共查询到20条相似文献,搜索用时 15 毫秒
1.
A. U. Sheleg K. V. Iodkovskaya S. V. Rodin V. A. Aliev 《Physics of the Solid State》1997,39(6):975-977
The influence of γ irradiation on the electrical conductivity σ, the dielectric permittivity ɛ, and the dielectric loss tangent tanδ of β-TlInS2 crystals is investigated in the temperature range of the incommensurate phase. It is established that γ irradiation lowers the values of ɛ and tanδ over the entire investigated temperature range and decreases the maxima of the σ(T) and tanδ(T) curves in the vicinity of the transition temperature T
c, but does not alter the transition temperature.
Fiz. Tverd. Tela (St. Petersburg) 39, 1088–1090 (May 1997) 相似文献
2.
The dielectric properties of the ceramics of (1 − x)BiFeO3 − x(KBi)1/2TiO3 (0.40 < x < 0.85) solid solutions with an orthorhombic structure have been studied using impedance spectroscopy in the frequency range
25–106 Hz at different temperatures. It has been shown that these solid solutions undergo a diffuse ferroelectric phase transition.
The Curie temperature is found to be in the range 620–640 K. The activation energies of dielectric polarization relaxation
(δE
M
) and dc charge carriers (ΔE
dc) are determined. It has been established that, in the vicinity of 460 K, ΔE
dc increases jumpwise as the temperature increases. 相似文献
3.
Rajesh Kumar S. Asad Ali Udayan De D. K. Avasthi Rajendra Prasad 《Indian Journal of Physics》2009,83(7):963-968
The passage of heavy ions in a track detector polymeric material produces lattice deformations. These deformations may be
in the form of latent tracks or may vanish by self annealing in time. Heavy ion irradiation produces modifications in polymers
in their relevant electrical, chemical and optical properties in the form of rearrangement of bonding, cross-linking, chain
scission, formation of carbon rich clusters and changes in dielectric properties etc. Modification depends on the ion, its energy and fluence and the polymeric material. In the present work, a study of the dielectric
response of pristine and heavy ion irradiated Makrofol-KG polycarbonate is carried out. 40 μm thick Makrofol-KG polycarbonate
films were irradiated to various fluences with Si8+ ions of 100 MeV energy from Pelletron at Inter University Accelerator Centre (IUAC), New Delhi and Ne6+ ions of 145 MeV from Variable Energy Cyclotron Centre, Kolkata. On irradiation with heavy ions dielectric constant (ɛ′) decreases with frequency where ɛ′ increases with fluence for both the ions. Variation of loss factor (tan δ) with frequency for pristine and irradiated with Si ions reveals that tan δ increases as the frequency increases. Tan δ also increases with fluence. While Ne irradiated samples tan δ shows slight variation with frequency as well as with fluence. Tan δ has positive values indicating the dominance of inductive behavior.
相似文献
4.
B. Lalevic N. Fuschillo B. Kuliyev W. Wang 《Applied Physics A: Materials Science & Processing》1974,5(2):127-132
Transport and dielectric properties of polycrystalline CoO films were studied as functions of the applied field, frequency
and temperature. TheI–V plots showed that the Poole-Frenkel field emission mechanism is responsible for conduction at fields>105 V/cm. The ac conductivity σ(ω), the imaginary part of the dielectric constantε
2, and tan δ plots as functions of frequency revealed three dispersion regions. The σ(ω) andε
2 frequency dependence indicates a non-adiabatic hopping of charge carriers at low frequencies and adiabatic hopping at high
frequencies. The activation energy of a dielectric oscillator is 0.15 eV.
Work supported by the Office of Naval Research. 相似文献
5.
The polycrystalline samples of Pb(Li1/4Dy1/4W1/2)O3 have been synthesized by high-temperature solid-state reaction techniques. Room temperature X-ray diffraction (XRD) studies
of the compound provided preliminary structural data, and hence formation of a single phase desired material was confirmed.
Detailed studies of dielectric constant (ε) and loss (tanδ) as a function of frequency (100 Hz to 10 kHz) at room temperature (298 K) and also as a function of temperature (liquid
nitrogen to 403 K) at 10 kHz suggest that the compound undergoes a ferroelectric phase transition of diffuse type. 相似文献
6.
