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1.
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
2.
The measurements of electrical conductivity (σ) from 300 to 1200 K and dielectric constant (ε′) from 4·2 to 1200 K of A-type Nd2O2 pellets are reported here. Electrical conductivity (σ) data can be explained in terms of impurity. The dielectric constant (ε′) increases slowly up to 500 K as is expected for ionic solids. The increase ofε′ becomes much faster above 500 K, which is attributed to space charge polarization of thermally generated charge carriers. 相似文献
3.
X. G. Tang Q. X. Liu J. Wang H. L. W. Chan 《Applied Physics A: Materials Science & Processing》2009,96(4):945-952
The effect of a dc bias field on the diffuse phase transition and nonlinear dielectric properties of sol-gel derived Ba(Zr0.2Ti0.8)O3 (BZT) ceramics are investigated. Diffuse phase transitions were observed in BZT ceramics and the Curie–Weiss exponent (CWE)
was γ∼2.0. The dielectric constant versus temperature characteristics and the γ in the modified Curie–Weiss law, ε
−1=ε
m
−1[1+(T−T
m
)
γ
/C1](1≤γ≤2), as a function of the dc bias field was obtained for BZT ceramics. The results indicated that γ is a function of dc bias field, and the γ value decreased from 2.04 to 1.73 with dc bias field increasing from 0 to 20 kV/cm. The dielectric constant decreases with
increasing dc bias field, indicating a field-induced phase transition. The dc bias field has a strong effect on the position
of the dielectric peak and affects the magnitude of the dielectric properties over a rather wide temperature range. The peak
temperature of the dielectric loss does not coincide with the dielectric peak and an obvious minimum value for the dielectric
loss at the temperature of the dielectric peaks is observed. At room temperature, 300 K, the high tunability (K=80%), the low loss tangent (≈0.01) and the large FOM (74), clearly imply that these ceramics are promising materials for tunable capacitor-device applications. 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.
We report the experimental high electric field phase diagram of a nematic
liquid crystal which exhibits a large negative dielectric
anisotropy. We measure simultaneously
the birefringence (Δn) and the dielectric constant
(epsilon⊥) at various applied fields as
functions of the
local temperature of an aligned sample. We also measure the higher harmonics of
the electrical response of the
medium. The following experimental results are noted: (i) enhancement
of orientational order parameter
S in the nematic phase due to both
the Kerr effect and quenching of director fluctuations; (ii) enhancement in the paranematic to
nematic transition temperature (TPN) with field; (iii) divergence of the order parameter
susceptibility beyond the tricritical point as measured
by third harmonic electrical signal; (iv) a small second harmonic
electrical signal which also diverges
near TPN, indicating the presence of
polarised domains. Our measurements show that ΔTPN(= TPN(E)-TNI(0))
varies linearly with |E|
whereas the Landau de Gennes theory predicts a dependence on E2. It is argued that the quenching of director fluctuations by the field makes the dominant contribution to all the observations,
including the thermodynamics of the transition. 相似文献
6.
L. Zhang W. Kleemann J. Dec R. Wang M. Itoh 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):163-171
The dielectric permittivity ε′ - i
of SrTi 18O 3 (STO18) is studied under a dc electric field E as a function of the temperature, T. In ε′
vs.
T, a double-peak is found when 0 < E < 30 KV/m. While the peak at high-T is attributed to the smeared ferroelectric phase transition, the low-T one is induced by domain wall motion. The transverse Ising model including an external homogeneous and quenched random-fields
is successfully used to describe both the smeared phase transition and the domain wall response in the low-T domain state. The calculations are in good agreement with the experimental results.
Received 4 January 2002 / Received in final form 25 March 2002 Published online 19 July 2002 相似文献
7.
Summary In the present paper an analysis of the dielectric behaviour and anharmonic contribution to the dielectric constants has been
made of KCl−KBr mixed ionic crystals. The temperature and volume derivatives of static (ε0), electronic (ε∞) dielectric constants and energy gap parameter (E
g) have been calculated using the Szigeti and Havinga and Bosman dielectric theories. The anharmonic contributions have been
estimated in terms of temperature derivatives of dielectric constants at constant volumes. The modified form of Clausius-Mossotti
theory of dielectric polarization has been used for the mixed crystal under study. The calculated quantities have been compared
with the available experimental data. A good agreement has been obtained.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献
8.
