(Bi2Te3)0.90(Sb2Te3)0.05(Sb2Se3)0.05熔炼冷压烧结材料的制备及其热电性能的研究

本文采用熔炼冷压烧结法制备了n型赝三元(Bi2Te3)0.90(Sb2Te3)0.05(Sb2Se3)0.05熔炼冷压烧结热电材料,分析了材料的微观结构并测试了材料的热电性能.研究表明:烧结有利于提高材料的热电性能;n型赝三元熔炼冷压烧结热电材料的热电性能沿垂直于冷压压力方向存在优化取向.     

不同表面活性剂制备n型Bi2Te3热电材料

分别使用P123(聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物)、PVP(聚乙烯吡咯烷酮)和EDTA(乙二胺四乙酸)为模板剂采用水热法合成n型Bi2 Te3热电纳米粉体,通过放电等离子烧结技术(简称SPS)将粉体烧结成块体样品.利用XRD、SEM、ZEM-3以及激光导热仪等对制备的样品进行物相、形貌及热电性能表征.结果显示:三种模板剂制备的Bi2 Te3纳米颗粒大部分呈片状,其中PVP制备的纳米片最为规整,EDTA制备的纳米片大小不均一,P123制备的纳米片夹杂有棒状和团聚饼状的形貌;XRD表征显示所制备粉体均为纯Bi2 Te3相,没有其它杂质.对块体样品的热电性能研究发现:由于Bi2 Te3具有独特的层状结构,会对载流子和声子的传输产生影响,造成所制备块体样品垂直于压力方向的ZT值要大于平行于压力方向的ZT值;采用PVP模板剂制备Bi2 Te3样品的热电性能最高,在温度为480 K时,ZT值达到0.33.     

Pb0.92Sr0.08-xBax(Sb2/3Mn1/3)0.05Zr0.48Ti0.47O3的制备与性能研究

采用传统固相烧结法制备了Pb0.92Sr0.08-xBax(Sb2/3 Mn1/3)005Zr0.48Ti0.47O3(PSBSM-PZT)压电陶瓷样品.研究了不同Sr2+、Ba2+掺杂含量对样品的相结构、微观形貌、压电和介电性能的影响.结果显示:所有样品均为钙钛矿结构.而当x=0.02～0.06时,陶瓷样品组分位于准同型相界区(MPB).由于位于准同型相界区域的陶瓷样品对于电畴的转向具有促进作用,所以处于MPB区域的陶瓷样品具有较大的压电和介电性能,但同时由于电畴转向带来的较大内摩擦和结构损耗,从而提高了材料的机械损耗和介电损耗.当x=0.02时的陶瓷样品获得最佳的综合性能:d33=346 pC/N,kp=0.58,Qm=1217,εr=1724,tanδ=0.774;.     

Ca3-xCexCo4O9+δ陶瓷的制备与电输运性能

采用柠檬酸溶胶-凝胶法制备了掺Ce的钴酸钙(Ca3Co4O9+δ)陶瓷,通过TG-DSC、XRD和SEM对样品进行表征,研究了Ce掺杂对电导率、Seebeck系数和功率因子的影响。结果表明:陶瓷样品的断面形貌呈片层状。随着Ce掺杂量的增加,样品的导电机制发生变化,测试温度范围内样品的电导率和功率因子下降,Seebeck系数先增加后下降。     

AgNW s/Yb0.3Co4Sb12纳米复合热电材料的制备及热电性能的研究

采用多元醇法和熔融淬火高温退火法合成银纳米线(AgNWs)和填充方钴矿Yb0.3Co4Sb12材料,采用超声分散法并结合等离子体快速烧结技术(SPS)烧结成AgNWs/Yb0.3 Co4 Sb12纳米复合材料.通过XRD和扫描电镜分析材料的物相结构与微观形貌,测量计算了不同AgNWs复合含量样品的电导率、Seebeck系数、热导率、晶格热导率和ZT值.发现了复合AgNWs可以很大程度地提高方钴矿材料的电输运性能,但也使得其热导率不可避免地升高.最终AgNWs复合含量为0.5wt;的复合材料热电性能最佳,达到850 K时的1.02.     

