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1.
Donglei Wei Yanlin Huang Jin Soo Kim Liang Shi Hyo Jin Seo 《Journal of Electronic Materials》2010,39(4):441-446
Well-crystallized Ca9ZnLi(PO4)7 ceramics were prepared by reactive pressureless sintering at atmospheric pressure. The single-phase Ca9ZnLi(PO4)7 ceramics were confirmed by x-ray diffraction (XRD). The dielectric and electrical properties were investigated over a wide
frequency range (1 Hz to 1 MHz) by complex impedance spectroscopy at different temperatures between 25°C and 600°C. A dielectric
anomaly was observed at 440°C, which might be related to the phase transition. The impedance Cole–Cole plot was used to analyze
the results of complex impedance measurements, revealing that the electrical properties depend strongly on frequency and temperature.
Two relaxation dispersions of the electrical parameters were found and analyzed in terms of bulk and grain-boundary ionic
transfer processes. The slope of the alternating-current (AC) conductivity over a wide range of temperatures provides activation
energies from 0.48 eV to 1.69 eV. These results suggest that the conduction process is of the mixed type. 相似文献
2.
Dielectric properties of a potassium sodium niobate (KNN) system in the microwave range up to GHz have rarely been studied. Since K0.5Na0.5NbO3 is the most common and typical type of KNN materials, non-doped K0.5Na0.5 NbO3 ceramics were synthesized at different temperatures (1080°C, 1090°C, 1100°C, and 1110°C) by a traditional solid reaction method for further characterization and analysis. The ceramics were in perovskite phase with orthorhombic symmetry. A small quantity of second phase was found in the 1110°C sintered specimen, which resulted from the volatilization of alkali oxides as the temperature increased. The complex permittivity was measured for the first time in the microwave range (8.2–12.4 GHz) and in the temperature range from 100°C to 220°C, and the effects of annealing on the dielectric properties were studied. The results indicate that the complex permittivity of KNN ceramics over the microwave range increases mainly due to high bulk density and the additional dielectric contributions of oxygen vacancies at high temperature. 相似文献
3.
Ping Wei Wen-Yu Zhao Chun-Lei Dong Bing Ma Qing-Jie Zhang 《Journal of Electronic Materials》2010,39(9):1803-1808
Filled skutterudite thermoelectric (TE) materials have been extensively studied to search for better TE materials in the past
decade. However, there is no detailed investigation about the thermal stability of filled skutterudite TE materials. The evolution
of microstructure and TE properties of nanostructured skutterudite materials fabricated with Ba0.3In0.2Co3.95Ni0.05Sb12/SiO2 core–shell composite particles with 3 nm thickness shell was investigated during periodic thermal cycling from room temperature
to 723 K in this work. Scanning electronic microscopy and electron probe microscopy analysis were used to investigate the
microstructure and chemical composition of the nanostructured skutterudite materials. TE properties of the nanostructured
skutterudite materials were measured after every 200 cycles of quenching in the temperature range from 300 K to 800 K. The
results show that the microstructure and composition of Ba0.3In0.2Co3.95Ni0.05Sb12/SiO2 nanostructured skutterudite materials were more stable than those of single-phase Ba0.3In0.2Co3.95Ni0.05Sb12 bulk materials. The evolution of TE properties indicates that the electrical and thermal conductivity decrease along with
an increase in the Seebeck coefficient with increasing quenching up to 2000 cycles. As a result, the dimensionless TE figure
of merit (ZT) of the nanostructured skutterudite materials remains almost constant. It can be concluded that these nanostructured skutterudite
materials have good thermal stability and are suitable for use in solar power generation systems. 相似文献
4.
M. Slankamenac T. Ivetić M. V. Nikolić N. Ivetić M. Živanov V. B. Pavlović 《Journal of Electronic Materials》2010,39(4):447-455
Impedance/admittance and dielectric spectroscopy were used to investigate the effect of temperature on the electrical response
of liquid-phase sintered Zn2SnO4-SnO2 ceramics. The measurements were performed over a wide frequency range (100 Hz to 10 MHz) at different temperatures. The real
and the imaginary part of the complex impedance traced semicircles in the complex plane. The resistance and the capacitance
of bulk and grain-boundary regions were determined by modeling the experimental results using several equivalent circuits
taking into account bulk deep trap states. Admittance complex diagrams were also determined in order to understand better
the conduction mechanisms occurring in the polycrystalline Zn2SnO4-SnO2 system. 相似文献
5.
A detailed analysis of the optical properties of filled tetrahedral semiconductors Li3AlN2 and Li3GaN2 has been performed, using the full potential linearized augmented plane wave method within the density functional theory.
