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1.
T. J. Zhu C. Yu J. He S. N. Zhang X. B. Zhao Terry M. Tritt 《Journal of Electronic Materials》2009,38(7):1068-1071
The thermoelectric properties of the Zintl compound YbZn2Sb2 with isoelectronic substitution of Zn by Mn in the anionic (Zn2Sb2)2− framework have been studied. The p-type YbZn2−x
Mn
x
Sb2 (0.0 ≤ x ≤ 0.4) samples were prepared via melting followed by annealing and hot-pressing. Thermoelectric property measurement showed
that the Mn substitution effectively lowered the thermal conductivity for all the samples, while it significantly increased
the Seebeck coefficient for x < 0.2. As a result, a dimensionless figure of merit ZT of approximately 0.61 to 0.65 was attained at 726 K for x = 0.05 to 0.15, compared with the ZT of ~0.48 in the unsubstituted YbZn2Sb2. 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.
Alex Zevalkink Jessica Swallow G. Jeffrey Snyder 《Journal of Electronic Materials》2012,41(5):813-818
Ca5Al2Sb6 is a relatively inexpensive Zintl compound exhibiting promising thermoelectric efficiency at temperatures suitable for waste
heat recovery. Motivated by our previous studies of Ca5Al2Sb6 doped with Na and Zn, this study focuses on doping with Mn2+ at the Al3+ site. While Mn is a successful p-type dopant in Ca5Al2Sb6, we find that incomplete dopant activation yields lower hole concentrations than obtained with either previously investigated
dopant. High-temperature Hall effect and Seebeck coefficient measurements show a transition from nondegenerate to degenerate
semiconducting behavior in Ca5Al2−x
Mn
x
Sb6 samples (x = 0.05, 0.1, 0.2, 0.3, 0.4) with increasing Mn content. Ultimately, no improvement in zT is achieved via Mn doping, due in part to the limited carrier concentration range achieved. 相似文献
4.
Norihiko L. Okamoto Tatsuya Koyama Kyosuke Kishida Katsushi Tanaka Haruyuki Inui 《Journal of Electronic Materials》2010,39(9):1640-1644
We have investigated phase relationships of the sesquisilicide alloys in the Ru-Mn-Si system. A series of chimney–ladder phases
Ru1−x
Mn
x
Si
y
(0.14 ≤ x ≤ 0.97, 1.584 ≤ y ≤ 1.741) are formed over a wide compositional range between Ru2Si3 and Mn4Si7. We also investigated thermoelectric properties of the directionally solidified Ru1−x
Mn
x
Si
y
alloys as a function of Mn content and temperature. The dimensionless figure of merit ZT for alloys with high Mn content (x ≥ 0.75) increases as the Mn content increases. The alloy with x = 0.90 exhibits ZT as high as 0.76 at 874 K. 相似文献
5.
In order to develop practical thermoelectric materials consisting solely of environmentally friendly elements, we investigated
the thermoelectric properties of the Al10Mn3-type (P63/mmc, hp26) Al77−x
Mn23Si
x
alloys and the Al102Mn24Si12-type (Pm-3, cP138) Al82−x
Mn5.5Fe12.5Si
x
alloys, both of which possess a pseudogap at the Fermi level. The formation range in which the single phase is obtained was
determined for these two phases. The electrical resistivity, Seebeck coefficient, and thermal conductivity of the samples
involving no secondary phase were measured over the temperature range of 2 K to 300 K. It is found that the thermoelectric
properties of these phases are qualitatively accounted for in terms of the pseudogap at the Fermi level in the electronic
density of states and the disordering in local atomic arrangements. 相似文献
6.
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
7.
