K、Al共掺杂Bi0.5Sb1.5Te3热电材料的制备及性能

采用真空熔炼及热压方法制备了K和Al共掺杂P型Bi0.5Sb1.5Te3热电材料。XRD分析结果表明,K0.04Bi0.5Sb1.5-x Alx Te3块体材料的XRD图谱与Bi0.5Sb1.5Te3的图谱完全对应,SEM形貌分析表明材料具有一定的层状结构和微孔。K和Al共掺杂提高了Bi0.5Sb1.5Te3在室温附近的Seebeck系数。除了K0.04Bi0.5Sb1.34Al0.12Te3样品的300K和400K以上的高温区,以及共掺杂样品的500K高温附近之外,K和Al共掺杂均使Bi0.5Sb1.5Te3材料的电导率降低。在300~500K温度范围内,K0.04Bi0.5Sb1.42Al0.04Te3样品的热导率均小于Bi0.5Sb1.5Te3的热导率。在300~350K温度范围内,K0.04Bi0.5Sb1.42Al0.04Te3样品的热电优值较Bi0.5Sb1.5Te3有较大幅度的提高。     

K、Al共掺杂Bi_2 Te_(2.7) Se_(0.3)热电材料的制备及性能研究

采用真空熔炼和热压烧结技术制备了K和Al共掺杂Bi2Te2.7Se0.3热电材料。利用X射线衍射(XRD)、扫描电子显微镜(SEM)对样品的物相结构和表面形貌进行了表征。XRD分析结果表明,K0.04Bi1.96-x Al x Te2.7Se0.3块体材料的XRD图谱与Bi2Te2.7Se0.3的XRD图谱对应一致,SEM形貌表明材料组织致密且有层状结构特征。K0.04Bi1.92-Al0.04Te2.7Se0.3合金提高了材料的Seebeck系数,K0.04Bi1.88Al0.08Te2.7Se0.3和K0.04Bi1.84Al0.12Te2.7Se0.3大幅度提高了材料的电导率,通过K和Al部分替代Bi,使材料的热导率有不同程度的减小,在300~500 K温度范围内,K和Al共掺杂均较大幅度地提高了Bi2Te2.7Se0.3的热电优值。     

Na、Ga共掺杂对n型Bi_2Te_(2.7)Se_(0.3)电热输运性能的影响

采用真空熔炼及热压烧结方法制备了Na和Ga共掺杂n型Bi2Te2.7Se0.3热电材料。XRD结果表明,Na0.04Bi1.96-xGaxTe2.7Se0.3块体材料的XRD图谱与Bi2Te2.7Se0.3的图谱对应一致。通过EDAX技术对Na0.04Bi1.96-xGaxTe2.7Se0.3块体材料的成分进行了分析,无氧化现象。在298~523K温度范围内,在垂直于热压方向对样品的电热输运性能进行了测试分析,结果表明Na和Ga共掺杂可以有效地提高Bi2Te2.7Se0.3的载流子浓度,从而使电导率得到明显改善,但同时Seebeck系数有不同程度的损失。由于晶格热导率减小,Na掺杂及共掺杂样品Na0.04Bi1.96-xGaxTe2.7Se0.3(x=0.04)均使热导率降低。当Na掺杂浓度为0.04时,随着Ga掺杂浓度的增加,热导率呈现递增的现象,Na和Ga共掺杂样品Na0.04Bi1.96-xGaxTe2.7Se0.3(x=0.04)的热电优值获得了较明显的提高,在398K时的最大ZT值为0.75。     

机械球磨-热压法制备Bio.5Sb1.5Te3热电材料

用机械球磨-热压法制备了Bi0.5Sb1.5Te3热电材料,分别研究了机械球磨时间对合成Bi0.5Sb1.5Te3合金相的影响和烧结温度对其热电性能的影响.结果表明Bi、Sb、、Te原始混合粉末高能球磨10 h以后,就可以完全合金化,生成Bi0.5Sb1.5Te3相.球磨10h的粉末分别在400、450和520℃下热压烧结成型,烧结样品的密度随烧结温度的增大而增加,Seebeck系数和电阻率随烧结温度的升高而降低     

Ag-Bi-Sb-Te四元合金的热电性能

以Ag、Bi、Sb、Te为原料在1373K真空熔炼合成了AgxBi0.5Sb1.5-xTe3(x=0～0.5)合金.微观组织和结构分析显示,真空熔炼的合金具有层状组织特征,属R3m晶体结构,当x≥0.2时出现面心立方AgSbTe2相.电学性能测试表明,在300～580K温度范围内合金的电导率随温度升高而下降,掺Ag后合金的电导率明显提高,掺Ag量为x=0.1试样的最大值达到2.3×105S/m.材料的Seebeck系数均为正值,表明掺Ag合金为p型半导体.     

