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1.
Thermoelectric materials are attractive since they can recover waste heat directly in the form of electricity. In this study,
the thermoelectric properties of ternary rare-earth sulfides LaGd1+x
S3 (x = 0.00 to 0.03) and SmGd1+x
S3 (x = 0.00 to 0.06) were investigated over the temperature range of 300 K to 953 K. These sulfides were prepared by CS2 sulfurization, and samples were consolidated by pressure-assisted sintering to obtain dense compacts. The sintered compacts
of LaGd1+x
S3 were n-type metal-like conductors with a thermal conductivity of less than 1.7 W K−1 m−1. Their thermoelectric figure of merit ZT was improved by tuning the chemical composition (self-doping). The optimized ZT value of 0.4 was obtained in LaGd1.02S3 at 953 K. The sintered compacts of SmGd1+x
S3 were n-type hopping conductors with a thermal conductivity of less than 0.8 W K−1 m−1. Their ZT value increased significantly with temperature. In SmGd1+x
S3, the ZT value of 0.3 was attained at 953 K. 相似文献
2.
Ternary rare-earth sulfides NdGd1+x
S3, where 0 ≤ x ≤ 0.08, were prepared by sulfurizing Ln2O3 (Ln = Nd, Gd) with CS2 gas, followed by reaction sintering. The sintered samples have full density and homogeneous compositions. The Seebeck coefficient,
electrical resistivity, and thermal conductivity were measured over the temperature range of 300 K to 950 K. All the sintered
samples exhibit a negative Seebeck coefficient. The magnitude of the Seebeck coefficient and the electrical resistivity decrease
systematically with increasing Gd content. The thermal conductivity of all the sintered samples is less than 1.9 W K−1 m−1. The highest figure of merit ZT of 0.51 was found in NdGd1.02S3 at 950 K. 相似文献
3.
Silver doped p-type Mg2Ge thin films were grown in situ at 773 K using magnetron co-sputtering from individual high-purity Mg and Ge targets. A sacrificial
base layer of silver of various thicknesses from 4 nm to 20 nm was initially deposited onto the substrate to supply Ag atoms,
which entered the growing Mg2Ge films by thermal diffusion. The addition of silver during film growth led to increased grain size and surface microroughness.
The carrier concentration increased from 1.9 × 1018 cm−3 for undoped films to 8.8 × 1018 cm−3 for the most heavily doped films, but it did not reach saturation. Measurements in the temperature range of T = 200–650 K showed a positive Seebeck coefficient for all the films, with maximum values at temperatures between 400 K and
500 K. The highest Seebeck coefficient of the undoped film was 400 μV K−1, while it was 280 μV K−1 for the most heavily doped film at ∼400 K. The electrical conductivity increased with silver doping by a factor of approximately
10. The temperature effects on power factors for the undoped and lightly doped films were very limited, while the effects
for the heavily doped films were substantial. The power factor of the heavily doped films reached a non-optimum value of ∼10−5 W cm−1 K−2 at 700 K. 相似文献
4.
A mechanical alloying (MA) process to transform elemental powders into solid Pb0.5Sn0.5Te with thermoelectric functionality comparable to melt-alloyed material is described. The room-temperature doping level and
mobility as well as temperature-dependent electrical conductivity, Seebeck coefficient, and thermal conductivity are reported.
Estimated values of lattice thermal conductivity (0.7 W m−1 K−1) are lower than some reports of functional melt-alloyed PbSnTe-based material, providing evidence that MA can engender the
combination of properties resulting in highly functional thermoelectric material. Though doping level and Sn composition have
not been optimized, this material exhibits a ZT value >0.5 at 550 K. 相似文献
5.
Jae-Hong Lim Mi Yeong Park Dong Chan Lim Bongyoung Yoo Jung-Ho Lee Nosang V. Myung Kyu Hwan Lee 《Journal of Electronic Materials》2011,40(5):1321-1325
Thermoelectric Sb
x
Te
y
films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containing different concentrations
of TeO2. Stoichiometric Sb
x
Te
y
films were obtained by applying a voltage of −0.15 V versus saturated calomel electrode (SCE) using a solution consisting
of 2.4 mM TeO2, 0.8 mM Sb2O3, 33 mM tartaric acid, and 1 M HNO3. The nearly stoichiometric Sb2Te3 films had a rhombohedral structure, R[`3]m R\bar{3}m , with a preferred orientation along the (015) direction. The films had hole concentration of 5.8 × 1018/cm3 and exhibited mobility of 54.8 cm2/Vs. A more negative potential resulted in higher Sb content in the deposited Sb
x
Te
y
films. Furthermore, it was observed that the hole concentration and mobility decreased with increasingly negative deposition
potential, and eventually showed insulating properties, possibly due to increased defect formation. The absolute value of
the Seebeck coefficient of the as-deposited Sb2Te3 thin film at room temperature was 118 μV/K. 相似文献
6.