The real and imaginary parts of the dielectric function ε(ω), the optical absorption coefficient I(ω), the reflectivity R(ω), and the electron energy loss function are calculated within the random phase approximation. The interband transitions responsible
for the structures in the spectra are specified. Looking at optical matrix element, we note that the major peaks are dominated
by transition from metal s, N 2p states to N 2p, Ga 3d states. The theoretical calculated optical properties and electron energy loss spectrum yield a static dielectric constant
of 5.34 and a plasmon energy of 19.47 eV for Li3GaN2. In the Li3AlN2 compound, the static dielectric constant decreases to 4.75 and yields a plasmon energy of 18.5 eV. The effect of spin–orbit
coupling on the optical properties is also investigated and found to be quite small, especially in the low-energy region.
In order to check the reliability of our calculations, analogous results obtained for Be3N2 in the same structure [space group Ia3(206)] are included in this work. 相似文献
6.
V. G. Zalessky V. V. Kaminski S. Hirai Y. Kubota N. V. Sharenkova 《Semiconductors》2018,52(4):411-413
The rare-earth semiconductor β-Ce2S3 compound samples were synthesized and their dielectric permittivity and electrical conductivity were measured in the temperature range 90–400 K. The energy-band structure has been determined. It is shown that the long-known large electrical parameter spread of semiconductor compounds close in composition to Ce2S3 is explained by the structure of impurity donor levels formed by cerium atoms and ions with different ionization degrees. 相似文献
7.
A comparative analysis of dielectric polarization processes in undoped and Bi-doped layers of modified As2Se3 has been performed. It is established that both the similarity and difference in polarization phenomena are due to specific
features of the internal structure of studied materials. The mechanism of the observed effects is discussed. 相似文献
8.
Polycrystalline Pr2CuTiO6 (PCT) ceramics exhibits dielectric, impedance and modulus characteristics as a possible material for microelectronic devices. PCT was synthesized through the standard solid-state reaction method. The dielectric permittivity, impedance and electric modulus of PCT have been studied in a wide frequency (100 Hz–1 MHz) and temperature (303–593 K) range. Structural analysis of the compound revealed a monoclinic phase at room temperature. Complex impedance Cole–Cole plots are used to interpret the relaxation mechanism, and grain boundary contributions towards conductivity have been estimated. From electrical modulus formalism polarization and conductivity relaxation behavior in PCT have been discussed. Normalization of the imaginary part of impedance (Z″) and the normalized imaginary part of modulus (M″) indicates contributions from both long-range and localized relaxation effects. The grain boundary resistance along with their relaxation frequencies are plotted in the form of an Arrhenius plot with activation energy 0.45 eV and 0.46 eV, respectively. The ac conductivity mechanism has been discussed. 相似文献
9.
R. Remya K. P. Murali S. N. Potty V. Priyadarshini R. Ratheesh 《Journal of Electronic Materials》2005,34(7):1076-1080
Hollandite-type Ba1−xSrxZnTi7O16 (x=0, 0.2, 0.4, 0.6, 0.8, and 1) ceramics have been synthesized by the conventional solid-state ceramic route. The phase
purity and microstructure of these compositions have been characterized using x-ray diffraction (XRD) and scanning electron
microscopy (SEM). The XRD analysis shows that an increase in strontium concentration in the A-site causes pairing of vacant
tunnel sites, and hence the structure becomes unstable due to the collapse of the tunnel walls. The dielectric properties
such as dielectric constant (εr), loss tangent (tan δ), and temperature variation of dielectric constant (τεr) have been measured up to the 13 MHz region. The present study shows that zinc hollandites have relatively high dielectric
constant and low loss tangent. The temperature variation of dielectric constant studies reveal that Ba-rich compositions have
high positive τεr and Sr-rich compositions have high negative τεr in the 0–100°C region. Proper tailor making of these compositions has been attempted to arrive at near-zero temperature variation
of the dielectric constant. 相似文献
10.
G. N. Isachenko A. Yu. Samunin V. K. Zaitsev E. A. Gurieva P. P. Konstantinov 《Semiconductors》2017,51(8):1005-1008
The thermoelectric properties of the Mg2Ge0.3Sn0.7 solid solution doped with Ga and Li are studied. The samples with a hole concentration as high as 5 × 1020 cm–3 are obtained. The temperature dependences of the thermopower, electrical conductivity, and thermal conductivity are measured in the range from room temperature to 800 K. A higher mobility of free charge carriers is observed in the samples doped with lithium than in the samples doped with gallium. The largest thermoelectric figure of merit in the samples under study amounts to 0.42 at 700 K. 相似文献
11.