Ramesh Chandra Mallik Christian Stiewe Gabriele Karpinski Ralf Hassdorf Eckhard Müller 《Journal of Electronic Materials》2009,38(7):1337-1343
The properties of Co4Sb12 with various In additions were studied. X-ray diffraction revealed the presence of the pure δ-phase of In0.16Co4Sb12, whereas impurity phases (γ-CoSb2 and InSb) appeared for x = 0.25, 0.40, 0.80, and 1.20. The homogeneity and morphology of the samples were observed by Seebeck microprobe and scanning
electron microscopy, respectively. All the quenched ingots from which the studied samples were cut were inhomogeneous in the
axial direction. The temperature dependence of the Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity (κ) was measured from room temperature up to 673 K. The Seebeck coefficient of all In-added Co4Sb12 materials was negative. When the filler concentration increases, the Seebeck coefficient decreases. The samples with In additions
above the filling limit (x = 0.22) show an even lower Seebeck coefficient due to the formation of secondary phases: InSb and CoSb2. The temperature variation of the electrical conductivity is semiconductor-like. The thermal conductivity of all the samples
decreases with temperature. The central region of the In0.4Co4Sb12 ingot shows the lowest thermal conductivity, probably due to the combined effect of (a) rattling due to maximum filling and
(b) the presence of a small amount of fine-dispersed secondary phases at the grain boundaries. Thus, regardless of the non-single-phase
morphology, a promising ZT (S
2
σT/κ) value of 0.96 at 673 K has been obtained with an In addition above the filling limit. 相似文献
8.
Michihiro Ohta Atsushi Yamamoto Haruhiko Obara 《Journal of Electronic Materials》2010,39(9):2117-2121
Chevrel-phase sulfides M
x
Mo6S8 (M, Cr, Mn, Fe, Ni; x: 1.3, 2.0) were prepared by reacting appropriate amounts of M, Mo, and MoS2 powders. The samples were then consolidated by pressure-assisted sintering to fabricate dense compacts. While Cr1.3Mo6S8 crystallized in a triclinic structure, Mn1.3Mo6S8, Fe1.3Mo6S8, and Ni2.0Mo6S8 crystallized in a hexagonal structure. The Seebeck coefficient, electrical resistivity, and thermal conductivity of the sintered
samples were measured over the temperature range of 300 K to 973 K. All the samples exhibited a positive Seebeck coefficient.
The Seebeck coefficient, electrical resistivity, and thermal conductivity of M1.3Mo6S8 (M: Cr, Mn, Fe) were almost identical and increased with temperature. However, the corresponding values and temperature dependent
behavior of Ni2.0Mo6S8 were different from those of M1.3Mo6S8 (M: Cr, Mn, Fe). For Ni2.0Mo6S8, as temperature increased, the Seebeck coefficient and thermal conductivity increased while the electrical resistivity decreased.
The highest value of the thermoelectric figure of merit (0.17) was observed in Cr1.3Mo6S8 at 973 K. 相似文献
9.
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
10.
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
11.
Ca
z
Co4−x
(Fe/Mn)
x
Sb12 skutterudites were prepared by mechanical alloying and hot pressing. The phases of mechanically alloyed powders were identified
as γ-CoSb2 and Sb, but they were transformed to δ-CoSb3 by annealing at 873 K for 100 h. All specimens had a positive Hall coefficient and Seebeck coefficient, indicating p-type conduction by holes as majority carriers. For the binary CoSb3, the electrical conductivity behaved like a nondegenerate semiconductor, but Ca-filled and Fe/Mn-doped CoSb3 showed a temperature dependence of a degenerate semiconductor. While the Seebeck coefficient of intrinsic CoSb3 increased with temperature and reached a maximum at 623 K, the Seebeck coefficient increased with increasing temperature
for the Ca-filled and Fe/Mn-doped specimens. Relatively low thermal conductivity was obtained because fine particles prepared
by mechanical alloying lead to phonon scattering. The thermal conductivity was reduced by Ca filling and Fe/Mn doping. The
electronic thermal conductivity was increased by Fe/Mn doping, but the lattice thermal conductivity was decreased by Ca filling.