M. Paasch M. Winterlich R. Böhmer R. Sonntag G. J. McIntyre A. Loidl 《Zeitschrift für Physik B Condensed Matter》1995,99(1):333-338
The χ,T phase diagram of (NH4I)x(KI)1−x has been determined using neutron diffraction experiments and dielectric spectroscopy. At low temperatures and with decreasing
χ, the sequence γ, β, ε and glass phase has been detected. The critical concentration χc≈0.55 separates the glassy phase with frozen-in orientational disorder from the ε phase which reveals long-range orientational
order. Close to χc our experiments reveal evidence for two subsequent glass transitions. 相似文献
9.
R. Yimnirun X. Tan S. Ananta S. Wongsaenmai 《Applied Physics A: Materials Science & Processing》2007,88(2):323-328
In this study, lead indium niobate (Pb(In1/2Nb1/2)O3 or PIN) ceramics were prepared by a wolframite precursor method via a vibro-milling technique. Fine-grain ceramics were achieved
with average grain size of 1–2 μm, indicating advantage of the vibro-milling technique used. The dielectric and ferroelectric
properties were measured by means of an automated dielectric measurement set-up and a standardized ferroelectric tester, respectively.
The dielectric properties of PIN ceramic were measured as functions of both temperature and frequency. The results indicated
that the dielectric properties of the PIN ceramic were of relaxor ferroelectric behavior with temperature of dielectric maximum
(Tm)∼53 °C and dielectric constant (εr)∼4300 (at 1 kHz). The P–E hysteresis loop measurements at various temperatures showed that the ferroelectric properties of
the PIN ceramic changed from the paraelectric behavior at temperature above Tm to slim-loop type relaxor behavior at temperature slightly below Tm. Moreover, the P–E loop became more open at temperatures much lower than Tm.
PACS 77.22.Ch; 77.84.Dy 相似文献
10.
R. M. A. Azzam 《Applied Physics A: Materials Science & Processing》1979,20(2):193-195
A new angle of incidence of significance, when considering the reflection of electromagnetic waves at interfaces between transparent
media, is defined. At this angle, denoted by φe, the reflection coefficient of parallel-polarized radiation is equal in magnitude and opposite in sign to the reflection
coefficient at normal incidence. No similar angle exists for the perpendicular polarization. If ε is the relative dielectric
constant, i.e., the ratio of the dielectric constant of the medium of refraction to that of the medium of incidence, we find
that tan φe=(ε2+ε)1/2. Measurement of φe, by equalization of the absolute (intensity) reflectances at normal and oblique incidence, allows ε to be determined using
the inverse relation ε=(tan2φe+1/4)1/2−1/2. 相似文献
11.
H. Lehmann G. Nimtz L. D. Haas T. Jakobus 《Applied Physics A: Materials Science & Processing》1981,25(3):291-295
The dielectric properties of epitaxial Pb1−x
Sn
x
Te layers are investigated at 9 GHz in a composition range betweenx=0 and 0.225. The samples are characterized by fairly low carrier concentrations between 1.4×1016 and 32×1016 cm−3. Data of the static dielectric constant (ε
s
) are obtained at temperatures of 77 and 300 K. The results of ε
s
are 25% to 100% higher compared to previous measurements in bulk material from other authors. The observed higher values
of ε
s
in the investigated samples may be due to the reduced number of point defects in epitaxially grown Pb1−x
Sn
x
Te layers. The model of Kawamura which predicts a dependence of ε
s
on the effective band gap cannot be verified. 相似文献
12.
The principal dielectric constants of the pentyl to octyl derivatives of 4′-n-alkyl-4-cyanobiphenyl have been measured as functions of temperature in their nematic and isotropic phases. All the compounds
exhibit a strong positive dielectric anisotropy due to the presence of a large dipole moment along the major molecular axis.
The principal dielectric constantsε
‖ andε
⊥ as well as the anisotropy Δε decrease with increasing alkyl chain length. The experimental value of
(ε‖+2ε⊥) decreases with decreasing temperature, and is throughout less than the extrapolated isotropic value, in conformity with
the model of antiferroelectric short range order proposed by Madhusudana and Chandrasekhar. 相似文献
13.
Laijun Liu Yanmin Huang Congxue Su Liang Fang Meixia Wu Changzheng Hu Huiqing Fan 《Applied Physics A: Materials Science & Processing》2011,104(4):1047-1051
Sodium potassium niobate K0.5Na0.5NbO3(KNN) ceramic was synthesized by a solid-state technique. The X-ray diffraction of the sample at room temperature showed a
monoclinic phase. The real part (ε′) and imaginary part (ε″) of dielectric permittivity of the sample were measured in a frequency range from 40 Hz to 1 MHz and in a temperature range
from 350 to 850 K. The ε′ deviated from Curie–Weiss law above 702 K, due to additional dielectric contributions resulting from universal dielectric
response and thermally activated space charges at high temperatures. This anomaly arose from a Debye dielectric dispersion
that slowed down following an Arrhenius law. We have established a link between the dielectric relaxation and the conductivity. 相似文献
14.