稀土掺杂对锡基Half-Heusler合金热电特性的影响

采用电弧熔炼法和放电等离子体烧结法,制备了稀土掺杂的金属间化合物Zr1-xLaxNiSn(x=0.05,0.1,0.15,0.2,0.3,0.4)和Zr0.98R0.02NiSn0.98X0.02(R=La,Ce;X=Sb,Bi).用X射线衍射仪分析研究了它们的晶体结构随稀土替代量演化的规律.在室温到700K的范围内,对其热电特性进行了评价.研究结果表明,代换量x小于0.15时,稀土原子可以进入晶格形成单相化合物.代换量x大于0.15的样品中含有非half-Heusler的第二相,且含量随x增大而增加.少量稀土掺杂可以有效地降低材料的热导率而保持良好的电输运特性.在575K,Zr0.98La0.02NiSn0.98Sb0.02的热电优值达到0.5.     

Yb掺杂Ⅷ型Yb_xBa_(8-x)Ga_(16)Sn_(30)笼合物的制备及热电性能

本研究采用Sn熔剂法成功制备出Yb掺杂Ⅷ型笼合物Yb_xBa_(8-x)Ga_(16)Sn_(30)(0≤x≤2)热电材料,通过测试其电导率、Seebeck系数和Hall系数等分析材料的电性能,并估算其ZT值。结果表明:掺入Yb后材料的晶格常数随Yb含量的增加而减小。x=1.5样品的电导率在整个测试温度范围内均比其余样品高相比x=0的样品,其电导率提高了约60%,这是由于在载流子迁移率相当的情况下该样品拥有较高的载流子浓度。此外在300～583 K范围内,样品的电导率随温度的升高而降低表现出重掺杂半导体特性;而在583 K以后,电导率随温度的升高而增大,表现出半导体特性。在测试温度范围内(300～600 K),所有样品的Seebeck系数绝对值均随温度的升高先增大后降低。在所有样品中,x=1.5的样品具有最高的电导率,其在489 K时获得最大功率因子为2.43×10~(-3) W/(m·K~2)在此温度下其ZT值为1.35。     

NaxCo2O4基复合材料的制备及其热电性能

采用固相反应法制备出NaxCo2O4(x=0.9,1.1,1.3)多晶氧化物,采用水热法制备出(Bi0.1Sb0.9)2Te3单相粉末材料,再用球磨法将二者均匀混合获得了复合材料(Bi0.1Sb0.9)2Te3/NaxCo2O4。在5～300K的温度范围内,利用综合物性测试系统(PPMS)对热压复合材料的热电性能进行测量与评价。实验结果表明复合材料的热导率显著降低,同时电导率增大,与NaxCo2O4相比,复合材料的热电性能获得了显著提高。在室温下,复合材料的热电优值ZT约为3.5×10-4。热电性能的改善源于复合材料界面的声子散射的增强。     

SPS法制备Bi_2Te_3基热电合金的热电性能

用粉末冶金工艺结合SPS烧结制备了p型(Bi0.2Sb0.8)2Te3和n型Bi2(Te0.975Se0.025)3多晶半导体合金,研究烧结工艺对其热电性能的影响.结果表明,室温下,p型(Bi0.2Sb0.8)2Te3材料的热电优值Z为3.25×10<'-3K<'-1,n型Bi2(Te0.975Se0.025)3材料的热电优值Z为2.21×10<'-3K<'-1.     

MA-SPS制备高热电性能p型(Bi,Sb)2Te3合金块体

机械合金化与放电等离子烧结技术(SPS)相结合制备了p型(Bi,Sb)2Te3合金块体.在300～423K的温度范围内测试了样品的电导率﹑Seebeck系数和热导率.系统研究了球磨时间对合金化与热电性能的影响.球磨2h的样品具有最低的热导率,因此其ZT值最高,在323K时为1.16,在373K达到最大值1.23.     

Microstructures and thermoelectric properties of p-type pseudo-binary AgxBi0.5Sb1.5−xTe3 (x = 0.05–0.4) alloys prepared by cold pressing

The p-type pseudo-binary Ag_xBi_0.5Sb_1.5−xTe₃ (x = 0.05–0.4) alloys were prepared by cold pressing. The thermal conductivities (κ) were calculated from the values of heat capacities, densities and thermal diffusivities measured, and range approximately from 0.66 to 0.56 (W K^− 1 m^− 1) for the Ag_xBi_0.5Sb_1.5−xTe₃ alloy with molar fraction x being 0.4. Combining with the electrical properties obtained in the previous study, the maximum dimensionless figure of merit ZT of 1.1 was obtained at the temperature of 558 K.     

