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1.
Skutterudite compounds PbxBayCo4Sb11.5Te0.5 (x≤0.23,y≤0.27) with bcc crystal structure have been prepared by the high pressure and high temperature (HPHT) method. The study explored a chemical method for filling Pb and Ba atoms into the voids of CoSb3 to optimize the thermoelectric figure of merit ZT in the system of PbyBaxCo4Sb11.5Te0.5. The structure of PbxBayCo4Sb11.5Te0.5 skutterudites was evaluated by means of X-ray diffraction. The Seebeck coefficient, electrical resistivity and power factor were performed from room temperature to 710 K. Compared with Co4Sb11.5Te0.5, the thermal conductivity of Pb and Ba double-filled samples was reduced evidently. Among all filled samples, Pb0.03Ba0.27Co4Sb11.5Te0.5 showed the highest power factor of 31.64 μW cm−1 K−2 at 663 K. Pb0.05Ba0.25Co4Sb11.5Te0.5 showed the lowest thermal conductivity of 2.73 W m−1 K−1 at 663 K, and its maximum ZT value reached 0.63 at 673 K. 相似文献
2.
L. Wang K. F. Cai Y. Y. Wang H. Li H. F. Wang 《Applied Physics A: Materials Science & Processing》2009,97(4):841-845
Indium-filled skutterudites with nominal compositions of In
x
Co4Sb12 (x=0,0.1,0.2,0.3) were prepared by combining solvothermal synthesis and melting. The bulk samples were characterized by X-ray
diffraction and scanning electron microscopy, respectively. The Seebeck coefficient, electrical conductivity, and thermal
conductivity were measured from room temperature up to ∼773 K. Hall effect measurements were performed at room temperature.
The thermoelectric properties of the samples were significantly influenced by filling In into CoSb3. The dimensionless thermoelectric figure of merit, ZT, increased with increasing temperature and reached a maximum value of ∼0.79 for In0.1Co4Sb12 at 573 K. 相似文献
3.
4.
用熔融退火结合放电等离子烧结(SPS)技术制备了具有不同Ga填充含量的GaxCo4Sb12方钴矿化合物,研究了不同Ga含量对其热电传输特性的影响规律. Rietveld结构解析表明,Ga占据晶体学2a空洞位置,Ga填充上限约为0.22,当Ga的名义组成x≤0.25时,样品的电导率、室温载流子浓度Np随Ga含量的增加而增加,Seebeck系数随Ga含量的增加而减小. 室温下霍尔测试表明,每一个Ga授予框架0.9个电子,比Ga的氧化价态Ga3+小得多. 由于Ga离子半径相对较小,致使Ga填充方钴矿化合物的热导率κ及晶格热导率κL较其他元素填充的方钴矿化合物低. 当x=0.22时对应的样品在300K时的热导率和晶格热导率分别为3.05Wm-1·K-1和 2.86Wm-1·K-1.在600K下Ga0.22Co4.0Sb12.0样品晶格热导率达到最小,为1.83Wm-1·K-1,最大热电优值Z,在560K处达1.31×10-3K-1.
关键词:
skutterudite化合物
Ga原子填充
结构
热电性能 相似文献
5.