BaTi5O11 film was prepared on Pt/Ti/SiO2/Si substrate by the laser chemical vapor deposition method. A single-phase BaTi5O11 film with ([`3] 22)/([`2] 23) (\overline{3} 22)/(\overline{2} 23) preferred orientation and columnar cross-section was obtained at high deposition rate (154.8 μm h−1). The dielectric constant (ε
r) of the BaTi5O11 film was 21, measured at 300 K and 1 MHz. The electrical properties of the BaTi5O11 film were investigated by ac impedance spectroscopy from 300 K to 1073 K at 102 Hz to 107 Hz. Plots of the real and imaginary parts of the impedance (Z′ and Z″) and electrical modulus (M′ and M″) in the above frequency and temperature range suggested the presence of two relaxation regimes, which were attributed to
grain and grain boundary responses. The ac conductivity plots as a function of frequency showed three types of conduction
process at elevated temperature. The frequency-independent plateau at low frequency was due to dc conductivity. The mid-frequency
conductivity was due to grain boundaries, while the high-frequency conductivity was due to grains. 相似文献
12.
Y. Yuan X. H. Zhou C. J. Zhao B. Li S. R. Zhang 《Journal of Electronic Materials》2010,39(11):2471-2475
High-temperature capacitors were prepared by the conventional oxide method based on Bi0.5Na0.5TiO3-BaTiO3-CaTiO3 (BNT-BT-CT) lead-free piezoelectric ceramics. BNT-BT is one of the promising candidates as a high-temperature relaxor, and
has a high Curie temperature and broadened dielectric constant. The addition of CT increases the dielectric constant at lower
temperatures and decreases the dielectric constant at higher temperatures, so that the variation of capacitance is decreased.
The effect of BT on the temperature characteristic of dielectric constant is contrary to that of CT. A single-phase rhombohedral
perovskite and square grains were obtained in this study. With the proper amount of BT and CT additions, the high-temperature
specification can be met: from −55°C to 200°C, the variation of capacitance is within ±15% of room-temperature capacitance. 相似文献
13.
A PbTiO3/Ba0.85Sr0.15TiO3/PbTiO3 (PT/BST15/PT) sandwich thin film has been prepared on Pt/Ti/SiO2/Si substrates by an improved sol-gel technique. It is found that such films under rapid thermal annealing at 700°C crystallize
more favorably with the addition of a PbTiO3 layer. They possess a pure, perovskite-phase structure with a random orientation. The polarization-electric field (P-E) hysteresis
loop and current-voltage (I-V) characteristic curves reveal that a PT/BST15/PT film exhibits good ferroelectricity at room
temperature. However, no sharp peak, only a weak maximum, is observed in the curves of the dielectric constant versus temperature.
The dielectric constant, loss tangent, leakage current density at 20 kV/cm, remnant polarization, and coercive field of the
PT/BST15/PT film are 438, 0.025, 1.3 × 10−6 Acm−2, 2.46 μCcm−2, and 41 kVcm−1, respectively, at 25°C and 10 kHz. The PT/BST15/PT film is a candidate material for high sensitivity elements for uncooled,
infrared, focal plane arrays (UFPAs) to be used at near ambient temperature. 相似文献
14.
Chunchun Li Huaicheng Xiang Changzhi Yin Ying Tang Yuncui Li Liang Fang 《Journal of Electronic Materials》2018,47(11):6383-6389
Li2Mg2TiO5, a rock-salt structured ceramic fabricated by a solid-state sintering technique, was characterized at the microwave frequency band. As a result, a microwave dielectric permittivity (εr) of 13.4, a quality factor of 95,000 GHz (at 11.3 GHz), and a temperature coefficient of resonance frequency (τf) of ? 32.5 ppm/°C have been obtained at 1320°C. Li2Mg2TiO5 ceramics have low permittivity, a broad processing temperature region, and a low loss, making them potential applications in millimeter-wave devices. Furthermore, B2O3 addition efficiently lowered the sintering temperature of Li2Mg2TiO5 to 900°C, which opens up their possible applications in low-temperature co-fired ceramics (LTCC) technology. 相似文献
15.
The results of studying dielectric relaxation processes in the Ge28.5Pb15S56.5 glassy system are presented. The existence of the non-Debye relaxation process caused by the distribution of relaxors over the relaxation time according to the Cole–Cole model is revealed. The energy and structural parameters are calculated: the activation energy Ep = 0.40 eV and the molecular dipole moment μ = 1.08 D. The detected features are explained within the model according to which the chalcogenide-glass structure is a set of dipoles formed by charged defects such as D+ and D–. 相似文献
16.