烧结温度和升温速率对Pb(Sb1/3Mn2/3)0.05Zr0.47Ti0.48O3压电陶瓷性能的影响

采用传统固相法制备了Pb(Sb1/3 Mn2/3)0.05Zr0.47Ti0.48 O3 (PMS-PZT)压电陶瓷.利用XRD、SEM和EDS等研究PMS-PZT陶瓷体系在烧结过程中形成的过渡液相和形成过渡液相温度(1100℃)附近的升温速率对陶瓷结构、压电和介电性能的影响.结果表明:不同烧结温度下,所有样品均为单一的钙钛矿四方相,过渡液相不会对相的结构有影响,但是当烧结温度较低时,过渡液相在烧结后期以玻璃相在晶界附近富集,对陶瓷的压电和介电性能有很大影响.随着烧结温度和升温速率的升高,PMS-PZT晶粒尺寸增大,晶粒均匀性和规则性得以改善,晶化质量得到提高;d33测试和阻抗分析测试结果表明PMS-PZT样品在1100℃附近以7 ℃·min-1升温速率并在1250℃烧结时具有最好的压电和介电性能:d33 =313 C/N,kp=0.59,Qm=1481,εr=1437,tanδ=0.53;.     

一步水热法制备钠离子电池正极材料Na3V2(PO4)2F3及其性能研究

采用一步水热法制备了钠离子电池正极材料Na3V2(PO4)2F3,用XRD、SEM、恒流充放电等对样品进行了表征.研究表明,络合剂种类对Na3V2(PO4)2F3的结构、形貌及电化学性能有重大影响,以抗坏血酸、柠檬酸、草酸和酒石酸为络合剂制备的样品分别为小立方体、球形、大立方体和不规则球状,除以酒石酸为络合剂制备的样品为无定形结构外,其余样品均结晶良好.其中以抗坏血酸为络合剂制备的样品结晶度最高且电化学性能最优,该样品在0.05 C和0.5C倍率下的首次放电比容量为112.0 mAh/g和92.5 mAh/g,且具有良好的倍率性能和循环性能.     

不同形貌Sb2O3的控制合成及其光催化性能研究

采用醇解法与水热法制备了Sb2O3光催化材料,研究了制备条件对Sb2O3晶型、形貌及催化性能的影响.结果表明,以PEG-400为表面活性剂、反应体系pH=7时,通过醇解法制得的立方晶型、呈球形颗粒状的Sb2O3催化性能最佳,在紫外光照180 min时,对10.0 mg/L罗丹明B的降解率达到了96.8;;对20.0 mg/L左氧氟沙星降解率为66.3;;对10.0 mg/L磺胺吡啶降解率为46.2;.当反应温度为160℃,反应时间为12 h时,由水热法制得的斜方晶型、呈枕头状的Sb2O3催化性能较差,在紫外光照射180 min时,对10.0 mg/L罗丹明B的降解率为57;.     

ZnO过渡层对Au/Hg3In2Te6肖特基接触特性的影响研究

利用脉冲激光沉积技术在Hg3In2Te6晶体表面制备ZnO过渡层,并对ZnO过渡层进行了表征.结合X射线光电子能谱深度剖析对ZnO/Hg3In2Te6界面元素的化合态进行研究,并通过半导体参数分析仪对Au/ZnO/Hg3In2Te6肖特基接触电学特性进行测试.研究结果表明,采用本实验条件可在Hg3In2Te6晶体表面获得结晶度高、表面粗糙度低,且沿(002)晶面择优生长的ZnO过渡层.同时,ZnO过渡层的引入使Au/Hg3In2Te6肖特基接触的漏电流降低一个数量级,势垒高度提高6.5;.这种现象可能是由于ZnO/Hg3In2Te6界面存在的互扩散使O原子占据了Hg原子空位,从而降低耗尽层中能级缺陷而引起.     

