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1.
Effect of Chromium Doping on the Thermoelectric Properties
of Bi2Te3: Cr
x
Bi2Te3 and Cr
x
Bi2−x
Te3
The thermoelectric (TE) properties of Bi2Te3 compounds intercalated and substituted with Cr, namely Cr x Bi2Te3 and Cr x Bi2?x Te3, respectively, have been investigated to study the influence of chromium on the TE properties of Bi2Te3. The Seebeck coefficients were found to be positive for all the samples in the temperature range between 300 K and 550 K. Although no effective enhancement of the Seebeck coefficient was observed, doping with Cr by means of either substitution or intercalation clearly not only improved the electrical conductivity but also lowered the thermal conductivity of Bi2Te3. As a result of the improvement, the figure of merit ZT is increased up to 0.8 and 0.65 at 300 K for 1% intercalated and 1% substituted Bi2Te3, respectively. 相似文献
2.
L. P. Bulat I. A. Drabkin V. V. Karatayev V. B. Osvenskii Yu. N. Parkhomenko M. G. Lavrentev A. I. Sorokin D. A. Pshenai-Severin V. D. Blank G. I. Pivovarov V. T. Bublik N. Yu. Tabachkova 《Journal of Electronic Materials》2013,42(7):2110-2113
Ball milling with subsequent spark plasma sintering (SPS) was used to fabricate bulk nanothermoelectrics based on Bi x Sb2?x Te3. The SPS technique enables reduced size of grains in comparison with the hot-pressing method. The electrical and thermal conductivities, Seebeck coefficient, and thermoelectric figure of merit as functions of temperature and alloy composition were measured for different sintering temperatures. The greatest value of the figure of merit ZT = 1.25 was reached at the temperature of 90°C to 100°C in Bi0.4Sb1.6Te3 for sintering temperature of 450°C to 500°C. The volume and quantitative distributions of size of coherent dispersion areas (CDA) were calculated for different sintering temperatures. The phonon thermal conductivity of nanostructured Bi x Sb2?x Te3 was investigated theoretically taking into account phonon scattering on grain boundaries and nanoprecipitates. 相似文献
3.
Menglei Wu Yukun Xiao Zhengping Fu Zhixiang Li Jingtao Xu Jun Jiang Haochuan Jiang Gaojie Xu 《Journal of Electronic Materials》2014,43(9):3087-3091
CdTe compound is a prospective thermoelectric material due to its high Seebeck coefficient and low thermal conductivity. In the present study, we optimized its carrier concentration by substituting Cl on the Te site in order to improve the electrical conductivity and decrease the lattice thermal conductivity. The polycrystalline CdTe1?x Cl x (x = 0.005, 0.01, 0.03, 0.05) samples were fabricated by solid state reaction followed with spark plasma sintering, and the relative densities of the sintered samples were higher than 98%. Thermoelectric properties, including Seebeck coefficient (α), electrical conductivity (σ). and thermal conductivity (κ), were measured in the temperature range of 300–700 K. The increase of Cl content (x) caused an increase of σ, and the maximum ZT value of 0.2 was obtained at about 630 K for the CdTe0.97Cl0.03 sample. 相似文献
4.
Thermoelectric properties of the substitution system (Bi1?x Sb x )2S3 have been investigated, where binary Bi2S3 and Sb2S3 are narrow-gap semiconductors. It is confirmed that metallic conduction, originating from mobile electrons due to production of sulfur vacancies, is observed in Bi2S3 over a wide temperature range below room temperature. In Sb2S3, mobile carriers are not created and insulating behavior is observed because of the considerably wide bandgap. Change of the carrier number by substitution of antimony contributes strongly to the thermoelectric properties (resistivity and Seebeck coefficient). As a result, the nondimensional figure of merit, ZT, decreases monotonically with increasing antimony content. The maximum value of ZT is obtained in Bi2S3 as ZT ≈ 0.1 at room temperature. It is pointed out that control of the carrier number, which is achieved by production of sulfur vacancies, is important to achieve high thermoelectric performance in the (Bi1?x Sb x )2S3 system. It is possible that the thermoelectric efficiency could be improved by control of the carrier concentration in the bismuth-rich region, including pure binary Bi2S3. 相似文献
5.
