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1.
Dielectric properties andI–V characteristics of solution-gas interface-formed PbS thin-film capacitors (Al/PbS/Al) of various thicknesses have been studied
in the frequency range 10-106 Hz at various temperatures (300–443 K). Current-voltage (I–V) characteristics show space-charge-limited conduction. Dielectric constant (ε) increases with increasing film thickness and temperature and decreases with increase of frequency. The loss factor (tanδ) peaks observed in tanδ vs frequency and tanδ vs temperature reveal relaxation effect from dipolar orientation. These maxima shift to higher-temperature region with increasing
frequency. The large increase in capacitance (C) and dielectric constant (ε) towards low-frequency (f) region indicates the possibility of an interfacial polarization mechanism in this region. 相似文献
2.
Dongyun Guo Takashi Goto Chuanbin Wang Qiang Shen Lianmeng Zhang 《Journal of Materials Science: Materials in Electronics》2012,23(4):897-900
BaTi4O9 film was prepared on Pt/Ti/SiO2/Si substrate by laser chemical vapor deposition. The microstructure and dielectric properties were investigated. The single-phase
BaTi4O9 film with random orientation was obtained. The surface consisted of round and rectangular grains, and the cross-section was
columnar microstructure. The deposition rate (R
dep) was 135 μm h−1. The dielectric constant (ε
r) and loss (tanδ) were 35 and 0.01, respectively, at 1 MHz. With increasing temperature, ε
r increased and showed a broad peak around 736 K, which indicated there might be a phase transition. 相似文献
3.
Xiaohua Zhou Bo Li Shuren Zhang Haiyan Ning 《Journal of Materials Science: Materials in Electronics》2009,20(3):262-266
CaO–B2O3–SiO2 glass-ceramics were synthesized by sol–gel method, and the effect of Ca/Si ratio on the microstructures, electrical properties
and mechanical characteristics of this ternary system was investigated. The results showed that the increase of CaO content
is favorable for the crystallization of CaO–B2O3–SiO2 system and formation of the desired glass-ceramics. The bending strength of the sintered glass-ceramics increases with CaO
content by increasing of crystalline phases. When the Ca/Si ratio increases, the dielectric constant (ε
r) decreases and loss (tanδ) increases gradually. The thermal expansion coefficient (TEC) enhances by increasing CaO contents due to the formation of
other crystal phases with large TEC value. The glass-ceramics exhibit low dielectric constant and loss (ε
r < 4.7, tanδ < 5 × 10-4 at 1 MHz), high resistivity (ρ > 1012 Ω · cm), as well as excellent mechanical properties (σ ≈ 160 MPa, α ≈ 3.6 × 10−6/°C). 相似文献
4.
Frequency and temperature dependence of dielectric constant (εr), dielectric loss (tanδ), ac conductivity (σac) and complex impedance spectroscopy studies on cured polyester matrix and sisal fibre-reinforced polyester composites (SFRPC)
have been investigated in the frequency range from 180 Hz to 1 MHz and temperature range from room temperature to 200 °C.
The experimental results showed that with the incorporation of sisal fibre, the values of εr, tanδ and σac are increased. It is also found that the values of εr and tanδ for both cured polyester matrix and SFRPC are decreased with increasing frequency, which indicates that the major
contribution to the polarization may come from orientation polarization and interfacial polarization. The increasing value
of εr with increasing temperature at a particular frequency is due to free motion of the dipole molecular chains within the cured
polyester matrix and SFRPC at higher temperature. 相似文献
5.
Results of dielectric and conduction properties of vacuum evaporated tellurium (Te) thin film capacitors (Al-Te-Al) have been
reported in the frequency range 1–100 kHz at various temperatures (303–423 K). Loss factor (tanδ) which shows a maximum with frequency increases with rise of temperature and tanδ
max shift towards high frequency region. The large values of capacitance and dielectric constant (ɛ′) in the low frequency region indicate the possibility of an interfacial polarization mechanism.I-V characteristics show ohmic, space charge limited (SCLC) and thermionic emission conduction mechanisms to operate at low,
intermediate and high voltages respectively. Various transport parameters have been calculated. It has been observed that
the Schottky type of conduction is predominant in the high field region and the Schottky barrier height has been determined.
The Hall coefficient, Hall mobility and carrier concentration are also discussed. 相似文献
6.
