定向生长Bi2Te3-Sb2Te3三元合金热电材料的组织与性能

利用Bridgman定向凝固法,在大凝固速率范围内5～1000μm/s制备出Bi2Te3-Sb2Te3三元合金块体热电材料,并对其凝固组织和不同凝固速率下合金的热电性能进行研究。结果表明:高温度梯度和大凝固速率范围内制备的25%Bi2Te3-75%Sb2Te3合金定向凝固组织由Bi0.5Sb1.5Te3单相组织组成;在较低凝固速率5μm/s下,熔体生长平界面失稳形成胞状组织,而随定向凝固速率的增加,胞状组织减少,组织细化。不同定向凝固速率下25%Bi2Te3-75%Sb2Te3合金的Seebeck系数和电阻率随着凝固速率的增加而增大。50μm/s下300～450K范围内获得功率因子(PF)在4.6×10-3～5.01×10-3W/(K2.m),并在350K时PF值达到最大值5.01×10-3W/(K2.m);而在高凝固速率500μm/s下,其功率因子也可达4.5×10-3W/(K2.m),表明高温度梯度和大凝固速率制备热电材料是一种有效的制备工艺方法。     

Gamma Irradiation Effects in InBi_(0.8) Te_(0.2) Crystals Grown by Horizontal Directional Freezing

The high-energy gamma-ray irradiation treatment using Co-60 isotope offers the possibility of engineering mechanical and optoelectronic properties of In Bi0.8Te0.2crystals. Tellurium-doped indium bismuthide(In Bi) crystals were prepared by horizontal directional freezing technique. Dose-dependent modifications in structure, composition and surface topographical features have been analyzed by X-ray powder diffraction, X-ray energy-dispersive analysis, transmission electron and atomic force microscopy, respectively. Dielectric constant and dielectric loss were found to increase with the cumulative dose of radiation, and a shift in the ferroelectric transition temperature(Tc) from 405 to 410 K was observed for25 k Gy. Upon irradiation, there is an enhancement in microhardness(HV), yield stress(ry) and stiffness constant(C11).The optical transmittance was decreased by 12.45%, resulting in a reduction in the optical band gap from 0.210 e V to0.198 e V. These results indicate the suitability of In Bi0.8Sb0.2crystals for low-wavelength infrared applications.     

Thermoelectric properties of Bi_(0.5)Sb_(1.5)Te_3/polyaniline composites prepared by mechanical blending and in-situ polymerization

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Ga、K双掺杂P型Bi_(0.5)Sb_(1.5)Te_3材料的制备及热电性能

采用真空熔炼和热压方法制备了Ga和K双掺杂Bi0.5Sb1.5Te3热电材料。XRD结果表明,Ga0.02Bi0.5Sb1.48-x Kx Te3块体材料的XRD图谱与Bi0.5Sb1.5Te3的XRD图谱对应一致,但双掺杂样品的衍射峰略微向左偏移。热压块体材料中存在明显的(00l)晶面择优取向。SEM形貌表明材料组织致密且有层状结构特征。Ga和K双掺杂可使Bi0.5Sb1.5Te3在室温附近的Seebeck系数有一定的提高,而双掺杂样品的电导率均得到了不同程度的提高,其中Ga0.02Bi0.5Sb1.42K0.06Te3样品的电导率得到较明显的改善。在300~500 K测量温度范围内,所有双掺杂样品的热导率高于Bi0.5Sb1.5Te3的热导率,在300 K附近双掺杂样品的ZT值得到提高,其中Ga0.02Bi0.5Sb1.42K0.06Te3样品在300 K时ZT值达到1.5。     

Electric and mechanical performances of Bi0.5Sb1.5Te3 prepared by spark plasma sintering

Thermoelectric (TE) materials are a kind of functional materials which can be used to convert directly heat energy to electricity or reversely.The thermoelectric effects hold great potential for application in power generation and refrigeration.Bi2Te3 and its alloys are well known as best TE materials currently available near room temperature.This paper studies respectively the effects of spark plasma sintering (SPS) on electric performance of Bi0.5Sb1.5Te3 thermoelectric materials that are prepared through vacuum melting and ball milling.Through X-ray Diffraction and cold field emission scanning electric microscope s4800, the phase constituent and microstructure of the TE materials samples were analyzed.Electric conductivity and power factor can be improved with the rise of Spark Plasma Sintering temperature (from 300 to 500 ℃) and pressure(from 30 to 60 MPa), and the density and mechanical strength of Bi0.5Sb1.5Te3 thermoelectric material increase, too.     