In this paper, a novel and simple sodium alginate (SA) gel method was developed to prepare γ-Na
x
Co2O4. This method involved the chemical gelling of SA in the presence of Co2+ ions by cross-linking. After calcining at 700°C to 800°C, single-phase γ-Na
x
Co2O4 crystals were obtained. The arrangement of about 1 μm to 4 μm flaky particles exhibited a well-tiled structure along the plane direction of the flaky particles. SA not only acted as
the control agent for crystal growth, but also provided a Na source for the γ-Na
x
Co2O4 crystals. The electrical properties of γ-Na
x
Co2O4 ceramics prepared via ordinary sintering after cold isostatic pressing were investigated. The Seebeck coefficient and power
factor of the bulk material were 177 μV K−1 and 4.3 × 10−4 W m−1 K−2 at 850 K, respectively. 相似文献
7.
The temperature dependence of the thermal conductivity κ(T), electrical resistivity ρ(T), and Seebeck coefficient S(T) of Mg2Sn:Ag crystals with 0 at.% to 1 at.% Ag content were measured at T = 2 K to 400 K. The crystals were cut from ingots that were prepared by the vertical Bridgman method. Undoped samples show
a dramatic κ ∝ T
3 rise at low temperatures to a peak value κ
15K = 477 W m−1 K−1. This leads to exceptionally large phonon drag effects causing giant thermopower with S rising sharply to a peak value S
20K = 3000 μV K−1. At higher temperatures S decreases and changes sign to intrinsic values S ≈ −60 μV K−1. The addition of Ag changes the transport properties as follows: (a) κ decreases systematically, the peak shifts to 30 K and falls to 7 W m−1 K−1; (b) ρ changes from high to low values; (c) S(T) changes to a linear dependence with S
300K ≈ 150 μV K−1 to 200 μV K−1. 相似文献
8.
Yong Liu Yuan-Hua Lin Jinle Lan Bo-Ping Zhang Wei Xu Ce-Wen Nan Hongmin Zhu 《Journal of Electronic Materials》2011,40(5):1083-1086
Polycrystalline In2O3 ceramics co-doped with Zn and Nd were prepared by the spark plasma sintering (SPS) process, and microstructure and thermoelectric
(TE) transport properties of the ceramics were investigated. Our results indicate that co-doping with Zn2+ and Nd3+ shows a remarkable effect on the transport properties of In2O3-based ceramics. Large electrical conductivity (~130 S cm−1) and thermopower (~220 μV K−1) can be observed in these In2O3-based ceramic samples. The maximum power factor (PF) reaches 5.3 × 10−4 W m−1 K−2 at 973 K in the In1.92Nd0.04Zn0.04O3 sample, with a highest ZT of ~0.25. 相似文献
9.
Polycrystalline SnO2-based samples (Sn0.97−x
Sb0.03Zn
x
O2, x = 0, 0.01, 0.03) were prepared by solid-state reactions. The thermoelectric properties of SnO2 doped with Sb and Zn were investigated from 300 K to 1100 K. X-ray diffraction (XRD) analysis revealed all XRD peaks of all
the samples as identical to the rutile structure, except for the x = 0.03 sample, which had a small amount of Zn2SbO4 as a secondary phase. We found that the power factor of the x = 0.03 sample was significantly improved due to the simultaneous increase in the electrical conductivity and the Seebeck
coefficient. A power factor value of ∼2 × 10−4 W m−1 K−2 was obtained for the x = 0.03 sample at 1060 K, 126% higher than that for the undoped sample. 相似文献
10.
Tatsuya Sakamoto Tsutomu Iida Shota Kurosaki Kenji Yano Hirohisa Taguchi Keishi Nishio Yoshifumi Takanashi 《Journal of Electronic Materials》2011,40(5):629-634
The thermoelectric (TE) characteristics of Sb- and Al-doped n-type Mg2Si elemental devices fabricated using material produced from molten commercial doped polycrystalline Mg2Si were examined. The TE devices were prepared using a plasma-activated sintering (PAS) technique. To complete the devices,
Ni electrodes were fabricated on each end of them during the sintering process. To realize durable devices for large temperature
differences, thermodynamically stable Sb-doped Mg2Si (Sb-Mg2Si) was exposed to the higher temperature and Al-doped Mg2Si (Al-Mg2Si) was exposed to the cooler temperature. The devices consisted of segments of Sb-Mg2Si and Al-Mg2Si with sizes in the following ratios: Sb-Mg2Si:Al-Mg2Si = 4:1, 1:1, and 1:4. A device specimen composed solely of Sb-Mg2Si showed no notable deterioration even after aging for 1000 h, while some segmented specimens, such as those with Sb-Mg2Si:Al-Mg2Si = 1:1 and 1:4, suffered from a considerable drop in output current over the large ΔT range. The observed power generated by specimens with Sb-Mg2Si:Al-Mg2Si = 1:1 and 1:4 and sizes of 2 mm × 2 mm × 10 mm were 50.7 mW and 49.5 mW, respectively, with higher and lower temperatures
of 873 K and 373 K, respectively. For the sample composed solely of Sb-Mg2Si, a power of 55 mW was demonstrated. An aging test for up to 1000 h for the same ΔT range indicated drops in output power of between ∼3% and 20%. 相似文献
11.