Partially filled polycrystalline p‐type skutterudites of nominal compositions Ybx Co3FeSb12 were synthesized and their thermoelectric properties characterized. The compositions and filling fractions were confirmed with a combination of Rietveld refinement and elemental analysis. The thermoelectric properties were evaluated from 300 K to 810 K. The Seebeck coefficient and resistivity increase while the thermal conductivity decreases with increasing Yb content. A maximum ZT value of 0.85 was obtained at 810 K. This work is part of a continuing effort to enhance the thermoelectric properties of p‐type skutterudites, as this class of materials continues to be of interest for thermoelectrics applications. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
I. Ruiz de Larramendi R. López-Antón J. I. Ruiz de Larramendi T. Rojo 《Applied Physics A: Materials Science & Processing》2008,93(3):655-661
Polycrystalline samples of Pr1−x
Sr
x
Fe0.8Co0.2 O3−δ
(x=0.1, 0.2, 0.3) (PSFC) were prepared by the combustion synthesis route at 1200°C. The structure of the polycrystalline powders
was analysed with X-ray powder diffraction data. The X-ray diffraction (XRD) patterns were indexed as the orthoferrite similar
to that of PrFeO3 having a single-phase orthorhombic perovskite structure (Pbnm). Pr1−x
Sr
x
Fe0.8Co0.2O3−δ
(x=0.1, 0.2, 0.3) films have been deposited on yttria-stabilized zirconia (YSZ) single-crystal substrates at 700°C by pulsed
laser deposition (PLD) for application to thin film solid oxide fuel cell cathodes. The structure of the films was analysed
by XRD, scanning electron microscopy (SEM) and atomic force microscopy (AFM). All films are polycrystalline with a marked
texture and present pyramidal grains in the surface with different size distributions. Electrochemical impedance spectroscopy
(EIS) measurements of PSFC/YSZ single crystal/PSFC test cells were conducted. The Pr0.7Sr0.3Fe0.8Co0.2O3−δ
film at 850°C presents a lower area specific resistance (ASR) value, 1.65 Ω cm2, followed by the Pr0.8Sr0.2Fe0.8Co0.2O3−δ
(2.29 Ω cm2 at 850°C) and the Pr0.9Sr0.1Fe0.8Co0.2O3−δ
films (5.45 Ω cm2 at 850°C). 相似文献
7.
A series of (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ (x=0.0–0.97, y=0.03) phosphors were synthesized by high-temperature solid-state reaction. The XRD patterns confirm the formation of a solid
solution of (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+. An intense tunable green light is observed with the increasing ratio of Sr/Ca. With an increase in x, the excitation and emission spectra show a redshift and blueshift, respectively, due to large centroid shift and small Stokes
shift. The temperature dependent luminescence is also investigated in the temperature range of 77–450 K. The Huang–Rhys factor
and the thermal-quenching temperature are determined. Intense green LEDs were successfully fabricated based on the (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ phosphor and near-ultraviolet (∼395 nm) GaN/blue (460 nm) InGaN chips. All the results indicate that the solid solution (Ca1−x−y
Sr
x
)Si2O2N2:yEu2+ is a promising phosphor applicable to near-UV and blue LEDs for solid-state lighting. 相似文献
8.
用熔融退火结合放电等离子烧结法制备了In0.3Co4Sb12-xSex(x=0—0.3)方钴矿热电材料,探讨了In的存在形式,系统研究了Se掺杂量对结构和热电性能的影响.结果表明:In可以填充到方钴矿二十面体空洞处,过量In在晶界处形成InSb第二相,Se对Sb的置换使晶格常数减小,In填充上限降低;In0.3Co4Sb12-xSex样品呈n型传导,随着Se掺杂量的增大,载流子浓度降低,电导率下降,Seebeck系数增大,功率因子有所降低;由于在结构中引入了质量波动及晶格畸变,适量的Se掺杂可以大幅降低材料晶格热导率;样品In0.3Co4Sb12和In0.3Co4Sb11.95Se0.05的最大ZT值均达到1.0以上.
关键词:
掺杂
填充式方钴矿
热电性能 相似文献
9.
Recently, we have demonstrated the successful synthesis of Fe
x
Co1−x
/Co
y
Fe3−y
O4 nanocomposites with various alkaline solutions by using surfactants-assisted-hydrothermal (SAH) process. In this article,
the synthesis of Fe
x
Co1−x
/CoyFe3−y
O4 nanocomposites with their sizes varying between 20 nm and 2 μm was reported. X-ray powder diffraction (XRD) analyses showed
that the surfactants, pH, precipitator, and temperature of the system play important roles in the nucleation and growth processes.
The magnetic properties tested by vibrating sample magnetometer (VSM) at room temperature exhibit ferromagnetic behavior of
the nanocomposites. These Fe
x
Co1−x
/Co
y
Fe3−y
O4 nanocomposites may have a potential application as magnetic carriers for drug targeting because of their excellent soft-magnetic
properties. 相似文献
10.