添加Sb的Ga2Te3合金热电性能

本研究采用等摩尔分数的Sb元素替换Ga2Te3中的Ga元素,并利用放电等离子烧结技术制备Ga1.9Sb0.1Te3合金,研究其微观结构和热电性能。结果表明,添加Sb元素后,材料的Seebeck系数为130～240μV/K,明显低于单晶Ga2Te3,电导率为3600～1740??1·m?1,至少是单晶Ga2Te3的17倍,热导率提高近25%。在649K时Ga1.9Sb0.1Te3合金的热电优值(ZT)达到最大值0.1,是同温度下单晶Ga2Te3ZT值的3倍。     

The lead-zirconium system: binary phases and a series of interstitial compounds of the host Zr5Pb3

The Pb-Zr system contains the phases Zr_5.8Pb (Cr₃Si-type), Zr₅Pb₃ (Mn₅Si₃) and Zr₅Pb₄ (Ti₅Ga₄). Zr₅Pb₄ has a substoichiometric region above approximately 800°C, extending to about Zr₅Pb_3.65 at 1000°C. Reactive powder sintering in sealed Ta containers at 1000–1350°C is the most effective route for the synthesis of pure phases of both the binaries and the interstitial derivatives Zr₅Pb₃Z. Twenty examples of the latter were obtained with Z — Al, Si, P, S, Fe, Co, Ni, Cu, Zn, Ga, Gc, As, Sc, Ag, Cd, In, Sn, Sb, Te, (Pb), (second period Z were not investigated). Single crystals for Z — Al, Cd, Zb, Pb_0.87, Pb_0.94 were obtained by metal flux or vapor phase transport reactions, and the last three were quantified by X-ray crystallography. Volume trends as a function of group and period follow metal/covalent radii trends for Z fairly well.     

Effects of hot pressing on electric performances of Bi0.5Sb1.5Te3

The effects of hot pressing on electric performance and mechanical strength of Bi0.5Sb1.5Te3 thermoelectric material prepared through vacuum melting and milling were studied. The phase constituent and microstructure were analyzed by X-ray Diffraction and cold field emission Scanning Electric Microscope. Aeolotropisms of the material on microstructure and electric performances are approved. With the rise of hot pressing temperature (from 300-500 ℃) and pressure (30-70 Mpa), electric conductivity and power factor are improved. Moreover, Bi0.5Sb1.5Te3 material can gain ideal thermoelectric performances and increased mechanical strength by hot pressing.     

急冷甩带过程和过量Te对p型Bi0.5Sb1.5Te3化合物热电性能的影响

采用感应熔炼制备得到了P型Bi0.5 Sb1.5Te3+x％(质量)Te(x=0、2、4和6)合金.将合金均匀分成R和S两组,R组不作处理,S组通过急冷甩带过程获得厚度约为5～15 μm的薄带,然后将两组样品分别粉碎过筛后,热压烧结成块体材料.利用扫描电镜(SEM)观察了薄带和烧结块体的形貌结构,在室温下测量其电性能....     

Isothermal section of the Pt–Sb–Te system at 1000 °C

The phase relations in the system Pt–Sb–Te have been investigated at 1000 °C, using sealed glass capsule techniques. The reaction products have been studied by reflected light microscopy, X-ray diffraction, and electron probe microanalysis. At 1000 °C, Pt, PtSb, PtSb₂, Pt₃Te₄, and PtTe₂ are the stable solid phases. There are two liquid phase fields: a large field extends across the ternary system from the Pt–Sb join to the Pt–Te join, the other as a thin strip near the Sb–Te join. PtSb becomes Pt-poor up to 3 at.% from stoichiometry as substitution of Te for Sb and Pt increases. PtSb₂ and PtTe₂ exhibit the largest solid solution range among the solid phases present.     