Wei Liu Qiang Zhang Xinfeng Tang Han Li Jeff Sharp 《Journal of Electronic Materials》2011,40(5):1062-1066
Mg2(Si0.3Sn0.7)1−y
Sb
y
(0 ≤ y ≤ 0.04) solid solutions were prepared by a two-step solid-state reaction method combined with the spark plasma sintering
technique. Investigations indicate that the Sb doping amount has a significant impact on the thermoelectric properties of
Mg2(Si0.3Sn0.7)1−y
Sb
y
compounds. As the Sb fraction y increases, the electron concentration and electrical conductivity of Mg2(Si0.3Sn0.7)1−y
Sb
y
first increase and then decrease, and both reach their highest value at y = 0.025. The sample with y = 0.025, possessing the highest electrical conductivity and one of the higher Seebeck coefficient values among all the samples,
has the highest power factor, being 3.45 mW m−1 K−2 to 3.69 mW m−1 K−2 in the temperature range of 300 K to 660 K. Meanwhile, Sb doping can significantly reduce the lattice thermal conductivity
(κ
ph) of Mg2(Si0.3Sn0.7)1−y
Sb
y
due to increased point defect scattering, and κ
ph for Sb-doped samples is 10% to 20% lower than that of the nondoped sample for 300 K < T < 400 K. Mg2(Si0.3Sn0.7)0.975Sb0.025 possesses the highest power factor and one of the lower κ
ph values among all the samples, and reaches the highest ZT value: 1.0 at 640 K. 相似文献
12.
Current flow in an In-n-4H-SiC ohmic contact (n ≈ 3 × 1017 cm−3) has been studied by analyzing the temperature dependence of the per-unit-area contact resistance. It was found that the
thermionic emission across an ∼0.1-eV barrier is the main current flow mechanism and the effective Richardson constant is
∼2 × 10−2 A cm−2 K−1. 相似文献
13.
Y. Isoda S. Tada T. Nagai H. Fujiu Y. Shinohara 《Journal of Electronic Materials》2010,39(9):1531-1535
Mg2Si1−x
Sn
x
-system solid solutions are ecofriendly semiconductors that are promising materials for thermoelectric generators in the middle
temperature range. To produce a thermoelectric device, high-performance p- and n-type materials must be balanced. In this paper, p-type Mg2.00Si0.25Sn0.75 with Li and Ag double doping was prepared by the liquid–solid reaction method and hot-pressing. Effects of Li and Ag double
doping on thermoelectric properties were investigated in the temperature range from room temperature to 850 K. All sintered
compacts were identified as single-phase solid solutions with anti-fluorite structure. The carrier concentration increased
with the double doping. The temperature dependence of resistivity of the double-doped samples was similar to that of a metal.
The seebeck coefficient increased with temperature to a maximum value and then decreased in the intrinsic region. Thermal
conductivity decreased linearly with increasing temperature, reaching a minimum near the intrinsic region, and then increased
rapidly because of the contribution of the bipolar component. The dimensionless figure of merit reached 0.32 at 610 K for
Mg2.00Si0.25Sn0.75 double-doped with Li-5000 ppm and Ag-20000 ppm. 相似文献
14.
A. O. Evwaraye 《Journal of Electronic Materials》2010,39(6):751-755
n-Type 4H-SiC bulk samples with a net doping concentration of 2.5 × 1017 cm−3 were irradiated at room temperature with 1-MeV electrons. The high doping concentration plus a reverse bias of up to −13 V
ensures high electric field in the depletion region. The dependence of the emission rate on the electric field in the depletion
region was measured using deep-level transient spectroscopy (DLTS) and double-correlation deep-level transient spectroscopy
(DDLTS). The experimental data are adequately described by the phonon-assisted tunneling model proposed by Karpus and Pere. 相似文献
15.