Zhen Chen Min Zhou Rongjin Huang Chuanjun Huang Chunmei Song Yuan Zhou Laifeng Li 《Journal of Electronic Materials》2012,41(6):1725-1729
In this study, a series of Sn-doped (Bi85Sb15)1?x Sn x (x?=?0, 0.025, 0.05, 0.1, 0.2, 0.3) thermoelectric materials was fabricated through mechanical alloying followed by pressureless sintering. The crystal structure was characterized by x-ray diffraction. The electrical transport properties and thermal properties were measured in the temperature range from 77?K to 300?K. The electrical transport as a function of temperature appeared to be characteristic of a semimetal. The Seebeck coefficient gradually changed from negative to positive with increasing Sn doping, showing p-type electrical transport properties. It is found that the Seebeck coefficients of the p-type Bi-Sb alloys decrease with increasing dopant concentration of Sn, which may be due to increasing carrier concentration. Among the p-type alloys, the power factor of (Bi85Sb15)0.975Sn0.025 reached a maximum value of 1.3?×?10?3?W/mK2 at 265?K, and the optimum figure of merit value of 0.13 was obtained at 240?K. The results indicate that good p-type Bi-Sb alloys can be prepared by this synthesis procedure. 相似文献
6.
7.
A series of Zintl compounds Mg3Bi2-x Pn x (Pn = P and Sb) have been synthesized by the solid-state reaction method. While Sb can be substituted to a level as high as x = 1.0, P can be substituted only up to x = 0.5. The thermoelectric potential of these compounds has been evaluated by measuring resistivity (ρ), Seebeck (α) and Hall coefficients, and thermal conductivity between 80 K and 850 K. The measured resistivity and Seebeck coefficient values are consistent with those expected for small-bandgap semiconductors. Hall measurements suggest that the carriers are p type with concentration (p) increasing from ~1019 cm?3 to ~1020 cm?3 as the Bi content is increased. The Hall mobility decreases with increasing temperature (T) and reaches a more or less similar value (~45 cm2/V s) for all substituted compositions at room temperature. Due to mass defect scattering, the lattice thermal conductivity (κ L) is decreased to a minimum of ~1.2 W/m K in Mg3BiSb. The power factor (α 2/ρ) is found to be rather low and falls in the range 0.38 mW/m K2 to 0.66 mW/m K2. As expected, at a high temperature of 825 K, the total thermal conductivity (κ) of Mg3BiSb reaches an impressive value of ~1.0 W/m K. The highest dimensionless figure of merit (ZT) is realized for Mg3BiSb and is ~0.4 at 825 K. 相似文献
8.
Shinji Munetoh Makoto Saisho Takuya Oka Toshiko Osada Hideshi Miura Osamu Furukimi 《Journal of Electronic Materials》2014,43(6):2430-2434
We have synthesized n- and p-type clathrates Ba8?d Au x Si46?x?y with various Au contents (4.6 < x < 6.0) by arc-melting, annealing at 1173 K, and spark plasma sintering at 1073 K. The Au compositions found by wavelength-dispersive x-ray spectrometry for the synthesized samples were slightly lower than the nominal compositions. Ba7.8Au4.6Si41.4 and Ba7.7Au4.9Si41.1 samples showed n- and p-type conduction, respectively. According to the electron count (Ba2+)8Au(3?)5.33Si40.67, the clathrate composition with x = 5.33 is expected to be an intrinsic semiconductor. Our experimental results show that increase of the Au composition causes a transition from n-type to p-type conduction between x = 4.6 and 4.9. We have also calculated the band structures of the Ba8Au x Si46?x clathrate including a vacancy by ab initio calculation based on density functional theory with structure optimization. It was found that the vacancy behaves like an electron acceptor and the numbers of vacancies at 24k sites for the synthesized Ba8Au x Si46?x?y clathrates can be estimated as ~0.4 in a unit cell. 相似文献
9.