纳米BaTiO3复合Cu1.8S块体的热电性能和力学性能研究

Cu_1.8S作为一种P型半导体热电材料,具有环境友好、原料丰富、价格低廉等优点而受到广泛关注。本研究采用机械合金化(Mechanical Alloying, MA)结合放电等离子烧结(Spark Plasma Sintering, SPS)工艺制备了一系列Cu_1.8S-x wt%BaTiO₃ (x =0,0.075,0.1,0.15,0.2)块体材料,研究了复合纳米BaTiO₃对Cu_1.8S的相结构、微观形貌、热电性能及力学性能的影响。结果表明,纳米BaTiO₃的加入不影响Cu_1.8S的相结构、晶胞参数和载流子浓度;纳米BaTiO₃均匀分布在Cu_1.8S基体的晶界处产生钉扎效应进而细化晶粒并产生气孔。Cu_1.8S-0.2 wt%BaTiO₃样品在773 K时获得最低的热导率2.2 Wm^_-1K^_-1,所有样品的ZT值基本保持不变约0.39 (773 K)。同时Cu_1.8S-x wt%BaTiO₃块体样品的维氏硬度由82 (x = 0)增加到87 (x = 0.2)。本研究表明在Cu_1.8S中复合纳米BaTiO₃可以在不影响材料热电性能的前提下有效提升块体样品的力学性能,为后续Cu-S体系热电性能和力学性能的协同提升提供了思路,有利于制备高机械性能且稳定耐用的Cu-S体系的热电器件。     

凝固条件和熔体处理对ZL101合金组织和力学性能的影响

探讨了不同凝固条件、不同变质剂、Ti-B细化剂以及不同浇注温度对ZL101合金组织和性能的影响,结果表明,快速冷却能提高合金的抗, 冷能提高塑性;Sb、Sb-Te、RE、Sb-Te-RE变质均能使共晶Si变细、变小,使合金的抗拉强度提高,其中Sb-Te变质的效果最佳;在Sb-Te-RE三元变质的基础上,加入Ti-B复合盐能细化晶粒,但缩（气）也同增大,使其性能恶,且发现高的浇注温度有助于提高用这种方法处理的合金的力学性能。     

SPS法制备的三元合金Ag0.405Sb0.532Te的热电性能

采用放电等离子烧结法(SPS)制备了三元合金Ag0.405Sb0.532Te,并研究了它的输运性能,即Seebeck系数、电导率和热导率。结果表明,当温度从316K上升到548K时,电导率从7.6×104S·m-1下降到6.6×104S·m-1。在438K以上,热导率随温度上升逐渐增加,低于438K时,热导率趋于稳定,约为0.86W·(K·m)-1。无量纲热电优值ZT在548K时取得最大值0.65,稍高于Ag0.365Sb0.558Te三元合金的0.61。与掺Ag的AgxBi0.5Sb1.5-xTe3(x=0～0.4)合金相比,热电性能得到了改善。并再次讨论了AgxBi0.5Sb1.5-xTe3合金中析出的第二相Ag-Sb-Te三元合金的作用机制。     

沉积温度对Ge2Sb2Te5溅射薄膜结构、电/光性质的影响

在衬底加热条件下利用磁控溅射法制备Ge2Sb2Te5薄膜,利用X射线衍射仪表征各种沉积温度下薄膜的结构,差示扫描量热法(DSC)确定的薄膜晶化温度为168℃(加热升温速率为5℃/min)。用四探针法测试薄膜的方块电阻,分光光度计测试薄膜的反射率谱,并根据反射率数据讨论在波长为405和650nm时薄膜的反射率对比度同沉积温度关系。结果表明:室温沉积的薄膜为非晶态;在衬底温度为140℃条件下薄膜已完全转变为晶态Ge2Sb2Te5,在300℃时出现少量的六方相;低于140℃时易形成非Ge2Sb2Te5组分的其它晶相,它们对薄膜的电/光性质有很大的影响,可能是导致此类相变光存储薄膜使用过程中反射率对比度下降的原因。     

定向凝固Ag掺杂Mg3Sb2合金热电性能

通过定向凝固方法可以高效制备Mg₃Sb₂晶体,根据凝固理论计算了平界面生长临界速率,在此速率下可以有效抑制第二相Sb的析出。对不同的凝固速率下的Mg₃Sb₂晶体微观组织进行了分析,表明凝固速率为5μm·s^-1时可以有效减少Mg空位的出现,并在晶体中获得过量Mg原子,有利于更好地提升热电性能。通过消除晶界和Ag元素掺杂有效提升了Mg₃Sb₂晶体的载流子迁移率和浓度,在测试温度区间(300～800K)内,最大电导率值可达309S·cm^-1,同时保持了较高的Seebeck系数值,从而获得了更好的电子传输性能(PF_max=1.2mW·m^-1·K^-2),通过Hall测试和第一性原理计算对此结果进行了验证。Ag掺杂浓度为2.5at%下相应的热电优值最高可以达到0.67,此方法为Mg₃Sb₂基热电材料性能优化提供了新的...     