Reasonable thermoelectric figure-of-merit values were obtained for Ca-filled Co-rich p-type skutterudites. 相似文献
12.
Y. Chen T. J. Zhu S. H. Yang S. N. Zhang W. Miao X. B. Zhao 《Journal of Electronic Materials》2010,39(9):1719-1723
A new preparation process combining melt spinning and hot pressing has been developed for the (Ag
x
SbTe
x/2+1.5)15(GeTe)85 (TAGS-85) system. Compared with samples prepared by the traditional air-quenching and hot-pressing method, electrical conductivity
and thermal conductivity are lowered. The thermoelectric performance of the TAGS-85 samples varied with changing Ag content
and reached the highest ZT of 1.48 when x was 0.8 for the melt-spun sample, compared with the maximum ZT of 1.36 for the air-quenched sample. The Seebeck coefficient of the melt-spun TAGS-85 alloys was improved, while both the
electrical conductivity and thermal conductivity were decreased. The net result of this process is to effectively enlarge
the temperature span of ZT > 1, which will benefit industrial application. 相似文献
13.
The thermoelectric properties of cobalt-doped compounds Co
x
Ti1−x
S2 (0 ≤ x ≤ 0.3) prepared by solid-state reaction were investigated from 5 K to 310 K. It was found that the electric resistivity ρ and absolute thermopower |S| for all the doped compounds decreased significantly with increasing Co content over the whole temperature range investigated.
The increased lattice thermal conductivity of the doped compounds would imply enhancement of the acoustic velocity. Moreover,
the ZT value of the doped compounds was improved over the whole temperature range investigated, and specifically reached 0.03 at
310 K for Co0.3Ti0.7S2, being about 66% larger than that of TiS2. 相似文献
14.
Yanjie Cui James R. Salvador Jihui Yang Hsin Wang Gisele Amow Holger Kleinke 《Journal of Electronic Materials》2009,38(7):1002-1007
Three Ta-doped strontium titanates were prepared as potential candidates for n-type thermoelectric oxides. The purity of the polycrystalline samples of SrTi1−x
Ta
x
O3 (x = 0.05 to 0.14) were characterized by means of powder x-ray diffraction and electron probe micro analysis (EPMA). We present
the results of Seebeck coefficient, electrical conductivity, and thermal conductivity measurements performed at high temperatures. 相似文献
15.
J.Q. Li S.P. Li Q.B. Wang L. Wang F.S. Liu W.Q. Ao 《Journal of Electronic Materials》2011,40(10):2063-2068
Ce-doped Pb1−x
Ce
x
Te alloys with x = 0, 0.005, 0.01, 0.015, 0.03, and 0.05 were prepared by induction melting, ball milling, and spark plasma sintering techniques.
The structure and thermoelectric properties of the samples were investigated. X-ray diffraction (XRD) analysis indicated that
the samples were of single phase with NaCl-type structure for x less than 0.03. The lattice parameter a increases with increasing Ce content. The lower Ce-doped samples (x = 0.005 and 0.01) showed p-type conduction, whereas the pure PbTe and the higher doped samples (x = 0, 0.015, 0.03, and 0.05) showed n-type conduction. The lower Ce-doped samples exhibited a much higher absolute Seebeck coefficient, but the higher electrical
resistivity and higher thermal conductivity compared with pure PbTe resulted in a lower figure of merit ZT. In contrast, the higher Ce-doped samples exhibited a lower electrical resistivity, together with a lower absolute Seebeck
coefficient and comparable thermal conductivity, leading to ZT comparable to that of PbTe. The lowest thermal conductivity (range from 0.99 W m−1 K−1 at 300 K to 0.696 W m−1 K−1 at 473 K) was found in the alloy Pb0.95Ce0.05Te due to the presence of the secondary phases, leading to a ZT higher than that of pure PbTe above 500 K. The maximum figure of merit ZT, in the alloy Pb0.95Ce0.05Te, was 0.88 at 673 K. 相似文献
16.