In the current study, novel hexagonal rods based on Bi0.4Sb1.6Te3 ingots dispersed with x amount of Se (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) in the form Bi0.4Sb1.6Se3x Te3(1?x) were synthesized via a standard solid-state microwave route. The morphologies of these rods were explored using field-emission scanning electron microscopy (FESEM). The crystal structure of the powders was examined by x-ray diffraction (XRD) analysis, which showed that powders of the 0.0 ≤ x ≤ 0.8 samples could be indexed to the rhombohedral phase, whereas the sample with x = 1.0 had an orthorhombic phase structure. The influence of variations in the Se content on the thermoelectric properties was studied in the temperature range from 300 K to 523 K. Alloying of Se into Bi0.4Sb1.6Te3 effectively caused a decrease in the hole concentration and, thus, a decrease in the electrical conductivity and an increase in the Seebeck coefficient. The maximal power factor measured in the present work was 7.47 mW/mK2 at 373 K for the x = 0.8 sample. 相似文献
10.
Yi Ma Waruna Wijesekara Anders E. C. Palmqvist 《Journal of Electronic Materials》2012,41(6):1138-1146
Thermoelectric thin films of the ternary compounds (Bi x Sb1?x )2Te3 and Bi2(Te1?y Se y )3 were synthesized using potentiostatic electrochemical deposition on gold-coated silicon substrates from aqueous acidic solutions at room temperature. The surface morphology, elemental composition, and crystal structure of the deposited films were studied and correlated with preparation conditions. The thermoelectric properties of (Bi x Sb1?x )2Te3 and Bi2(Te1?y Se y )3 films, i.e., Seebeck coefficient and electrical resistivity, were measured after transferring the films to a nonconductive epoxy support. (Bi x Sb1?x )2Te3 thin films showed p-type semiconductivity, and the highest power factor was obtained for film deposited at a relatively large negative potential with composition close to Bi0.5Sb1.5Te3. In addition, Bi2(Te1?y Se y )3 thin films showed n-type semiconductivity, and the highest power factor was obtained for film deposited at a relatively small negative potential, having composition close to Bi2Te2.7Se0.3. In contrast to Bi2Te2.7Se0.3 thin films, an annealing treatment was required for Bi0.5Sb1.5Te3 thin films to achieve the same magnitude of power factor as Bi2Te2.7Se0.3. Therefore, Bi2Te2.7Se0.3 thin films appear to be good candidates for multilayer preparation using electrochemical deposition, but the morphology of the films must be further improved. 相似文献
11.
Chanyoung Kang Hongchao Wang HeeJin Kim Sung-Jin Kim Woochul Kim 《Journal of Electronic Materials》2014,43(2):353-358
The thermoelectric properties of p-Na x Pb1?x Te0.85Se0.15, which possesses a high thermoelectric figure of merit due to band convergence, have been systematically investigated for increasing Na concentration (x = 0.01, 0.02, 0.03, 0.05, and 0.07) from room temperature to 773 K. For x values up to 0.03, the hole concentration increases with the Na concentration; however, for x ≥ 0.03, excess Na forms separate microstructures with needle- and plate-like shapes. At high concentrations (x = 0.05 and 0.07) both the number and size of these structures increase (over 10 μm). Differential scanning calorimetry identifies a phase change near 660 K in samples with x = 0.05 and 0.07, confirming the formation of microstructures; this phase change leads to a decrease in electrical resistivity. However, these microstructures do not significantly affect thermal transport, probably because they are too large to scatter phonons. The highest thermoelectric figure of merit, zT, value is 1.6, which is obtained at 760 K for x = 0.05, due to the low thermal conductivity and electrical resistivity. 相似文献
12.
Q.L. He Z. Qin J. Zhang F. Gao X. Hu H.Z. Song 《Journal of Electronic Materials》2014,43(5):1432-1435
The influence of Ba doping on the thermoelectric properties of Bi2?x Ba x Sr2 Co2O y (x = 0.00, 0.025, 0.05, 0.075, 0.10, 0.125, and 0.15) samples prepared by the solid-state reaction method was investigated from 333 K to 973 K. For the samples with x ≤ 0.075, the electrical resistivity decreased with increase of the Ba doping amount due to p-type doping and they exhibited metallic electrical conductivity behavior, whereas the samples with x ≥ 0.10 exhibited semiconductor-like electrical conductivity behavior. The Seebeck coefficients of all the samples decreased with increase of the Ba doping amount. The thermal conductivity first decreased for x ≤ 0.075, then increased with higher Ba doping amounts. As an overall result, the dimensionless figure of merit (ZT) of Bi1.925Ba0.075Sr2Co2O y reached the maximum value of 0.245 at 973 K, being 41% higher than that of the undoped sample. 相似文献
13.