Selective Dissolution-Derived Nanoporous Design of Impurity-Free Bi2Te3 Alloys with High Thermoelectric Performance

Thermoelectric technology, which has been receiving attention as a sustainable energy source, has limited applications because of its relatively low conversion efficiency. To broaden their application scope, thermoelectric materials require a high dimensionless figure of merit (ZT). Porous structuring of a thermoelectric material is a promising approach to enhance ZT by reducing its thermal conductivity. However, nanopores do not form in thermoelectric materials in a straightforward manner; impurities are also likely to be present in thermoelectric materials. Here, a simple but effective way to synthesize impurity-free nanoporous Bi_0.4Sb_1.6Te₃ via the use of nanoporous raw powder, which is scalably formed by the selective dissolution of KCl after collision between Bi_0.4Sb_1.6Te₃ and KCl powders, is proposed. This approach creates abundant nanopores, which effectively scatter phonons, thereby reducing the lattice thermal conductivity by 33% from 0.55 to 0.37 W m⁻¹ K⁻¹. Benefitting from the optimized porous structure, porous Bi_0.4Sb_1.6Te₃ achieves a high ZT of 1.41 in the temperature range of 333–373 K, and an excellent average ZT of 1.34 over a wide temperature range of 298–473 K. This study provides a facile and scalable method for developing high thermoelectric performance Bi₂Te₃-based alloys that can be further applied to other thermoelectric materials.     

Preparation and characterization of segmented stacking for thermoelectric power generation

Based on the Seebeck effect, thermoelectric generators can convert thermal energy directly into electrical power, which can be applied in waste heat recovery and clean energy generation. In this work, segmented thermoelectric legs were prepared with high-performance thermoelectric materials for the fabrication of multistage thermoelectric generators, which can be utilized in medium temperature energy harvesting. The P-type leg material was Pb_0.94Sr_0.04Na_0.02Te/Bi_0.5Sb_1.5Te₃, and the N-type leg material was Pb_0.94Ag_0.01La_0.05Te/Bi₂Te₃. The length ratio of the two segments was optimized based on the energy conversion efficiency under different working conditions. The segmented legs were measured with the four-probe method at different temperatures to evaluate their output performance. At a temperature difference of 420 K, the maximum output power density was 0.40 W/cm² for the P-type leg and 0.32 W/cm² for the N-type leg.     

Enhanced thermoelectric properties in Co4Sb12 − xTex alloys prepared by HPHT

Skutterudite compounds Co₄Sb_12 ? xTe_x with bcc crystal structure were prepared by high pressure and high temperature (HTHP) method. The study explored chemical doping with Te at the Sb site in an attempt to optimize the thermoelectric figure of merit ZT in the system Co₄Sb_12 ? xTe_x. The electrical resistivities, Seebeck coefficients and thermal conductivities of the samples were measured in the temperature range of 300–710 K. We found that the presence of Te substantially decreased the electrical resistivity without any detrimental effect on the Seebeck coefficients, which improved the power factor. Among all the samples, Co₄Sb_11.5Te_0.5 shows the highest power factor of 35.3 µw/(cmK²) at 710 K, and the maximum ZT value reaches 0.67 at 710 K.     

快淬和球磨时间对p型(Bi_(0.25)Sb_(0.75))_2Te_3合金热电性能的影响

通过快淬-机械球磨-放电等离子烧结工艺制备了p型(Bi0.25Sb0.75)2Te3块体热电材料.在300~523K温度范围内对其电导率、Seebeck系数和热导率进行了测试,并系统研究了快淬后球磨时间对合金热电性能的影响.研究结果表明,随着球磨时间的延长,样品的电导率呈先降后升的趋势,Seebeck系数变化并不明显,而热导率随球磨时间的延长逐渐下降.球磨20h的样品在室温下具有最高的热电优值,最大值达到0.96,机械抗弯强度达到91MPa.     