Indium-filled skutterudites are promising power generation thermoelectric materials due to the presence of an InSb nanostructure
that lowers the thermal conductivity. In this work, we have investigated thermoelectric properties of triple-filled Ba
x
Yb
y
In
z
Co4Sb12 (0 ≤ x, y, z ≤ 0.14 actual) compounds by measuring their Seebeck coefficient, electrical conductivity, thermal conductivity, and Hall
coefficient. All samples were prepared by a melting–annealing–spark plasma sintering method, and their structure was characterized
by x-ray diffraction and transmission electron microscopy (TEM). TEM results show the development of an InSb nanostructure
with a grain size of 30 nm to 500 nm. The nanostructure is present in all samples containing In and is also detected by specific
heat measurements. The Seebeck and Hall coefficients indicate that the compounds are n-type semiconductors. Electrical conductivity increases with increasing Ba content. Thermal conductivity is strongly suppressed
upon the presence of In in the skutterudite structure, likely due to enhanced boundary scattering of phonons on the nanometer-scale
InSb inclusions. The highest thermoelectric figure of merit is achieved with Ba0.09Yb0.07In0.06Co4Sb11.97, reaching ZT = 1.25 at 800 K. 相似文献
17.
Polycrystalline p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric (TE) alloys containing a small amount (vol.% ≤5) of SiC nanoparticles were fabricated by mechanical alloying
and spark plasma sintering. It was revealed that the effects of SiC addition on TE properties can be different between p-type and n-type Bi2Te3-based alloys. SiC addition slightly increased the power factor of the p-type materials by decreasing both the electrical resistivity (ρ) and Seebeck coefficient (α), but decreased the power factor of n-type materials by increasing both ρ and α. Regardless of the conductivity type, the thermal conductivity was reduced by dispersing SiC nanoparticles in the Bi2Te3-based alloy matrix. As a result, a small amount (0.1 vol.%) of SiC addition increased the maximum dimensionless figure of
merit (ZT
max) of the p-type Bi0.5Sb1.5Te3 alloys from 0.88 for the SiC-free sample to 0.97 at 323 K, though no improvement in TE performance was obtained in the case
of n-type Bi2Te2.7Se0.3 alloys. Importantly, the SiC-dispersed alloys showed better mechanical properties, which can improve material machinability
and device reliability. 相似文献
18.
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
19.
Girish C. Tewari T.S. Tripathi P. Kumar A.K. Rastogi S.K. Pasha Govind Gupta 《Journal of Electronic Materials》2011,40(12):2368-2373
The thermoelectric figure of merit (ZT) of the layered antiferromagnetic compound CuCrS2 is further improved with increase in the Cr-vacancy disorder on sintering above 900°C. X-ray photoelectron spectroscopy and
x-ray diffraction refinement results for different samples show that the chromium atoms are transferred from the filled layers
to the vacant sites between the layers. This atomic disorder increases the electrical conductivity (σ) due to self-doping of the charge carriers and reduces thermal conductivity (κ) due to increase in phonon scattering. The Seebeck coefficient (S) is p-type and remains nearly temperature independent with values between 150 μV/K and 450 μV/K due to electronic doping in different samples. 相似文献
20.
H. L. Gao X. X. Liu T. J. Zhu S. H. Yang X. B. Zhao 《Journal of Electronic Materials》2011,40(5):830-834
This study focuses on Sb-doped Mg2(Si,Sn) thermoelectric material. Samples were successfully fabricated using a hybrid synthesis method consisting of three
different processes: induction melting, solid-state reaction, and a hot-press sintering technique. We found that the carrier
concentration increased with Sb content, while the Seebeck coefficient exhibited a decreasing trend. Sb doping was shown to
improve the power factor and thermoelectric figure of merit compared with the undoped material, yielding a peak figure of
merit (ZT) of ~0.55 at 620 K, while leaving the band gap of Mg2Si0.7Sn0.3 almost unchanged. 相似文献