Sin-Wook You Il-Ho Kim Soon-Mok Choi Won-Seon Seo Sun-Uk Kim 《Journal of Electronic Materials》2013,42(7):1490-1494
Mg2Si1?x Sn x (0 ≤ x ≤ 1) solid solutions have been successfully prepared by mechanical alloying and hot pressing as a solid-state synthesis route. All specimens were identified as phases with antifluorite structure. The electrical conduction changed from n-type to p-type at room temperature for x ≥ 0.5 due to the intrinsic properties of Mg2Sn. The absolute value of the Seebeck coefficient decreased with increasing temperature, and the electrical conductivity increased with increasing temperature; this is indicative of nondegenerate semiconducting behavior. The thermal conductivity was reduced by Mg2Si-Mg2Sn solid solution due to phonon scattering by the alloying effect. 相似文献
14.
In this work, hot-pressed pellets of the K2Bi8Se13 family of compounds were prepared for the first time. The pellet fabrication of selected members of the K2Bi8Se13?x S x series was studied. Sintering parameters, such as temperature, pressure, and duration, were investigated based on a statistical design- of-experiments approach to identify the optimum conditions for fabrication of high-quality pellets. These optimum conditions were then applied for the K2Bi8Se13?x S x series, and the thermoelectric properties of the stoichiometric members for x = 0, 4, 6, and 8 were studied. Doping experiments were also investigated using sulfur excess in the x = 6 member in an attempt to modify its properties. 相似文献
15.
Gen Li Junyou Yang Ye Xiao Liangwei Fu Jiangying Peng Yuan Deng Pinwen Zhu Haixue Yan 《Journal of Electronic Materials》2013,42(4):675-678
Starting from elemental powder mixtures of Fe x In4?x Se3 (x = 0, 0.05, 0.1, 0.15), polycrystalline In4Se3-based compounds with homogeneous microstructures were prepared by mechanical alloying (MA) and hot pressing (HP). With the increase of x from 0 to 0.15, the electrical resistivity and the absolute value of the Seebeck coefficient increased, while the thermal conductivity first decreased and then increased. The maximal dimensionless figure of merit ZT of 0.44 was obtained for the Fe x In4?x Se3 (x = 0.05) sample at 723 K. 相似文献
16.
Peng Gao Isil Berkun Robert D. Schmidt Matthew F. Luzenski Xu Lu Patricia Bordon Sarac Eldon D. Case Timothy P. Hogan 《Journal of Electronic Materials》2014,43(6):1790-1803
Mg2(Si,Sn) compounds are promising candidate low-cost, lightweight, nontoxic thermoelectric materials made from abundant elements and are suited for power generation applications in the intermediate temperature range of 600 K to 800 K. Knowledge on the transport and mechanical properties of Mg2(Si,Sn) compounds is essential to the design of Mg2(Si,Sn)-based thermoelectric devices. In this work, such materials were synthesized using the molten-salt sealing method and were powder processed, followed by pulsed electric sintering densification. A set of Mg2.08Si0.4?x Sn0.6Sb x (0 ≤ x ≤ 0.072) compounds were investigated, and a peak ZT of 1.50 was obtained at 716 K in Mg2.08Si0.364Sn0.6Sb0.036. The high ZT is attributed to a high electrical conductivity in these samples, possibly caused by a magnesium deficiency in the final product. The mechanical response of the material to stresses is a function of the elastic moduli. The temperature-dependent Young’s modulus, shear modulus, bulk modulus, Poisson’s ratio, acoustic wave speeds, and acoustic Debye temperature of the undoped Mg2(Si,Sn) compounds were measured using resonant ultrasound spectroscopy from 295 K to 603 K. In addition, the hardness and fracture toughness were measured at room temperature. 相似文献
17.