Thermoelectric Properties of (Bi2Te3)1 ? x ? y(Sb2Te3)x(Sb2Se3)y Single Crystals

Homogeneous and graded n- and p-type (Bi₂Te₃)_{1 − x − y} (Sb₂Te₃) _x (Sb₂Se₃) _y crystals are grown by the Czochralski technique with melt supply through a floating crucible. The dimensionless thermoelectric figure of merit of the n- and p-type crystals is ZT = 1.1 (350 K) and 1.0 (375 K), respectively. It is shown that (Bi₂Te₃)_{1 − x − y} (Sb₂Te₃) _x (Sb₂Se₃) _y pseudoternary solid solutions can be used to produce monolithic n- and p- type graded and segmented thermoelectric materials by Czochralski growth. The thermoelectric power distribution across the seed-crystal interface is studied using scanning hot microprobe measurements. __________ Translated from Neorganicheskie Materialy, Vol. 41, No. 10, 2005, pp. 1186–1193. Original Russian Text Copyright ? 2005 by Svechnikova, Shelimova, Konstantinov, Kretova, Avilov, Zemskov, Stiewe, Zuber, Muller.     

Hydrothermal synthesis and thermoelectric properties of nanostructured Bi0.5Sb1.5Te3 compounds

Single-phase Bi_0.5Sb_1.5Te₃ compounds have been prepared by hydrothermal synthesis at 150 °C for 24 h using SbCl₃, BiCl₃ and tellurium powder as precursors. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) have been applied to analyze the phase distributions, microstructures and grain sizes of the as-grown Bi_0.5Sb_1.5Te₃ products. It is found that the hydrothermally synthesized Bi_0.5Sb_1.5Te₃ nanopowders have a morphology dominated by irregular hexagonal sheets due to the anisotropic growth of the crystals. The Bi_0.5Sb_1.5Te₃ nanosheets are parallelly stacked in certain direction to form sheet-agglomerates attribute to the temperature gradients in the solution.     

Introduction of porous structure: A feasible and promising method for improving thermoelectric performance of Bi2Te3 based bulks

The porous p-type Bi_0.4Sb_1.6Te₃ bulks containing irregularly and randomly oriented pores were obtained by artificially controlling the relative density of sintered samples during resistance pressing sintering process. It is demonstrated that the thermoelectric performances are significantly affected by the porous structure, especially for the electrical and thermal conductivity due to the enhanced carrier scattering and phonon scattering. The increasing porosity resulted in the obvious decrease in electrical and thermal conductivity, and little change in Seebeck coefficients. It is encouraging that the reduction of thermal conductivity can compensate for the deterioration of electrical performance, leading to the enhancement in thermoelectric figure of merit (ZT). The maximum ZT value of 1.0 was obtained for the sample with a relative density of 90% at 333?K. Unfortunately, the increase in porosity also brought in obvious degradations in Vickers hardness from 51.71 to 27.74?HV. It is worth mentioning that although the Vickers hardness of the sample with a relative density of 90% decreased to 40.12?HV, it was still about twice as high as that of the zone melting sample (21.25?HV). To summarize, introducing pores structure into bulks properly not only enhances the ZT value of Bi₂Te₃ based alloys, but also reduces the use of raw materials and saves production cost.     

Thermoelectric properties of the tetradymite-type Bi2Te2S-Sb2Te2S solid solution

The thermoelectric properties of the tetradymite-type Bi_2−xSb_xTe₂S solid solution (0 ≤ x ≤ 2) are reported for the temperature range 5-300 K. The properties of non-stoichiometric, Cl and Sn doped n- and p-type variants are reported as well. The Seebeck coefficients for these materials range from −170 to +270 μV K⁻¹ while the resistivities range from those of semimetals, 2 mΩ cm, to semiconductors, >1000 mΩ cm. Thermal conductivities were low for most compositions, typically 1.5 W m⁻¹ K⁻¹. Nominally undoped Bi₂Te₂S shows the highest thermoelectric efficiency amongst the tested materials with a ZT = 0.26 at 300 K that decreased to 0.04 at 100 K. The crystal structure of Sb₂Te₂S, a novel tetradymite-type material, is also reported.     

Phase diagram and thermoelectric properties of Ag3−x Sb1+x Te4 system

In order to obtain better thermoelectric performance in the composition domain should be stabilized, the phase diagram of the Ag_3–x Sb_1+x Te₄ system by varying the Ag:Sb ratio. The phase diagram is investigated using the differential thermal analysis and the powder X-ray diffraction techniques. The Seebeck coefficient and the electrical resistivity of the grown bulk crystals of the system are also measured. The phase diagram of the Ag_3–x Sb_1+x Te₄ system indicates that a mixed phase of AgSbTe₂ and Ag₂Te, which is expected to show higher thermoelectric performance, exists in a wide temperature range between 600 and 830 K at a composition of Ag_2.2Sb_1.8Te₄. The maximum of Seebeck coefficient for AgSbTe₂ (x = 1) is 0.73 mV/K at about 680 K. The thermoelectric performance is lowered by the compositional deviation from Ag:Sb:Te = 1:1:2.