Effect of antimony on vigorous interfacial reaction of Sn-Sb/Te couples

A vigorous reaction between molten Sn-Sb solder and Te substrate leads to a thick SnTe-Sn mixture layer at the soldered junction. The effect of Sb addition in Sn on the kinetics of Sn-Sb/Te interfacial reaction and formation of SnTe-Sn reaction layer is reported. Sb element was found to expedite the growth of SnTe-Sn reaction layer in the Sn-Sb/Te couples dramatically. With increasing Sb content in Sn-Sb solder, the growth rate of SnTe-Sn reaction layer increases while both the size of SnTe grains and the fraction of Sn in SnTe-Sn decrease. The thickness of SnTe-Sn layer follows a parabolic law with reaction time for Sn-Sb/Te couples, unlike the linear dependence with time for Sn/Te couples. An apparent diffusivity of 2 × 10⁻⁷ cm²/s was determined for Sn transport through the SnTe-Sn layer in the Sn-Sb/Te couples reacting at 250 °C.     

The preparation,characterization and physical properties of SbCl5-doped polyacetylene

Trans-polyacetylene has been doped with SbCl₅ to molar concentrations varying between y = 0.005 and y = 0.12. Physical characterization was accomplished by employing ¹³C solid-state MAS n.m.r., d.c. conductivity, i.r. and ¹²¹Sb Mössbauer spectroscopy; all experiments being performed on a unique sample of the appropriate concentration.The results demonstrate two distinct concentration regions. For samples with y < 0.05, the conductivity increases with increasing y; ¹²¹Sb Mössbauer spectroscopy unequivocally demonstrates only the presence of SbCl₃. The charge transfer counterion is concluded to be Cl^?, since the presence of Sb (+5) (SbCl₅, SbCl₆^?, Sb₂Cl₁₀^?) as well as of SbCl₄^? can be ruled out.For samples with y > 0.07, Mössbauer spectra show the presence of both Sb (+5) and Sb (+3); the conductivity decreases with increasing y. I.r. spectroscopy and ¹³C n.m.r. consistently demonstrate CCl bond formation in this concentration range.     

Electrical behaviors for growth of LAST alloys using vapor phase deposition

The well-dispersed crystal structures of LAST (Lead Antimony Silver Tellurium) alloys grown by a vapor phase deposition method are demonstrated to have excellent electrical characteristics in this study. The atomic ratio of Pb to Te in the alloys are kept at 0.85-0.88. The distribution of component concentrations depends on the deposition temperature, and the Ag- and Sb-rich segments are fabricated at high deposition temperature. Experimental data suggest that the higher Sb content in the crystal increases carrier concentration up to ∼10¹⁹ (per cm). The electrical behavior of the crystal is n-type under Sb doping, and it was transferred into p-type once the samples are dominated by Ag doping, which also raises the mobility to a level as high as ∼10³ cm²/V. Test results of this study have indicated that both Ag and Sb elements contribute to the electrical conductivity enhancement, however, an excess amount of Ag may significantly deteriorate the electrical performance instead.     

ACRT-Te溶液Bridgman法生长的In掺杂CdMnTe界面研究(英文)

采用ACRT-Te溶液垂直布里奇曼法成功制备出直径为30mm、长度为60mm的CdMnTe晶锭。相对于普通布里奇曼法生长的CdMnTe晶锭,Te溶液法生长的 CdMnTe晶锭中的孪晶大大减少。但是由于较高的Te夹杂相密度,红外透过成像显示晶锭生长界面的微观形貌既不均匀也不规则。同时,采用激光共聚焦显微镜也观察到CdMnTe富Te区存在无规律沉积的含有孔洞的不规则形状Te相。如果采用合适的生长工艺得到较为平直的生长界面,Te溶液垂直布里奇曼法可以有效减少CdMnTe晶体中的孪晶。     

Dislocations in Plastically Bent Germanium Crystals

Densities and distributions of dislocations in plastically bent germanium crystals before and after annealing were studied. In the bent and annealed crystals, the theoretical relationship between radius of curvature and density of dislocations \(\left( {\rho = \frac{1}{{r\overrightarrow b }}} \right)\) is confirmed. Before annealing, however, more dislocations are present than required, and these are distributed with a minimum at the neutral axis and maxima at the top and bottom surfaces. On annealing, three significant changes occur in the bent bars: 1) the average dislocation density is reduced, presumably by the annihilation of opposite signs; 2) dislocations migrate from the high density outside regions toward the low density neutral axis, thus producing the equilibrium distribution of dislocations; and 3) a polygonized structure is formed by movement of the dislocations into walls normal to the slip plane.