熔体旋甩工艺对n型InSb化合物的微结构及热电性能的影响

采用新颖的熔体旋甩结合放电等离子烧结技术制备了单相InSb化合物,研究了熔体旋甩工艺对其微结构以及热电性能的影响. 结果表明,熔体旋甩得到的薄带自由面主要由300 nm—2 μm的小柱状晶组成,薄带接触面为非晶或精细纳米晶,薄带经烧结后得到了具有大量层状精细纳米结构的致密块体,尺寸约为40 nm. 与熔融+放电等离子体烧结制备样品相比,在测试温度范围内（300—700 K）,试样的电导率略有下降,但Seebeck系数显著增加,热导率和晶格热导率显著降低,室温下晶格热导率降低幅度约为106%,700 K下晶格热导率的降低幅度达1664%,熔融+熔体旋甩+放电等离子体烧结制备的InSb化合物试样在700 K时其最大ZT值达到049,与熔融+放电等离子体烧结试样相比提高了29%.     

熔体旋甩工艺对Zn掺杂Ⅰ-型Ba8Ga12Zn2Ge32笼合物微结构及热电性能的影响

采用新颖的熔体旋甩(MS)结合放电等离子烧结(SPS)技术制备了单相Zn掺杂的I-型Ba8Ga12Zn2Ge32笼合物,研究了熔体旋甩工艺对其微结构以及热电性能的影响.结果表明,MS得到的薄带自由面主要由300 nm-1 μm的小立方体单晶组成,薄带经SPS烧结后得到了具有大量层状精细结构的致密块体.与熔融+SPS工艺制备的试样相比,熔融+MS+SPS制备的Ba8Ga12Zn2Ge3笼合物室温载流子浓度增加而迁移率降低,在测试温度范围内,试样的电导率略有下降,Seebeck系数增加,热导率和晶格热导率显著降低,900 K时其晶格热导率从1.06 W/mK降低至0.42W/mK.熔融+MS+SPS制备的Ba8Ca12Zn2Ge32笼合物试样在900 K时其最大ZT值达到0.90,与熔融+SPS试样相比提高了75%.     

熔体旋甩工艺对Zn掺杂Ⅰ-型Ba8Ga12Zn2Ge32笼合物微结构及热电性能的影响

采用新颖的熔体旋甩(MS)结合放电等离子烧结(SPS)技术制备了单相Zn掺杂的Ⅰ-型Ba₈Ga₁₂Zn₂Ge₃₂笼合物,研究了熔体旋甩工艺对其微结构以及热电性能的影响. 结果表明,MS得到的薄带自由面主要由300nm—1μm的小立方体单晶组成,薄带经SPS烧结后得到了具有大量层状精细结构的致密块体. 与熔融+SPS工艺制备的试样相比,熔融+MS+SPS制备的Ba₈Ga₁₂Zn 关键词： 熔体旋甩 Ⅰ-型笼合物 热电性能     

熔体旋甩法制备p型填充式方钴矿化合物Ce0.3Fe1.5Co2.5Sb12的微结构及热电性能

采用熔体旋甩法结合放电等离子烧结技术(MS-SPS)制备了p型填充式方钴矿化合物Ce_0.3Fe_1.5Co_2.5Sb₁₂,研究了熔体旋甩工艺对微结构以及热电性能的影响规律.结果表明,较高的铜辊转速和较低的喷气压力有利于提高熔体的冷却速率,使带状产物晶粒细化.薄带经SPS烧结后得到致密、基本单相、晶粒尺寸均匀细小(150—300 nm)的块体.与传统方法制备的试样相比,MS-SPS试样虽然电导率有所降低,但因具有较大的Se 关键词： 熔体旋甩 p型填充式方钴矿化合物 微结构 热电性能     

In掺杂对n型方钴矿化合物的微结构及热电性能的影响规律

用熔融退火法结合放电等离子烧结(SPS)技术成功制备了具有不同 In含量的In_xCo₄Sb₁₂(x=0.1—0.4)方钴矿化合物.X射线衍射分析和扫描电镜分析结果表明,当In的掺杂量超过一定值时,化合物中会原位析出纳米InSb的第二相,且其含量会随In掺杂量的增加而增大.研究结果表明,InSb第二相的存在增大了化合物的功率因子,降低了化合物的晶格热导率,显著提高了化合物的热电性能.在温度为800 K时,In相似文献   

纳米结构碲化铋合金的制备及电热输运特性

采用惰性气体保护蒸发-冷凝法制备了纳米Bi及Te粉末, 结合机械合金化和放电等离子烧结技术, 在不同烧结温度下制备出了单一物相且具有纳米层状结构及孪晶亚结构的n型Bi₂Te₃块体材料, 并系统研究了块体材料的晶粒尺度、微结构及其对电热传输特性的影响. SEM, TEM分析结果表明, 以纳米粉末为原料, 通过有效控制工艺条件, 可以制备出具有纳米层状结构Bi₂Te₃合金块体材料, 同时纳米层状结构中存在孪晶亚结构; 热电性能测试结果表明, 具有纳米层状结构及孪晶亚结构的块体试样与粗晶材料相比, 热导率大幅度降低, 在423 K附近, 热导率由粗晶材料的1.80 W/mK降至1.19 W/mK, 晶格热导率从1.16 W/mK降至0.61 W/mK, 表明纳米层状结构与孪晶亚结构共存, 有利于进一步提高声子散射, 降低晶格热导率. 其中在693 K放电等离子烧结后的试样于423K附近取得最大值的无量纲热电优值(ZT), 达到0.74.     