La2 − x
Sr
x
NiO4 +
δ
materials were investigated as cathodes for the electrochemical reduction of oxygen on a Ce1.9Gd0.1O1.95 (CGO10) electrolyte using cone-shaped electrodes together with electrochemical impedance spectroscopy. The area-specific
resistance (ASR) of the La2 − x
Sr
x
NiO4 +
δ
nickelates towards the reduction of oxygen is equal to the ASR of perovskites; however, it is not as low as for the best
Fe–Co-based perovskites. The lowest ASR is found for the compound La1.75Sr0.25NiO4 +
δ
with an ASR of 23.8 Ωcm2 measured on a cone-shaped electrode in air at 600 °C. It is suggested that difference in oxide ionic conductivity of the
nickelates is the main cause for the different activity of the nickelates towards the electrochemical reduction of oxygen. 相似文献
11.
LiAl
x
Mn2 − x
O4 and LiAl0.05Mn1.95O4 − y
F
y
spinel have been successfully synthesized by citric acid-assisted sol–gel method. The structure and physicochemical properties
of this as-prepared powder were investigated by electronic conductivity test, powder X-ray diffraction (XRD), scanning electron
microscopy (SEM), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge test in detail. The electronic
conductivity decreases with increasing of the content of doped Al. XRD patterns show that the diffraction of LiAl0.05Mn1.95O4 − y
F
y
samples is similar, with all the peaks indexable in the Fd3m space group, and a little impurity appears in the LiAl0.05Mn1.95O3.8F0.2 sample. SEM reveals that all LiAl0.05Mn1.95O4 − y
F
y
powders have the uniform, nearly cubic structure morphology with narrow size distribution which is less than 500 nm. Galvanostatic
charge–discharge test indicates that LiAl0.05Mn1.95O4 has the highest discharge capacity and electrochemical performance among all LiAl
x
Mn2 − x
O4 samples after 50 cycles, and the initial discharge capacity of LiAl0.05Mn1.95O4 − y
F
y
(y = 0, 0.02, 0.05, 0.1) is 123.9, 124.6, 124.9, and 125.0 mAh g−1, respectively, and their capacity retention ratios are 94.2%, 94.9%, 91.7%, and 89.9% after 50 cycles, respectively. EIS
indicates that LiAl0.05Mn1.95O3.98F0.02 have smaller charge transfer resistance than that of LiAl0.05Mn1.95O4 corresponding to the extraction of Li+ ions. 相似文献
12.
Several olivine phosphates were investigated in the last years as cathode materials for secondary lithium ion batteries. Among
these compounds, LiFe
x
Co1 − x
PO4 solid solutions might be interesting candidates because they should combine the high potential value of Co3+/Co2+ (higher than 4.5 V vs Li+/Li) with the relatively high charge–discharge rate of LiFePO4. Solid solutions were prepared by solid-state route and characterised by X-ray powder diffraction, cyclic voltammetry, impedance
spectroscopy and the Hebb–Wagner method. The results show that also low amount of iron induces high electronic conductivity
in the solid solutions. 相似文献
13.
Xiangqian Shen Mingquan Liu Fuzhan Song Yongwei Zhu 《Applied Physics A: Materials Science & Processing》2011,104(1):109-116
Sr1−x
La
x
Zn
x
Fe12−x
O19/poly(vinylpyrrolidone) (PVP) (0.0≤x≤0.5) precursor nanofibers were prepared by the sol–gel assisted electrospinning method from starting reagents of metal salts
and PVP. Subsequently, the Sr1−x
La
x
Zn
x
Fe12−x
O19 nanofibers with diameters of around 100 nm were obtained by calcination of the precursor at 800 to 1000°C for 2 h. The precursor
and resultant Sr1−x
La
x
Zn
x
Fe12−x
O19 nanofibers were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometer and
vibrating sample magnetometer. The grain sizes of Sr0.8La0.2Zn0.2Fe11.8O19 nanofibers are in a nanoscale from 40 to 48 nm corresponding to the calcination temperature from 800 to 1000°C. With La–Zn
substitution content increase from 0 to 0.5, the grain size and lattice constants for the Sr1−x
La
x
Zn
x
Fe12−x
O19 nanofibers obtained at 900°C show a steady reduction trend. With variations of the ferrite particle size arising from the
La–Zn substitution, the nanofiber morphology changes from the necklace-like structure linking by single elongated plate-like
particles to the structure building of multi-particles on the nanofiber cross-section. The specific saturation magnetization
of Sr1−x
La
x
Zn
x
Fe12−x
O19 nanofibers initially increases with the La–Zn content, reaching a maximum value 72 A m2 kg−1 at x=0.2, and then decreases with a further La–Zn content increase up to x=0.5, while the coercivity exhibits a continuous reduction from 413 (x=0) to 219 kA m−1 (x=0.5). The mechanism for the La–Zn substitution and the nanofiber magnetic property are analyzed. 相似文献
14.