J.?S.?Almeida T.?S.?M.?Fernandes A.?J.?M.?Sales M.?A.?S.?Silva G.?F.?M.?P.?Júnior H.?O.?Rodrigues A.?S.?B.?Sombra
In this paper, the structural and dielectric properties of BNO (BiNbO4) was investigated as a function of the external RF frequency and temperature. The BNO Ceramics, prepared by the conventional
mixed oxide method and doped with 3, 5 and 10 wt. % Bi2O3–PbO were sintered at 1,025 °C for 3 h. The X-ray diffraction patterns of the samples sintered, shown the presence of the
triclinic phase (β-BNO). In the measurements obtained at room temperature (25 °C) was observed that the largest values of
dielectric permittivity (ε′
r
) at frequency 100 kHz, were for the samples: BNO5Bi (5 wt. % Bi2O3) and BNO5Pb (5 wt. % PbO) with values ε′
r
~ 59.54 and ε′
r
~ 78.44, respectively. The smaller values of loss tangent (tan δ) were for the samples: BNO5Bi and BNO3Pb (3 wt. % PbO) with
values tan δ ~ 5.71 × 10−4 and tan δ ~ 2.19 × 10−4, respectively at frequency 33.69 MHz. The analysis as a function of temperature of the dielectric properties of the samples,
obtained at frequency 100 kHz, showed that the larger value of the relative dielectric permittivity was about ε′
r
~ 76.4 at temperature 200 °C for BNO5Pb sample, and the value smaller observed of dielectric loss was for BNO3Bi sample at
temperature 80 °C, with about tan δ ~ 5.4 × 10−3. The Temperature Coefficient of Capacitance (TCC) values at 1 MHz frequency, present a change of the signal from BNO (−55.06 ppm/°C)
to the sample doped of Bi: BNO3Bi (+86.74 ppm/°C) and to the sample doped of Pb: BNO3Pb (+208.87 ppm/°C). One can conclude
that starting from the BNO one can increase the doping level of Bi or Pb and find a concentration where one have TCC = 0 ppm/°C,
which is important for temperature stable materials applications like high frequency capacitors. The activation energy (H)
obtained in the process is approximately 0.55 eV for BNO sample and increase with the doping level. These samples will be
studied seeking the development ceramic capacitors for applications in radio frequency devices. 相似文献
7.
Shunhua Wu Shuang Wang Liying Chen Xiaoyong Wang 《Journal of Materials Science: Materials in Electronics》2008,19(6):505-508
The effects of Mn added during processing on the dielectric properties and microstructure of the BaTiO3-based ceramic materials system were discussed. Experiments show that a proper content of Mn can significantly increase dielectric
constant (ε) and reduce the dielectric loss (tanδ) in BaTiO3-based X7R ceramic materials. The results attribute to the reaction:
. When the system doped with 0.046mol% MnCO3 was sintered at 1240 °C for 4 h, the ε, tanδ and TCC were 5800, 1.6%, 0 ± 10% at 1 KHz respectively. 相似文献
8.
V VASUDEVAN R RAMESH BABU A REICHER NELCY G BHAGAVANNARAYANA K RAMAMURTHI 《Bulletin of Materials Science》2011,34(3):469-475
Semi-organic nonlinear optical material, L-lysine L-lysinium dichloride nitrate (2C6H15N2O2+_{2}^{+} · H + · NO3-_{3}^{-} · 2Cl − ) was synthesized at room temperature. Single crystals of L-LLDN were grown by slow cooling solution growth technique. The grown crystal was confirmed by powder X-ray diffraction analysis.
The crystalline perfection of the grown single crystal was characterized by high-resolution X-ray diffraction (HRXRD) studies.
The cut-off wavelength was determined by UV-vis transmission spectral analysis. The frequency doubling of the grown crystal
was confirmed by powder second harmonic generation (SHG) measurement. The refractive index and birefringence of the crystal
were determined using He–Ne laser source. Mechanical property of the crystal was determined by Vickers hardness tester. The
frequency and temperature dependence of dielectric constant (ε
r), dielectric loss (tan δ) and a.c. conductivity (σ
ac) were also measured. 相似文献
9.
Changyong Liu Dongyun Guo Chuanbin Wang Qiang Shen Lianmeng Zhang 《Journal of Materials Science: Materials in Electronics》2012,23(3):802-806
Bi4-xNdxTi3O12 (BNT-x, x = 0, 0.25, 0.50, 0.75 and 1.0) thin films were prepared on Pt/Ti/SiO2/Si substrates by a sol–gel method. The microstructure, ferroelectric and dielectric properties of BNT-x thin films were investigated.
The single-phase BNT-x thin films were obtained. With increasing Nd content, the preferred orientation changed from random
to (117) and surface morphologies changed from the mixture of rod- and plate-like grains to rod-like grains. The Nd substitution
improved the ferroelectric and dielectric properties of BTO films. BNT-x films showed better electrical properties at x = 0.50—1.0.