Triglycine sulfate (TGS) films have been prepared by evaporation from a saturated aqueous solution on substrates of fused
quartz coated by a layer of thermally deposited aluminum (Al/SiO2) and white sapphire (α-Al2O3) on whose surface interdigital electrodes have been deposited by photolithography. The TGS films have a polycrystalline structure
made up of blocks measuring 0.1–0.3 mm (Al/SiO2) and 0.1 × 1.0 mm (α-Al2O3). The polar axis in the blocks is mostly confined to the substrate plane. The temperature dependences of the capacitance
and dielectric losses normal to and in the film plane have maxima at the temperature coinciding with that of the ferroelectric
phase transition in a bulk crystal, T
c
. The low-frequency conductivity G in TGS/Al/SiO2 structures displays a frequency dispersion described by the relation G ∼ ω
s
(s ≈ 0.82). The conduction can be tentatively ascribed to the hopping mechanism involving localized carriers with a ground state
energy of 0.8–0.9 eV. At temperatures above and below T
c
, the low-frequency conductivity in TGS/α-Al2O3 films operates through a thermally-activated mechanism with an activation energy of 0.9–1.0 eV. At the phase transition,
an additional contribution to conductivity appears in TGS/α-Al2O3 films with a dispersion G ∼ ω0.5, which can be associated with domain-wall relaxation. 相似文献
7.
In this letter, we investigate the influence of the stress on magnetoelectric (ME) effect in a magnetostrictive-PZT bilayer.
ME voltage coefficient α*E = δE / δH, where δE is the induced electric field for an applied alternating current (ac) magnetic field δH, is obtained by solving the stress-related piezoelectric constitutive equation and the conventional magnetostrictive equation
with appropriate boundary condition. Based on the free-energy density function of the PZT film in stress state, we get the
stress-related piezoelectric charge coefficient p
d*31 and dielectric permittivity pε*33. After taking the cobalt ferrite (CFO) as magnetostrictive phase, it is found that α*E increases with decreasing 2-d compressive stress for CFO-PZT, which not only is qualitatively consistent with previous experimental
measurements, but also provides a possible route to improve the ME effect.
相似文献
8.
S.U. Adikary A.L. Ding H.L.W. Chan 《Applied Physics A: Materials Science & Processing》2002,75(5):597-600
BaxSr1-xTiO3 thin films with a compositional gradient of x=0.3 to 1 (in 0.1 mole fraction increments) were fabricated on Pt/Ti/SiO2/Si substrates using a modified sol–gel technique. The graded film crystallised in a perovskite structure and consists of
a uniform microstructure with comparatively larger grains. The room-temperature relative dielectric constant (εr) and dielectric loss (cosδ) at 100 kHz were found to be 305 and 0.03 respectively. Dielectric peaks were not observed in
the temperature range from -20 °C to 120 °C. The dielectric constant and dielectric loss were almost independent of temperature.
Polarisation–electric field measurements at room temperature revealed a saturated but slim hysteresis loop with a remanent
polarisation (Pr) of 0.6 μC/cm2 and a coercive field (Ec) of 2.4 kV/mm. The graded film behaves as a stack of BaxSr1-xTiO3 capacitors connected in series and hence the dielectric Curie peaks are removed.
Received: 4 October 2001 / Accepted: 17 October 2001 / Published online: 23 January 2002 相似文献
9.
R. Rianyoi R. Potong N. Jaitanong R. Yimnirun A. Chaipanich 《Applied Physics A: Materials Science & Processing》2011,104(2):661-666
In this work, barium titanate (BT) and cement composites of 0-3 connectivity were produced with BT concentrations of 30%,
50% and 70% by volume using the mixing and pressing method. The dielectric constant (ε
r
) and the dielectric loss (tan δ) at room temperature and at various frequencies (0.1–20 kHz) of the ferroelectric BT-Portland cement composites with different
BT concentrations were investigated. The results show that the dielectric constant of BT-PC composites was found to increase
as BT concentration increases, and that the highest value for ε
r
—of 436—was obtained for a BT concentration of 70%. In addition, the dielectric loss tangent decreased with increasing BT
concentration. Moreover, several mathematical models were used; the experimental values of the dielectric constants are closest
to those calculated from the cube model. The 0-3 cement-based piezoelectric composites show typical ferroelectric hysteresis
loops at room temperature. The instantaneous remnant polarization (P
ir
), at an applied external electrical field (E
0) of 20 kV/cm (90 Hz) of 70% barium titanate composite, was found to have a value ≈3.42 μC/cm2. Furthermore, the piezoelectric coefficient (d
33) was also found to increase as BT concentration increases, as expected. The highest value for d
33 was 16 pC/N for 70% BT composite. 相似文献
10.
The effect of γ irradiation on the temperature hysteresis in dielectric permittivity ɛ and loss tangent tan δ of crystalline Rb2ZnBr4 has been studied in the vicinity of the incommensurate-commensurate phase transition. The ɛ(T) and tan δ(T) curves were found to exhibit anomalies in the form of maxima. Hysteresis was observed in the measured properties, including
the transition temperature T
c
(ΔT=T
c
h
−T
c
c
), in both unirradiated and irradiated samples. It is shown that, as the radiation dose increases the extent of the hysteresis
ΔT increases, the values of ɛ
max and tan δ
max at the transition point decrease, and the anomalies wash out.