In this study we performed substitution experiments on the gallium site of the intermetallic semiconductor FeGa3, to adjust the charge carrier concentration, and determined the thermoelectric (TE) properties of the resulting products. Isoelectronic species aluminium and indium, hole-doping zinc, and electron-doping germanium were chosen to find suitable substituent elements. The samples FeGa3?x E x (E = Al, In, Zn, Ge; x = 0.03, 0.05, 0.06, 0.10, 0.20) were prepared by liquid–solid–reaction with subsequent spark plasma sintering treatment. X-ray diffraction, metallographic, and microstructure analysis were used to determine chemical composition and to evaluate the suitability of the substitution element. For solid solutions FeGa3?x Al x and FeGa3?x In x the substitution concentrations were very low (x ≤ 0.02) and did not improve the TE properties of FeGa3. The samples FeGa3?x Zn x had the expected p-type behaviour and slightly lower thermal conductivity than the binary compound. A substantial increase in the TE figure of merit was achieved for the solid solution FeGa3?x Ge x for which transition from semiconducting to metal-like behaviour was observed, with an additional decrease of thermal conductivity. The maximum ZT value of 0.21 was achieved for the composition FeGa2.80Ge0.20. 相似文献
18.
M. Søndergaard M. Christensen K. A. Borup H. Yin B.B. Iversen 《Journal of Electronic Materials》2013,42(7):1417-1421
Eleven samples of nominal composition Mg2.2Si0.9925?x Sn x Sb0.0075 with x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.9925 were prepared by induction melting, ball milling, and spark plasma sintering. Hall effect, resistivity, Seebeck coefficient, and thermal conductivity measurements were conducted from room temperature to 400°C. Six of the samples were investigated for thermal stability by measuring powder x-ray diffraction while heating to 400°C. All samples were stable in air during the ~12-h-long data collection, except for Mg2.2Sn0.9925Sb0.0075, which showed development of an elemental Sn phase after heating. The lattice parameter of each sample was extracted through Rietveld refinement and revealed a linear dependency on nominal composition. Measurement of top and bottom of the pellets exhibited systematic differences in lattice parameter and Seebeck coefficient, indicating that stoichiometry gradients are created during sintering. 相似文献
19.
Toshimichi Nakayama Ken Kurosaki Masaaki Shuto Chang-eun Kim Yuji Ohishi Hiroaki Muta Shinsuke Yamanaka 《Journal of Electronic Materials》2013,42(7):1719-1724
GaSb is a promising thermoelectric material that exhibits good electrical properties. However, it has a high lattice thermal conductivity (κ lat). Nanostructured bulk materials have been attracting interest because they effectively scatter phonons, significantly reducing κ lat. AgPb m SbTe m+2 (LAST-m) compounds have recently been reported to have low κ lat. These compounds have a NaCl structure, similar to that of binary PbTe, where Ag and Sb occupy the Pb site. In these compounds, two divalent Pb atoms are replaced with a monovalent Ag atom and a trivalent Sb atom to maintain charge compensation. In the present study, we reduced κ lat of GaSb by applying the same principle as in LAST-m. Specifically, we substituted Te for Sb and generated vacancies at the Ga site to maintain charge compensation. This produced compounds with chemical compositions of (GaSb)3(1?x)(Ga2Te3) x (x = 0, 0.05, 0.10, and 0.25), where GaSb and Ga2Te3 both have the zincblende crystal structure. We employed two different annealing conditions: annealing at 833 K followed by quenching, and annealing at 833 K followed by cooling to room temperature over 3 days. The former annealed samples with compositions of x = 0.05 and 0.10 had nanoscale Ga-rich precipitates and exhibited a large reduction in κ lat. 相似文献
20.
NingYu Wu Tim C. Holgate Ngo Van Nong Nini Pryds Søren Linderoth 《Journal of Electronic Materials》2013,42(7):2134-2142
Ca3Co4O9+δ samples were synthesized by solid-state (SS) and sol–gel (SG) reactions, followed by spark plasma sintering under different processing conditions. The synthesis process was optimized and the resulting materials characterized with respect to their microstructure, bulk density, and thermoelectric transport properties. High power factors of about 400 μW/m·K2 and 465 μW/m·K2 (at 800°C) were measured for SS and SG samples, respectively. The improved thermoelectric performance of the SG sample is believed to originate from the smaller particle sizes and better grain alignment. The SG method is suggested to be a beneficial means of obtaining high-performance thermoelectric materials of Ca3Co4O9+δ type. 相似文献