BNT-0.75 film exhibited the best electrical properties with remanent polarization (2P
r) of 26.6 μC/cm2, dielectric constant (ε
r) of 366 (at 1 MHz), dielectric loss (tanδ) of 0.034 (at 1 MHz), leakage current density (J) of ±3.0 × 10−6 A/cm2 (at ± 5 V) and fatigue-free characteristics. 相似文献
10.
Lunhong Ai Jing Jiang Liangchao Li 《Journal of Materials Science: Materials in Electronics》2010,21(2):211-212
Conducting polymeric nanocomposite containing Li–Ni–Sm–Fe–O spinel was synthesized by the chemical oxidizing of aniline in
the presence of LiNi0.5Sm0.08Fe1.92O4 particles. The dielectric and electric modulus properties of the as-prepared samples were investigated over a frequency range
from 106 to 109 Hz. The dielectric constant (ε′), dielectric loss (ε″) and dissipation factor (tan δ) for all samples presented relatively high values at low frequency and were found to decrease with the frequency. The values
of ε′, ε″ and tan δ of the nanocomposite were lower than that of the pristine PANI. Electric modulus analysis had been carried out to understand
the electrical relaxation process. The dielectric relaxation time for the nanocomposite became longer due to the introduction
of LiNi0.5Sm0.08Fe1.92O4 particles lowering the crystallinity of PANI. 相似文献
11.
The dielectric constant (K), loss (tanδ), and hence conductivity (σ) of SrTiO3 single crystals have been measured in the frequency region 102–107 Hz and in the temperature range 30°–350° C. Quenching, subjecting the crystals to high electric fields (a.c. or d.c.) and
X-ray orγ-ray irradiation, or a combination of these treatments, is found to bring about interesting changes in these properties. An
attempt is made to understand the results. 相似文献
12.
Dielectric properties of nanophase AgI are studied over the frequency range from 100 kHz to 3 MHz at different temperatures.
The values ofε, tanδ andσ
ac are considerably larger than those reported for crystalline pellets of AgI, but they show a similar trend in variation with
frequency and temperature. The increase in these values are attributed to the defect structure of the nano-particles. 相似文献
13.
Suhua Fan Fengqing Zhang Guitao Liu Qingbo Tian Luyi Zhu 《Journal of Materials Science: Materials in Electronics》2011,22(12):1778-1782
Bismuth-layered compound Ca0.15Sr1.85Bi4−xNdxTi5O18 (CSBNT, x = 0–0.25) ferroelectric ceramics samples were prepared by solid-state reaction method. The effects of Nd3+ doping on their ferroelectric and dielectric properties were investigated. The remnant polarization Pr of CSBNT ceramics
increases at beginning then decreases with increasing of Nd3+ doping level, and a maximum Pr value of 9.6 μC/cm2 at x = 0.05 was detected with a coercive field Ec = 80.2 kV/cm. Nd3+ dopant not only decreases the Curie temperature linearly, but also the dielectric constant (εr) and dielectric loss tangent (tan δ). The magnitudes of εr and tan δ at the frequency of 100 kHz are estimated to be 164 and 0.0083 at room temperature, respectively. 相似文献
14.
Polycrystalline samples of Ba5RTi3Nb7O30 [R=Nd, Eu, Gd], were prepared using high-temperature solid-state reaction technique. Preliminary X-ray structural analysis
of the compounds shows the formation of single phase compounds (orthorhombic crystal system) at room temperature. Detailed
studies of dielectric properties (ɛ, tanδ,σ) as a function of frequency (400 Hz to 10 kHz) and temperature (30° to 380°C) show that these compounds exhibit diffuse ferroelectric
phase transition. 相似文献
15.
Moti Ram 《Journal of Materials Science: Materials in Electronics》2012,23(4):936-939
The LiCo3/5Fe1/5Mn1/5VO4 compound was successfully synthesized by solution-based chemical method. The variation of dielectric constant (εr) with frequency at different temperatures shows a dispersive behavior at low frequencies. Temperature dependence of εr at different frequencies indicates dielectric anomalies in εr at temperature (Tmax) = 220, 235, 245, 260 and 275 °C with (εr)max ~ 6,830, 2,312, 1,224, 649 and 305 for 10, 50, 100, 200 and 500 kHz, respectively. The variation of tangent loss with frequency
at different temperatures shows the presence of dielectric relaxation in the material. The variation of relaxation time as
a function of temperature follows the Vogel-Fulcher relation. 相似文献
16.