晶粒尺寸对CoSb3化合物热电性能的影响

系统地研究了晶粒尺寸对CoSb3化合物热电性能的影响规律,结果表明晶粒尺寸对CoSb3化合物的晶格热导率κp、电导率σ、能隙宽度Eg和Seebeck系数α有显著影响.当晶粒尺寸由微米尺度减小到纳米尺度时,晶格热导率κp显著降低,Seebeck系数α有较大幅度的增加,能隙宽度Eg变宽,电导率σ有一定程度的下降.平均晶粒尺寸为200nm的CoSb3化合物在温度为700K时,ZT值达到0.43,比平均晶粒尺寸为5000 nm的试样增加了4倍.     

Zn掺杂P型Ba8Ga16ZnxGe30-x笼合物的合成及热电性能

用熔融法结合放电等离子烧结方法合成了Zn掺杂单相p型Ge基Ⅰ型笼合物Ba8Ga16ZnxGe30-x(x=3,4,5,6),探索Zn取代Ge对其热电性能的影响规律,结果表明:所制备的Ba8Ga16ZnxGe30-x化合物为p型传导,随Zn取代量x的增加,化合物室温载流子浓度Np逐渐增加,室温载流子迁移率μH和电导率逐渐降低.在所有试样中,Ba8Ga16Zn3Ge27化合物的Seebeck系数α在300—870K内始终最大,温度为300K时Seebeck系数为234μV/K,在700K附近达295μV/K.化合物的热导率随Zn取代量x的增加而降低.Ba8Ga16Zn3Ge27化合物在806K最大ZT值达0.38.     

高压烧结对n型PbTe基材料热电性能的影响

 采用高压烧结技术制备了按偏离化学计量比配制的PbTe基热电材料（Pb_0.55Te_0.45），重点研究了烧结压力对材料热电性能的影响。研究结果表明：高压烧结过程能有效降低材料中的晶格缺陷，从而显著改变样品中的载流子浓度及其迁移率。与未经烧结的常压熔融样品相比，高压烧结样品的Seebeck系数得到大幅提高，电导率略有降低，室温热导率降低了50%，所以高压烧结样品的品质因子得到较大提高。当烧结压力为2 GPa时，所得样品在700 K时其品质因子达到0.59，相比未经烧结的常压熔融样品提高了150%。     

非化学计量比AgSbTe2+x化合物制备及热电性能

采用高纯元素直接熔融、淬火并结合放电等离子烧结方法制备了非化学计量比AgSbTe_2+x(x=0—0.05)系列样品,研究了不同Te含量在300—600 K范围内对样品热电性能的影响规律.结果表明:随着Te含量的增加,Ag⁺离子空位浓度增加,空穴浓度和电导率大幅度提高,Seebeck系数减小.热导率随Te过量程度的增加略有增加,但所有Te过量样品的晶格热导率均介于0.32—0.49 W/mK之间,低于化学计量比样品的值,接近理论最低晶格热导率.AgS 关键词： 2')" href="#">AgSbTe₂ 非化学计量比 热电性能 热导率     

Structure and thermoelectric properties of nanocomposite bismuth telluride prepared by melt spinning or by partially alloying with IV–VI compounds

Bismuth telluride samples are compared with respect to the evolution of their thermoelectric material parameters like thermal and electrical conductivity. The Seebeck coefficient is discussed in dependence on the melt spinning fabrication technique. The melt spinner used is only able to produce small thin ribbon shaped specimens, some as thin as 10 μm. This limits melt spinning to mainly production of research specimens for alloys with high critical cooling rate, which are difficult to fabricate with other techniques. Additional parameters are alloying or doping of the base material by comparing the properties as prepared to different annealing conditions. The intrinsic p‐ and n‐doped material was alloyed with up to 0.5% lead telluride by rapidly cooling the bulk material to improve the thermoelectric properties analysed from RT up to about 600 K. A Seebeck coefficient of well above 200 µV/K could be obtained for p‐ and n‐type materials. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Quick preparation and thermal transport properties of nanostructured β-FeSi2 bulk material