Sb2O3掺杂BiFeO3-BaTiO3压电陶瓷的结构及电性能研究

采用传统固相烧结法合成了0.7BiFeO₃-0.3BaTiO₃+x%Sb₂O₃(质量分数)陶瓷(BFO-BTO+xSb, x=0.00~0.20),研究了Sb₂O₃掺杂对BFO-BTO陶瓷的晶相结构、介电、导电以及压电和铁电性能的影响,并对影响机理进行探讨。结果表明:Sb掺杂导致陶瓷的晶体结构由伪立方相向菱形相转化。Sb的B位取代增加了BFO-BTO+xSb陶瓷的铁电弛豫性,降低高温损耗,并使居里温度T_c有所降低。导电特性的研究表明,Sb掺杂改变了$V_O^×$和Fe²⁺的浓度,降低了电导率,但没有改变陶瓷的导电机制,其主要载流子是氧空位。Sb掺杂量x=0.05时,BFO-BTO+xSb陶瓷表现出最佳的综合电性能:d₃₃=213 pC/N,k_p=28.8%,Q_m=38,T_c=520 ℃,P_r =24.7 μC/cm²。     

Enhancement of thermoelectric efficiency in vapor deposited Sb2Te3 and Sb1.8In0.2Te3 crystals

Pure and indium doped antimony telluride (Sb₂Te₃) crystals find applications in high performance room temperature thermoelectric devices. Owing to the meagre physical properties exhibited on the cleavage faces of melt grown samples, an attempt was made to explore the thermoelectric parameters of p‐type crystals grown by the physical vapor deposition (PVD) method. The crystal structure of the grown platelets (9 mm× 8 mm× 2 mm) was identified as rhombohedral by x‐ray powder diffraction method. The energy dispersive analysis confirmed the elemental composition of the crystals. The electron microscopic and scanning probe image studies revealed that the crystals were grown by layer growth mechanism with low surface roughness. At room temperature (300 K), the values of Seebeck coefficient S (⊥ c) and power factor were observed to be higher for Sb_1.8In_0.2Te₃ crystals (155 μVK⁻¹, 2.669 × 10⁻³ W/mK²) than those of pure ones. Upon doping, the thermal conductivity κ (⊥ c) was decreased by 37.14% and thus thermoelectric efficiency was improved. The increased figure of merit, Z = 1.23 × 10⁻³ K⁻¹ for vapour grown Sb_1.8In_0.2Te₃ platelets indicates that it could be used as a potential thermoelectric candidate.     

Characterization of Ag-Doped Bi1.5Sb0.5Te3 Single Crystals

Single crystals of Bi_1.5Sb_0.5Te₃ doped with Ag atoms (c_Ag = 0 - 4.34x10¹⁹ atoms/cm³) were characterized by measurement of Hall coefficient, electrical conductivity, Seebeck coefficient and the figure of merit. It was found that Ag atoms in the crystal structure of Bi_1.5Sb_0.5Te₃ behave like donors. It is necessary to add more than one Ag atom to the Bi_1.5Sb_0.5Te₃ compound in order to suppress the hole concentration by one hole. Such a behaviour of the dopant is explained by the formation of various structural defects. Besides the dominant interstitial defects of Ag* silver atoms form also positively charged substitutional defects Ag″, Ag′, and a four-layer-lamellae of the type [Ag_0.5Sb_0.5]-Te-[Ag_0.5Sb_0.5]-Te. The incorporation of Ag atoms into the Bi_1.5Sb_0.5Te₃ lattice, besides the suppression of the hole concentration, leads to a decrease in the figure of merit Z.     

Bi掺杂对Ca3-xBixCo4O9氧化物微观结构和热电性能的影响

采用固态反应法制备Ca3-xBixCo4O9 (0.0≤x≤0.45)样品,并研究了Bi掺杂对样品的微观结构和热电性能的影响.XRD与SEM结果显示,在含Bi样品中形成了c轴取向的结构,x=0.3和x=0.45样品具有大的晶粒取向度和晶粒尺寸,这就导致了这两个样品具有较高的电导率.由于Bi3+替代Ca2+降低了载流子浓度,样品的塞贝克系数随Bi含量的增加而增加.在1000 K,x=0.3样品的功率因子可达2.77×10-4 W/m·K2,这一数值与利用热压法制备的Ca3Co4O9样品的功率因子相当.     