Fiz. Tverd. Tela (St. Petersburg) 40, 1911–1914 (October 1998) 相似文献
11.
The complex permittivity (ɛ = ɛ′ − iɛ″) of natural, modified, and irradiated zeolites as a function of the frequency of a variable electric field is measured.
For Ba2+-modified (doped) zeolite, the permittivity and dielectric loss tangent (tanδ) as functions of the electric field frequency
are found to decrease monotonically. When the irradiation dose rises to 105 cm−2, the dielectric loss tangent reaches a maximum and then, starting from a dose of 3 × 1016 cm−2, sharply drops. Such behavior of tanδ is assumed to be associated with Ba2+- and irradiation-induced structural modifications in the unit cell of zeolite. 相似文献
12.
S. O. Gladkov 《Technical Physics》1999,44(3):291-294
It is predicted that at room temperatures a hopping mechanism of charge transfer plays a very important role and leads to
temperature oscillations of the conductivity σ(T) of a dielectric composite. The dependence of the conductivity σ(ω) on the frequency of an alternating electric field is calculated. The relation obtained can be used to determine, first,
the electron relaxation times and, second, and more importantly, the frequency of electron tunneling through the dielectric
matrix from measurements of the conductivity in various frequency ranges.
Zh. Tekh. Fiz. 69, 31–34 (March 1999) 相似文献
13.
CoFe2O4-BaTiO3 composites were prepared using conventional ceramic double sintering process with various compositions. Presence of two phases
in the composites was confirmed using X-ray diffraction. The dc resistivity and thermoemf as a function of temperature in
the temperature range 300 K to 600 K were measured. Variation of dielectric constant (ɛ′) with frequency in the range 100 Hz to 1 MHz and also with temperature at a fixed frequency of 1 kHz was studied. The ac
conductivity was derived from dielectric constant (ɛ′) and loss tangent (tan δ). The nature of conduction is discussed on the basis of small polaron hopping model. The static value of magnetoelectric
conversion factor has been studied as a function of magnetic field. 相似文献
14.
Fourier transform infrared spectroscopy studies have been conducted to investigate the interaction among components in a system
of high molecular weight polyvinylchloride (PVC)–lithium trifluoromethanesulfonate (LiCF3SO3) incorporated with different type of plasticizers, namely, ethylene carbonate (EC), propylene carbonate (PC), and dibutylphthalate
(DBP). Interaction between PVC and LiCF3SO3 was confirmed by C–H rocking mode at 1,255 cm−1 for PVC shift to 1,252 cm−1 in PVC–LiCF3SO3. The plasticizers’ carbonyl (C=O) oxygen atom which carries lone pair electrons interact with Li+ of LiCF3SO3 and methine hydrogen of PVC in LiCF3SO3–plasticizer system and PVC–plasticizer system, respectively. Changes in peaks assigned to 1,264 cm−1 (ν
as(SO3)), 1,033 cm−1 (ν
s(SO3)), 1,181 cm−1 (ν
as(CF3)), 1,230 cm−1 (ν
s(CF3)), 765 cm−1 (δ
s(CF3)), 644 cm−1 (δ
s(SO3)), 578 cm−1 (δ
as(CF3)), and 519 cm−1 (δ
as(SO3)) indicate the occurrence of complexation in the PVC–LiCF3SO3 system, LiCF3SO3–plasticizer system, and PVC–LiCF3SO3–plasticizer system. 相似文献
15.
The relaxor ferroelectric lead iron tantalate, Pb(Fe0.5Ta0.5)O3 (PFT) is synthesized by Coulombite precursor method. The X-ray diffraction pattern of the sample at room temperature shows
a cubic phase. The field dependence of dielectric response is measured in a frequency range 0.1 kHz — 1 MHz and in a temperature
range from 173–373 K. The temperature dependence of permittivity (ɛ′) shows broad maxima at various frequencies. The frequency dependence of the permittivity maximum temperature (T
m
) has been modelled using Vogel-Fulcher relation.
相似文献
16.
CdS nanoparticles have been synthesized by a chemical reaction route using thiophenol as a capping agent. The frequency-dependent
dielectric dispersion of cadmium sulphide (CdS) is investigated in the temperature range of 303-413 K and in a frequency range
of 50 Hz-1 MHz by impedance spectroscopy. An analysis of the complex permittivity (ɛ′ and ɛ″) and loss tangent (tan δ) with frequency is performed by assuming a distribution of relaxation times. The scaling behaviour of dielectric loss spectra
suggests that the relaxation describes the same mechanism at various temperatures. The frequency-dependent electrical data
are analysed in the framework of conductivity and modulus formalisms. The frequency-dependent conductivity spectra obey the
power law. 相似文献
17.