A. Younis A. Hussain M. Asghar A. Manzoor S. Javed 《Journal of Superconductivity and Novel Magnetism》2011,24(4):1327-1332
The dielectric properties of Cu0.5Tl0.5Ba2Ca2−q
Mg
q
Cu3O10−δ
(q=0, 0.5, 1.0 1.5) superconductor samples were studied at two temperatures of 80 and 290 K by capacitance (C) and conductance (G) measurements with the test frequency (f) in the range of 10 KHz to 10 MHz. We have presented the measurements of the dielectric constants (ε′ and ε″), dielectric loss factor (tan δ) and ac-conductivity (σ
ac) as a function of frequency and temperature. A negative capacitance (NC) experience has been observed, which is most likely
due to different contact electrodes and superconductor samples’ Fermi levels. Since metals have their Fermi levels higher
than ceramics, there is a flow of the carriers from the ceramic samples towards the metal electrodes. The dielectric polarization
phenomenon is observed, which is due to dislodgment of mobile charges from their equilibrium position relative to fixed charges
of the reservoir layer. The improved inter plane coupling promoted by Mg substitution at Ca site would change the dielectric
response of Cu0.5Tl0.5Ba2Ca2−q
Mg
q
Cu3O10−δ
superconductors. To observe such effects in Mg doped Cu0.5Tl0.5Ba2Ca2−q
Mg
q
Cu3O10−δ
superconductors, di- electric measurements were carried out both at room temperature (290 K) and in the superconducting state
closer to the boiling point of liquid nitrogen (80 K). The excess conductivity arising due to superconducting state of material
has been determined, and its role in the mechanism of superconductivity is suggested. The negative dielectric constant (ε′) and dielectric loss factor (tan δ) show strong dispersion at low frequencies. The lower thermal agitation at 80 K may enhance the polarizability and hence
the dielectric constants (ε′ and ε″). 相似文献
17.
The dependences of relative dielectric permittivity, ε′
r, and tangent of dielectric loss angle, tg δ, of gallium phosphide (GaP) nanosolid on frequency and temperature were investigated. The GaP nanopowders are subglobular
in shape, with the average crystallite size of about 50 nm evaluated from Scherrer equation. It can be concluded that the
leakage current mechanism plays an important role in the dielectric loss of the GaP nanosolid. The dielectric characteristic
of the GaP nanosolid in the range 298–350 K allows to detect an ε′
r or tg δ peak at 303 K that is due to local phase transitions, probably in the high hydrostatic stress field of dislocations with
an edge component. Under the influence of an electric field, the high hydrostatic stress field of dislocations can undergo
changes in deformation, accompanied by drastic stress-induced changes in the order parameter near the phase transition temperature,
and hence, changes in the Gibbs free energy per unit volume can be found. 相似文献
18.
M. M. Nadoliisky M. P. Georgiev D. K. Nikolova V. A. Karadjova 《Journal of Materials Science: Materials in Electronics》2005,16(10):667-668
The article studies the dielectric properties, dc conductivity and ac conductivity of Be(IO3)2⋅4H2O single crystals. The dielectric constant ε has been defined for the three directions of the vectors a, b and c in the crystals in the temperature interval 280–340 K and frequency range 100 Hz–106 Hz. The crystals show strongly expressed anisotropy, at 20 ∘C and frequency 100 Hz εa = 235, εb = 30 and εc = 85. The frequency dependence of ε is evidence of the presence of low-frequency relaxation polarization in the crystals.
The activation energies of the three directions in the crystals have been derived from the temperature dependence of dc conductivity,
and they are 1.03 eV, 0.836 eV and 1.2 eV respectively. 相似文献
19.
Dielectric properties such as dielectric constant (ε′) and dielectric loss tangent (tan□δ) of mixed Mn-Zn-Er ferrites having
the compositional formula Mn0.58Zn0.37Fe2.05−xErx04 (where itx = 0.2, 0.4, 0.6, 0.8 and 1.0) were measured at room temperature in the frequency range 1–13 MHz using a HP 4192A
impedance analyser. Plots of dielectric constant (ε′) vs frequency show a normal dielectric behaviour of spinel ferrites.
The frequency dependence of dielectric loss tangent (tan δ) was found to be abnormal, giving a peak at certain frequency for
all mixed Mn-Zn-Er ferrites. A qualitative explanation is given for the composition and frequency dependence of the dielectric
constant and dielectric loss tangent. Plots of dielectric constant vs temperature have shown a transition near the Curie temperature
for all the samples of Mn-Zn-Er ferrites. However, Mn0.58Zn0.37Er1.0Fe1.05O4 does not show a transition. On the basis of these results an explanation for the dielectric mechanism in Mn-Zn-Er ferrites
is suggested. 相似文献
20.
Some anomalies observed in the dielectric properties of ceramics made from calcines of BaTiO3 are due to the presence of Ba2TiO4. These effects are only negligible if the Ba2TiO4 concentration in the calcine is less than 1 or 2 wt %. For concentrations greater than this, Ba2TiO4 inhibits the growth of BaTiO3 grains, shifts the Curie point towards low temperatures, decreasesε
r and causes large fluctuations in tanδ curves. 相似文献