This paper reports that the nanostructured β-FeSi2 bulk materials are prepared by a new synthesis process by combining melt spinning(MS) and subsequent spark plasma sintering(SPS).It investigates the influence of linear speed of the rolling copper wheel,injection pressure and SPS regime on microstructure and phase composition of the rapidly solidified ribbons after MS and bulk production respectively,and discusses the effects of the microstructure on thermal transport properties.There are two crystalline phases(α-Fe2Si5 and ε-FeSi) in the rapidly solidified ribbons;the crystal grains become smaller when the cooling rate increases(the 20 nm minimum crystal of ε-FeSi is obtained).Having been sintered for 1 min above 1123 K and annealed for 5 min at 923 K,the single-phase nanostructured βFeSi2 bulk materials with 200-500 nm grain size and 98% relative density are obtained.The microstructure of β-FeSi2 has great effect on thermal transport properties.With decreasing sintering temperature,the grain size decreases,the thermal conductivity of β-FeSi2 is reduced remarkably.The thermal conductivity of β-FeSi2 decreases notably(reduced 72% at room temperature) in comparison with the β-FeSi2 prepared by traditional casting method.     

Hydrogen adsorption on a clean palladium ribbon; Thermal desorption and work function measurements

The adsorption of hydrogen on a palladium ribbon has been studied by thermal desorption and work function measurements. It has been established that several heating cycles of the sample covered with hydrogen, up to 700 K lead to the repeated appearance of hydrogen thermal desorption peaks. Analogous experiments of adsorption and repeated heating cycles up to 700 K have shown work function changes decrease to zero as a result of heating and an increase again almost up to the initial value following cooling, in a much shorter time than that required for adsorption. The experimental results show that only a small part of the adsorbed hydrogen is desorbed in the temperature range of the thermal desorption peak. The major part of adsorbed hydrogen penetrates below the surface which leads to a nonequilibium increase of the bulk concentration.     

Effect of Ga alloying on thermoelectric properties of InSb

As a potential thermoelectric (TE) material, the high lattice thermal conductivity and relatively low weighted mobility severely limit TE property optimization of InSb binary compound. In this paper, we substituted In of InSb with Ga and systematically investigated the effect of Ga alloying on the Seebeck coefficient, electrical conductivity and lattice thermal conductivity of InSb between 300 K and 770 K. We found that Ga alloying simultaneously reduced the lattice thermal conductivity and optimized the weighted mobility of InSb. The lattice thermal conductivity has been analyzed using Abeles model to gain more insight on the roles of Ga in In_1-xGa_xSb(x = 0, 0.1, 0.15, 0.2) solid solution. The synergetic effect of Ga alloying on the electron and phonon transport leads to a marked enhancement in TE potential of InSb. The dimensionless figures of merit of InSb and In_0.8Ga_0.2Sb reach, respectively, 0.54 and 0.52 at 770 K.     

The Structure and Magnetic Properties of Fe-Cu-Nb-Si-B/Fe-Nb-Si-B Bilayer

We have investigated the structure (by TEM and SEM) and basic surface and bulk magnetic properties (by measurement of surface and bulk hysteresis loop and domain structure observations) of a Fe-Cu-Nb-Si-B/Fe-Nb-Si-B bilayer prepared by melt spinning method. We have detected perfect bonding between the two layers of the bilayered ribbon. This bonding produces tangential stress, which influences magnetic properties measured in surface layers at both sides of the ribbon.     

Effects of rapid thermal annealing on the morphology and optical properity of ultrathin InSb film deposited on SiO2/Si substrate

Ultrathin InSb thin films on SiO₂/Si substrates are prepared by radio frequency (RF) magnetron sputtering and rapid thermal annealing (RTA) at 300, 400, and 500℃, respectively. X-ray diffraction (XRD) indicates that InSb film treated by RTA at 500℃, which is higher than its melting temperature (about 485℃), shows a monocrystalline-like feature. High-resolution transmission electron microscopy (HRTEM) micrograph shows that melt recrystallization of InSb film on SiO₂/Si(111) substrate is along the (111) planes. The transmittances of InSb films decrease and the optical band gaps redshift from 0.24 eV to 0.19 eV with annealing temperature increasing from 300℃ to 500℃, which is indicated by Fourier transform infrared spectroscopy (FTIR) measurement. The observed changes demonstrate that RAT is a viable technique for improving characteristics of InSb films, especially the melt-recrystallized film treated by RTA at 500℃.     

Magnetoresistance and exchange bias in high Mn content melt-spun Mn_(46)Ni_(42)Sn_(11)Sb_1 alloy ribbon

Highly textured Heusler alloy Mn_(46)Ni_(42)Sn_(11)Sb_1 ribbons were prepared by melt spinning. The annealed high Mn content Mn46Ni42Sn11Sb1 ribbon cross-section microstructure, crystal structure, martensitic transformation(MT), and magnetoresistance(MR) properties were investigated. The MR in the annealed ribbon was assessed by the magnetic field direction perpendicular to the ribbon surface with the magnetic field up to 30 k Oe. The large negative value of 25% for MR was obtained at 244 K. The exchange bias(EB) effects of the as-spun and annealed ribbons were investigated. After annealing, the EB effects have been improved by about 25 Oe at the temperature of 50 K. The magnetizations have increased approximately by 10% more than the as-spun ribbon.