C. Benjamin 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(3):403-410
Reflectance measurements from p-type GaSb:Zn epitaxial films with different hole concentrations (1017–1018 cm-3) have been investigated over the frequency region of
100–1000 cm-1. A minimum broadening feature corresponding to the hole plasmon was observed in the reflectance spectra. The experimental
infrared spectra were well fitted using a
Lorentz-Drude dispersion model. The real part ε1 of the dielectric function decreases with increasing hole concentration. However, the imaginary part ε2
increases with hole concentration in the far-infrared region.
This indicates that the acoustic- and optic-phonons mainly
participate in the free carrier absorption processes. The hole
mobility obtained from Hall-effect measurements is slightly
larger than that derived from optical measurements and the
average ratio of mobilities is estimated to be 1.33. Owing to
overdamping effects, the upper branch of longitudinal-optical
phonon plasmon (LPP) coupled modes was observed. The upper
LPP+ frequency increases with hole concentration and it
shows a transition from phonon-like to plasmon-like behavior. A
theoretical analysis with solutions in the complex frequency
plane describes these experimental results. 相似文献
18.
The effect of gamma irradiation on the dielectric properties and ac conductivity of a TlInS2 single crystal with a layered structure has been investigated in the frequency range from 5 × 104 to 3.5 × 107Hz. It has been shown that gamma irradiation of the TlInS2 single crystal with a dose of 104–2.25 × 106 rad leads to a considerable increase in the dielectric loss tangent tanδ, the real part ɛ′ and imaginary part ɛ″ of the complex
permittivity, and the ac conductivity σ
ac
across the layers. It has been established that, for all gamma irradiation doses, the TlInS2 single crystal is characterized by the dielectric loss due to electrical conduction up to a frequency of 107 Hz and by the relaxation loss at a higher frequency. Irradiation of the TlInS2 single crystal results in an increase in the dispersion of tan δ, ɛ′, and ɛ″. It has been demonstrated that, as the gamma
irradiation dose is accumulated in the TlInS2 single crystal, the density of localized states near the Fermi level N
F increases (from 5.2 × 1018 to 1.9 × 1019 eV−1 cm−3). 相似文献
19.
Silicon diodes with a p
+-n junction made in a 48-μm-thick phosphorus-doped silicon epilayer (resistivity ρ = 30 Ω cm) grown on antimony-doped Si(111)
wafers (ρ = 0.01 Ω cm) are studied. The diodes are irradiated by high-energy (3.5 MeV) electrons with fluences from 5 × 1015 to 2 × 1016 cm−2. It is shown that the conventional equivalent circuit of the diode that consists of a parallel RC network and a series-connected resistor inadequately describes the dependence of the dielectric loss tanδ on variable current
frequency f in the range 1 × 102–3 × 107 Hz. Another equivalent circuit is suggested that includes not only the capacitance and resistance of the n-base (the latter increases because radiation-induced defects are compensated for by shallow donors) but also the f dependence of the capacitance of the space-charge region, which is due to retarded charge exchange between deep-level radiation-induced
defects. 相似文献
20.
Ashok Kumar Baral V. Sankaranarayanan 《Applied Physics A: Materials Science & Processing》2010,98(2):367-373
The nanocrystalline material of 15 mol% Gd-doped ceria (Ce0.85Gd0.15O2−δ
) was prepared by citrate auto ignition method. The electrical study and dielectric relaxation technique were applied to investigate
the ionic transport process in this nanocrystalline material with an average grain size of 13 nm and the dynamic relaxation
parameters are deduced in the temperature range of 300–600°C. The ionic transference number in the material is found to be
0.85 at 500°C at ambient conditions. The oxygen ionic conduction in the nanocrystalline Ce0.85Gd0.15O2−δ
material follows the hopping mechanism. The grain boundary relaxation is found to be associated with migration of charge
carriers. The frequency spectra of modulus M″ exhibited a dielectric relaxation peak corresponding to defect associates
(Gd-Vo\blacksquare \blacksquare)\blacksquare(\mathrm{Gd}\mbox{-}\mathrm{V}_{\mathrm{o}}^{_{_{{\blacksquare\,\blacksquare}}}})^{_{_{{\blacksquare}}}}. The material exhibits very low values of migration energy and association energy of the oxygen vacancies in the long-range
motion, i.e., 0.84 and 0.07 eV, respectively. 相似文献