Sachin Tyagi Himanshu B. Baskey Ramesh Chandra Agarwala Vijaya Agarwala Trilok Chand Shami 《Journal of Electronic Materials》2011,40(9):2004-2014
SrFe12O19/ZnFe2O4 (SrFe11.2Zn0.8O19) nanoparticles having superparamagnetic nature were synthesized by coprecipitation of chloride salts using 7.5 M sodium hydroxide
solution. The resulting precursors were heat-treated at 900°C and 1200°C for 4 h in nitrogen atmosphere. During heat treatment
(HT), transformation proceeds through instantaneous nucleation and three-dimensional diffusion-controlled growth with an activation
energy of 175.9 kJ/mole. The hysteresis loops showed an increase in saturation magnetization from 1.044 emu/g to 61.227 emu/g
with increasing HT temperature. As-synthesized particles had sizes in the range of 20 nm to 25 nm with spherical shape. Further,
these spherically shaped nanoparticles tended to change their morphology to hexagonal plate and pyramidal shape with increasing
HT temperature. The effects of this systematic morphological transformation of nanoparticles on dielectric (complex permittivity
and permeability) and microwave absorption properties were estimated in the X-band (8.2 GHz to 12.2 GHz). The maximum reflection
loss of the composite powder reached −29.81 dB at 10.37 GHz, making it suitable for application in radar-absorbing materials. 相似文献
17.
Ba6−3xNd8+2xTi18O54 with x=0.25 (BNT-0.25, or simply, BNT) dielectric thin films with a thickness of 320 nm have been prepared on Pt-coated silicon
substrates by pulsed laser deposition (PLD) at the substrate temperature of 650°C in 20 Pa oxygen ambient. X-ray analysis
showed that the as-deposited films are amorphous and the films remain amorphous after a postannealing at 750°C for 30 min.
The dielectric constant of the BNT films has been determined to be about 80 with a low loss tan δ of about 0.006 at 1 MHz.
The capacitance-voltage (C-V), capacitance-frequency, and capacitance-temperature characteristics of a BNT capacitor with
Pt top electrode were measured. A low leakage-current density of 4×10−6 A/cm2 at 6 V was measured, and a preliminary discussion of the leakage-current mechanism is also given. It is proposed that amorphous
BNT-0.25 thin films will be a potential dielectric material for microwave applications. 相似文献
18.
The reflectance spectra of a p-Bi2Te3:Sn crystal are recorded in the range 50–7900 cm–1. The spectra possess features characteristic of charge-carrier plasma oscillations and a contribution of phonons. It is shown that the dielectric function that is used in the context of Drude–Lorentz theory and includes the contributions of hole plasma oscillations and two phonons adequately describes the experimental data obtained at room temperature and at a temperature of T = 78 K. 相似文献
19.
Ja Young Cho Young Soo Lim Soon-Mok Choi Kyoung Hun Kim Won-Seon Seo Hyung-Ho Park 《Journal of Electronic Materials》2011,40(5):1024-1028
We report the thermoelectric properties of spark plasma-sintered In4Se3-In4Te3 materials. For comparison, pure In4Se3 and In4Se3 (80 wt.%)/In4Te3 (20 wt.%) mixture samples were prepared. In4Se3 and In4Te3 powders were synthesized by a conventional melting process in evacuated quartz ampoules, and a spark plasma method was used
for the sintering of the pure In4Se3 and mixture samples. Thermoelectric and structural characterizations were carried out, and the mixing effect of In4Se3 and In4Te3 on the thermoelectric properties was investigated. 相似文献
20.
Huanfu Zhou Hong Wang Kecheng Li Haibo Yang Minghui Zhang Xi Yao 《Journal of Electronic Materials》2009,38(5):711-716
The influence of BaCu(B2O5) (BCB) addition on the sintering temperature and microwave dielectric properties of ZnO-2TiO2-Nb2O5 (ZTN) ceramic has been investigated using dilatometry, x-ray diffraction, scanning electron microscopy, and microwave dielectric
measurements. A small amount of BCB addition to ZTN can lower the sintering temperature from 1100°C to 900°C. The reduced
sintering temperature was attributed to the formation of the BCB liquid phase. The ZTN ceramics containing 3.0 wt.% BCB sintered
at 900°C for 2 h have good microwave dielectric properties of Q × f = 19,002 GHz (at 6.48 GHz), ε
r = 45.8 and τ
f
= 23.2 ppm/°C, which suggests that the ceramics can be applied in multilayer microwave devices, provided that Ag compatibility
exists. 相似文献