Indium tin oxide (ITO) thin films doped with Au, Ni, or Pt (3.5 at.% to 10.5 at.%) were deposited on p-GaN epilayers (Mg ~4 × 1019 cm−3) using direct-current (DC) sputter codeposition. It was found that undoped ITO con- tacts to p-GaN exhibited leaky Schottky behavior, whereas the incorporation of a small amount of Au (3.5 at.% to 10.5 at.%) significantly
improved their ohmic characteristics. Compared with standard Ni/ITO contacts, the Au-doped ITO contacts had a similar specific
contact resistance in the low 10−2 Ω cm−2 range, but were more stable above 600°C and more transparent at blue wavelengths. These results provide support for the use
of Au-doped ITO ohmic contact to p-type GaN in high-brightness blue light-emitting diodes. 相似文献
16.
Evandro Daniel Calderaro Cotrim Luís Henrique de Carvalho Ferreira 《Analog Integrated Circuits and Signal Processing》2012,71(2):275-282
In this paper an ultra-low-power CMOS symmetrical operational transconductance amplifier (OTA) for low-frequency G
m
-C applications in weak inversion is presented. Its common mode input range and its linear input range can be made large using
DC shifting and bulk-driven differential pair configuration (without using complex approaches). The symmetrical OTA was successfully
verified in a standard CMOS 0.35-μm process. The measurements show an open loop gain of 61 dB and a unit gain frequency of
195 Hz with only 800 mV of power supply voltage and just 40 nW of power consumption. The transconductance is 66 nS, which
is suitable for low-frequency G
m
-C applications. 相似文献
17.
A. A. Lebedev V. V. Kozlovski S. V. Belov E. V. Bogdanova G. A. Oganesyan 《Semiconductors》2011,45(9):1145-1147
Carrier removal rate (V
d
) in p-6H-SiC in its irradiation with 8-MeV protons has been studied. The p-6H-SiC samples were produced by sublimation in vacuum. V
d
was determined by analysis of capacitance-voltage characteristics and from results of Hall effect measurements. It was found
that complete compensation of samples with initial value of N
a
− N
d
≈ 1.5 × 1018 cm−3 occurs at an irradiation dose of ∼1.1 × 1016 cm−2. In this case, the carrier removal rate was ∼130 cm−1. 相似文献
18.
The Seebeck coefficient, electrical resistivity, and thermal conductivity of Zr3Mn4Si6 and TiMnSi2 were studied. The crystal lattices of these compounds contain relatively large open spaces, and, therefore, they have fairly
low thermal conductivities (8.26 Wm−1 K−1 and 6.63 Wm−1 K−1, respectively) at room temperature. Their dimensionless figures of merit ZT were found to be 1.92 × 10−3 (at 1200 K) and 2.76 × 10−3 (at 900 K), respectively. The good electrical conductivities and low Seebeck coefficients might possibly be due to the fact
that the distance between silicon atoms in these compounds is shorter than that in pure semiconductive silicon. 相似文献
19.
Thermoelectric Properties of <Emphasis Type="Italic">n</Emphasis>-Type Multiple-Filled Skutterudites
Filled skutterudites are prospective intermediate temperature materials for␣thermoelectric power generation. CoSb3-based n-type filled skutterudites have good electrical transport properties with power factor values over 40 μW/cm K2 at elevated temperatures. Filling multiple fillers into the crystallographic voids of skutterudites would help scatter a
broad range of lattice phonons, thus resulting in lower lattice thermal conductivity values. We report the thermoelectric
properties of n-type multiple-filled skutterudites between 5 K and 800 K. The combination of different fillers inside the voids of the skutterudite
structure shows enhanced phonon scattering, and consequently a strong suppression of the lattice thermal conductivity. Very
good power factor values are achieved in multiple-filled skutterudite compared with single-element-filled materials. The dimensionless
thermoelectric figure of merit for n-type filled skutterudites is improved through multiple-filling in a wide temperature range. 相似文献
20.
The thermopower and electrical resistivity of alloys of GeTe and AgSbTe2 (TAGS) sintered at high pressure (up to 4.5 GPa) and high temperature (HPHT) have been studied from 300 K to 750 K. An apparatus
for measuring thermopower and electrical resistivity at temperatures >300 K is described. The linear temperature dependence
of thermopower and electrical conductivity indicates that these materials are likely to be degenerate semiconductors. At a
sintering pressure of 4.0 GPa, the calculated power factor shows a steady progression, reaching a maximum at a sintering temperature
of 800°C, with a subsequent decrease at the highest sintering temperature of 850°C. The maximum power factor of 4.32 × 10−3 W m−1 K−2 at ~675 K is ~25% higher than reported values. These results illustrate that HPHT processing is a feasible and controllable
way of tuning the properties of thermoelectric materials. 相似文献