Rare earth element substituted bismuth ferrites (BiFeO3) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi
x
La1−x
FeO3 (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of
these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz
to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz).
All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature
shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds
to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity
as well as ε′ are found to be maximum for the sample x=0.2 at room temperature. 相似文献
15.
Summary The direct-current resistivity, β, and Hall coefficient,R
H, of lightly dopedn-type InP samples were measured at temperatures (T) down to 12K and magnetic fields up to 4.8 kG. A sharp exponential increase in β, asT was decreased, was observed for temperatures below 80 K. The Hall coefficient showed a similar trend,i.e. R
H increased sharply asT was reduced below 80 K. This is attributed to the freeze-out of conduction electrons onto their donor sites. The donor activation
energy,E
d, calculated from the temperature dependence of the resistivity, was less than the theoretical prediction. An enhanced dielectric
constant would be a possible candidate for such behaviour. The initial decrease in β (asT is reduced) recorded in the higher-temperature region is due to impurity scattering probably combined with lattice scattering.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
16.
A. I. Burkhanov K. P. Guzhakovskaya L. I. Ivleva 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(10):1399-1402
The dielectric nonlinearity in an SBN-75 single crystal doped with 0.01 at % Cr was investigated in the vicinity of a diffuse
phase transition by studying the reverse dielectric dependences ε′(E
=). The influence of illumination and exposure (aging) on the behavior of ε′(E
=) was demonstrated. A reduction in the dielectric memory effect after sample illumination was detected. 相似文献
17.
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
18.
W. Wonneberger F. Gleisberg W. Hontscha 《Zeitschrift für Physik B Condensed Matter》1987,69(2-3):339-345
Using Feigel'man's method in the theory of one-dimensional random systems we have evaluated analytically the depinning electric fieldE
T
and the static dielectric constant 0 for the Fukuyama-Lee-Rice hamiltonian in the weak pinning limit and for low temperatures. This is accomplished by solving a Fokker-Planck equation for finitedc electric fields in order to determine the field dependent pinning energy. The dielectric constant is found to remain independent of the electric field up to the threshold. The product 0
E
T
is also evaluated and compared with other theories. 相似文献
19.
C. Fanggao G. A. Saunders E. F. Lambson R. N. Hampton G. Carini A. Bartolotta M. Lanza 《Il Nuovo Cimento D》1994,16(7):855-864
Summary Electrical-impedance measurements have been made in the frequency range 5 Hz to10 MHz in pure poly(ethylene oxide) having
a molecular weight of 600 000 from 254 K nearly up to the melting point of the crystalline phase (about 330 K). As the temperature
approaches the melting point there are large increases in the realε′ and imaginaryε″ parts of the dielectric constant. The frequency dependence ofε′ is characterized by a primary-relaxation process, whose frequency increases with increasing temperature as a consequence
of decrease of the average structural relaxation time. There is strong evidence that this low-frequency dispersion rises mainly
from the diffusive transport of localised charge carriers rather than a purely orientation relaxation process. In addition
the effects of hydrostatic pressure (0–25 Gpa) on the frequency dependences of the realε′ and imaginaryε″ parts of the dielectric constant have been measured in the same temperature range.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
20.
Observation of relaxation modes in room temperature ferroelectric liquid crystal mixtures 总被引:1,自引:0,他引:1
The dielectric measurements in SmC* and SmA phases of a room temperature ferroelectric liquid crystal mixture FLC-6980 in
the cells of different thickness in planer alignment have been carried out in the frequency range 100 Hz to 1 MHz. A relaxation
mode (called NRM) whose dielectric increment is less than the Goldstone mode has been observed in the SmC* phase. This mode
appears due to the surface effect. Goldstone mode and the soft mode was observable in the vicinity of SmC*-SmA transition
temperature (T
C*A). The dielectric parameters of the Goldstone mode, new mode and the soft mode have been studied as a function of frequency
and temperature. The calculated values for fNRM, δεNRM and distribution parameter αNRM are found to be 325 kHz, 6 and 0.156 for 5μm thick planer cell at 37°C. It is seen that in the vicinity of theT
C*A, soft mode obeys the Curie-Weiss law given by mean field theory. The results have been compared with materials of large spontaneous
polarization. 相似文献