of modulus reveals that the conductivity relaxation is of non-Debye type. 相似文献