Material characteristics of metalorganic chemical vapor deposition of Bi2Te3 films on GaAs substrates

Metal organic chemical vapor deposition has been investigated for growth of Bi₂Te₃ films on (0 0 1) GaAs substrates using trimethylbismuth and diisopropyltelluride as metal organic sources. The results of surface morphology, electrical and thermoelectric properties as a function of growth parameters are given. The surface morphologies of Bi₂Te₃ films were strongly dependent on the deposition temperatures. Surface morphologies varied from step-flow growth mode to island coalescence structures depending on deposition temperature. In-plane carrier concentration and electrical Hall mobility were highly dependent on precursor's ratio of VI/V and deposition temperature. By optimizing growth parameters, we could clearly observe an electrically intrinsic region of the carrier concentration at the temperature higher than 240 K. The high Seebeck coefficient (of −160 μVK⁻¹) and good surface morphology of this material is promising for Bi₂Te₃-based thermoelectric thin film and two-dimensional supperlattice device applications.     

Evolution of growth and enhancement in power factor of InSb bulk crystal

Indium antimonide crystals were synthesized from the respective component elements using the vertical Bridgman technique. The grown crystals were characterized by using X-ray analysis, EDX, electrical conductivity and thermoelectric power measurements. The calculated structural parameters for the prepared crystal have a good agreement with the standard values. Crystallite size (D) of the obtained InSb crystals was calculated to be 62.4 nm. The measurements reveal higher values for Seebeck coefficient, electrical conductivity and power factor than the published results for the same compound.     

N型赝三元机械合金化冷压烧结热电材料的制备及其性能

本文采用机械合金化法成功制备了N型赝三元(Bi2Te3-Sb2Te3-Sb2Se3)合金粉体材料,该材料颗粒均匀、细小,颗粒尺寸在10～100nm量级.在此基础上采用冷压烧结法制备了N型赝三元机械合金化冷压烧结热电材料.研究了这种热电材料的电导率、塞贝克系数与烧结温度的关系.     

Electrophysical and structural-sensitive properties of liquid In2Te3 with 3d metal admixtures

Temperature dependencies of the electrical conductivity (up to 1700 K), thermoelectric power (up to 1700 K) and shear viscosity (up to 1150 K) of the liquid semiconducting alloy In₂Te₃ with 3d metal admixtures were investigated. It was shown that small amounts (up to 3%) of Ti, V, Fe, Ni increase the electrical conductivity and slightly affect the thermoelectric power values. All the admixtures decrease the viscosity. The In₂Te₃ is regarded as a double-structured melt with a low-temperature loose-packing structure with crystalline features and a high-temperature dense-packing metallic structure. A melting process implies a structure rearrangement from the short-range structure with a spatial covalent bonds distribution to the more dense-packed structure of the linear chain type. The impurity d-states are manifested in the sp-d hybridization phenomenon.     

Thermoelectric properties of Tl‐doped Bi2Se3 single crystals

The single crystals of the ternary system based on Bi_2‐xTl_xSe₃ (nominaly x = 0.0‐0.1) were prepared using the Bridgman technique. Samples with varying content of Tl were characterized by the measurement of lattice parameters, electrical conductivity σ_⊥c , Hall coefficient R_H (B∥c), and Seebeck coefficient S (ΔT ⊥c). The measurements indicate that by incorporating Tl in Bi₂Se₃ one lowers the concentration of free electrons and enhances their mobility. This effect is explained in terms of the point defects in the crystal lattice – formation of substitutional defects thallium on the site of bismuth Tl_Bi and the decrease of concentration of selenium vacancies V_Se⁺². We also discuss the temperature dependence of the power factor σS² of the samples. Upon the thallium doping we observe a significant increase of the power factor compare to the parental Bi₂Se₃. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)