K. Ben Kamel N. Amdouni A. Abdel-Ghany K. Zaghib A. Mauger F. Gendron C.M. Julien 《Ionics》2008,14(2):89-97
A series of LiNi
x
Mn
y
Co
z
O2 (x = y, z = 1 − 2y) oxides have been synthesized by “chimie douce” and investigated as positive electrodes in rechargeable lithium batteries.
Layered LiNi
y
Mn
y
Co1 − 2y
O2 materials with high homogeneity and crystallinity were synthesized using the wet-chemical method assisted by carboxylic acid
as the polymeric agent. The long range and local structural properties are investigated with experiments including X-ray diffraction,
Fourier transform infrared spectroscopy, and electron paramagnetic resonance spectroscopy. The evolution of the structure
is discussed as a function of the cobalt content that confers layer-like behavior on the framework. Electrochemical performance
of LiNi
y
Mn
y
Co1 − 2y
O2 oxides is tested in cells using nonaqueous 1 M LiPF6 dissolved in ethylene carbonate–diethyl carbonate. Charge–discharge profiles are investigated as a function of the rate capability
and the voltage window. A relation is found between the gravimetric capacity and the cation disorder of the positive electrode
as indicated by structural analysis. Fast lithium extraction attributed to the larger interslab space has been observed in
the cobalt-rich oxides.
Paper presented at the 11th Euro-Conference on Science and Technology of Ionics, Batz-sur-Mer, France, 9–15 Sept. 2007. 相似文献
15.
F. Yan T.J. Zhu X.B. Zhao S.R. Dong 《Applied Physics A: Materials Science & Processing》2007,88(2):425-428
Microstructures and thermoelectric properties of Ge1Sb2Te4 and Ge2Sb2Te5 chalcogenide semiconductors have been investigated to explore the possibility of their thermoelectric applications. The phase
transformation from the face-centered cubic to hexagonal structure was observed in Ge2Sb2Te5 compounds prepared by the melt spinning technique. The Seebeck coefficient and electrical resistivity of the alloys were
increased due to the enhanced scattering of charge carriers at grain boundaries. The maximum power factors of the rapidly
solidified Ge1Sb2Te4 and Ge2Sb2Te5 attained 0.975×10-3 W m-1K-2 at 750 K and 0.767×10-3 W m-1K-2 at 643 K respectively, higher than those of water quenched counterparts, implying that thermoelectric properties of GeSbTe
based layered compounds can be improved by grain refinement. The present results show this class of chalcogenide semiconductors
is promising for thermoelectric applications.
PACS 84.60.Rb; 81.05.Hd; 72.20.Pa; 64.70.Kb; 61.66.Fn 相似文献
16.
L. N. Luk’yanova V. A. Kutasov P. P. Konstantinov V. V. Popov 《Physics of the Solid State》2010,52(8):1599-1605
The specific features of the variation in the thermoelectric figure-of merit Z for p-type bismuth- and antimony-chalcogenide-based solid solutions p-(Bi,Sb)2(Te,Se)3 have been analyzed with allowance made for the data amassed in the investigation of thermoelectric and galvanomagnetic properties.
It has been shown that, in the samples with optimum carrier concentrations, the increase in Z in the multicomponent p-Bi2 − x
Sb
x
Te3 − y
Se
y
composition (x = 1.3, y = 0.06) in the temperature range 300–370 K is mediated by the high carrier mobility and the low lattice thermal conductivity.
The higher effective mass of the density of states and the larger slope of the temperature dependence of the mobility as compared
to the other compositions bring about an increase in Z in the p-Bi2 − x
Sb
x
Te3 solid solution for x = 1.6 in the temperature range 370–550 K. The increase in the figure-of merit reached in the compositions under study stems
also from the increasing contraction of constant-energy ellipsoids along the binary and bisector directions and from the change
in the angle θ between the principal axes of the ellipsoids and the crystallographic axes. 相似文献
17.
The preparation of (La9.33−2x/3Sr
x
□0.67−x/3)Si6O24O2 (0 ≤ x ≤ 2) samples with different amounts of cation vacancies is reported. Structure and unit-cell parameters were deduced by Rietveld
analysis of XRD patterns. Structural features that enhance oxygen conductivity in Sr-doped apatites are discussed. Up to three
components were detected in 29Si MAS-NMR spectra which change with the amount and distribution of cation vacancies. In general, oxygen conductivity increases
with the amount of vacancies at La1 (6h) sites, passing through a maximum for x = 0.4. In the case of activation energy, a minimum is detected near x = 1.2, indicating that entropic and enthalpic change in different ways. The presence of cation vacancies should enhance oxygen
hopping along c-axis; however, the analysis of the frequency dependence of conductivity suggests that oxygen motions are produced along three
axes. 相似文献
18.
A. A. Kozlovskii V. F. Khirnyi A. V. Semenov V. M. Puzikov 《Physics of the Solid State》2011,53(4):707-716
The electrical conductivity and Seebeck effect in ceramics based on cobaltites Ho1 − x
Sr
x
CoO3 − δ (x = 0.65, 0.75, 0.85, 0.95) and Er1 − x
Sr
x
CoO3 − δ (x = 0.75, 0.85, 0.95) with a perovskite-like structure have been investigated in the temperature range T > 77 K. All the compounds under study are characterized by the variable-range-hopping conductivity with the temperature dependence
of the electrical resistivity corresponding to the Mott law. It has been found that, in the Ho0.35Sr0.65CoO3 − δ compound, thermally excited Co3+ ions contribute to the electrical conductivity with an increase in temperature to 250 K. The Seebeck coefficient of the systems
studied decreases as the strontium concentration and temperature increase. It has been shown that, for an adequate explanation
of this behavior, proper allowance must be made for the splitting of the 3d levels, as well as for the charge disproportionation of the cobalt ions. 相似文献
19.
Oxygen ion conduction in La0.9Sr0.1Ga1−xMxO3−δ (M=Cr, Fe; x=0 – 0.20), LaGa1−xMxO3−δ (M=Co, Ni; x=0.20 – 0.60), LaGa1−x−yCoxMgyO3−δ (x=0.35 – 0.60; y=0.10 – 0.25) and LaGa0.85−xMg0.15(Nb0.33Mg0.66)xO3−δ (x=0 – 0.20) is reported. At temperatures below 1200 K the ionic conductivity of La(Ga,M)O3−δ (M=Co, Ni) increases with increasing oxygen nonstoichiometry, but is lower than for La(Ga,Mg)O3−δ and (La,Sr)GaO3−δ. Co-doping with Nb and Mg was found to result in decreasing ionic transport in La(Ga,Nb,Mg)O3−δ due to blocking of oxygen sites by Nb5+. Small additions of Fe to the B-site of La0.9Sr0.1GaO3−δ increase the ionic conductivity, whereas substitution of Cr for Ga has the opposite effect. Incorporation of transition metal
cations into the Ga site leads to a higher p-type electronic conductivity in all studied perovskites.
Paper presented at the 6th Euroconference on Solid Sate Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. 相似文献
20.
Here we report the synthesis, chemical stability, and electrical conductivity of Ti-doped perovskite-type BaCe0.8-x
Ti
x
Y0.2O3-δ
(x = 0.05, 0.1, 0.2, and 0.3; BCTY). Samples were synthesized by conventional solid state (ceramic) reaction from corresponding
metal salts and oxides at elevated temperature of 1,300–1,500 °C in air. The powder X-ray diffraction confirmed the formation
of a simple cubic perovskite-type structure with a lattice constant of a = 4.374(1), 4.377(1), and 4.332(1) ? for x = 0.05, 0.1, and 0.2 members of BCTY, respectively. Like BaCe0.8Y0.2O3-δ
(BCY), Ti substituted BCTY was found to be chemically not stable in 100% CO2 and form BaCO3 at elevated temperature. The bulk electrical conductivity of BCTY decreased with increasing Ti content and the x = 0.05 member exhibited the highest conductivity of 2.3 × 10−3 S cm−1 at 650 °C in air, while a slight increase in the conductivity, especially at low temperatures (below 600 °C), was observed
in humidified atmospheres. 相似文献