Improvement in thermoelectric properties of an n-type bismuth telluride (Bi2Se0.3Te2.7) due to texture development and grain refinement during hot deformation

Hot deformation of an n-type bismuth telluride (nBT of composition Bi₂Se_0.3Te_2.7) results in a texture characteristic of the deformation mode. Extruded nBT has a fiber texture with ?112?0? directions aligned with the extrusion direction. Rolling of previously textured (extruded) and untextured (sintered powder compact) material results in a rolling texture with the basal plane parallel to the rolling plane, and the ?112?0? directions randomly oriented on the rolling plane. Results indicate an improvement in thermoelectric figure of merit at 300 K from 0.79 in the as-received extruded material to 0.93 in the rolled material.     

Efficiency simulations of thin film chalcogenide photovoltaic cells for different indoor lighting conditions

Photovoltaic (PV) energy is an efficient natural energy source for outdoor applications. However, for indoor applications, the efficiency of PV cells is much lower. Typically, the light intensity under artificial lighting conditions is less than 10 W/m² as compared to 100-1000 W/m² under outdoor conditions. Moreover, the spectrum is different from the outdoor solar spectrum. In this context, the question arises whether thin film chalcogenide photovoltaic cells are suitable for indoor use. This paper contributes to answering that question by comparing the power output of different thin film chalcogenide solar cells with the classical crystalline silicon cell as reference. The comparisons are done by efficiency simulation based on the quantum efficiencies of the solar cells and the light spectra of typical artificial light sources i.e. an LED lamp, a “warm” and a “cool” fluorescent tube and a common incandescent and halogen lamp, which are compared to the outdoor AM 1.5 spectrum as reference.     

碲化亚铜沉淀工艺优化及生产实践

介绍了铜阳极泥预处理碲化亚铜渣沉淀工艺优化和改进方法。探索试验结果表明,采用"碲化亚铜渣还原—铜粉置换"新工艺,碲沉淀率由90%提高至98%以上,铜粉用量由理论量2倍降至1.35倍。应用实践证明,该工艺综合经济效益显著,可实现溶液中碲的高效回收。     

Transverse magnetoresistance peculiarities of thermoelectric Lu-doped Bi2Te3 compound due to strong electrical disorder

The n-type thermoelectric Bi_1.9Lu_0.1Te₃ was prepared by microwave-solvothermal method and spark plasma sintering. The magnetic field and temperature dependences of transverse magnetoresistance measured within temperature 2–200 K interval allow finding the peculiarities characteristic for strongly disordered and inhomogeneous semiconductors. The first peculiarity is due to appearance of linear-in-magnetic field contribution to the total magnetoresistance reflected in a crossover from quadratic magnetoresistance at low magnetic fields to linear magnetoresistance at high magnetic fields. The linear magnetoresistance can result from the Hall resistance picked up from macroscopically distorted current paths due to local variations in stoichiometry of the compound studied. The second peculiarity is that both linear magnetoresistance magnitude and crossover field are functions of carrier mobility which is in agreement with the Parish and Littlewood model developed for disordered and inhomogeneous semiconductors. An increase in the mobility due to a decrease in temperature is accompanied by an increase in the magnetoresistance magnitude and a decrease in the crossover field. Finally, the third peculiarity is related to the remarkable deviation of the total magnetoresistance measured at various temperatures from the Kohler's rule. Presence of strong inhomogeneity and disorder in the Bi_1.9Lu_0.1Te₃ structure concluded from the magnetoresistance peculiarities can be responsible for the remarkable reduction in the total thermal conductivity of this compound.     

Pressure-induced band cross-over in Pb1−x Sn x Te

Resistivity and thermoelectric power studies have been carried out on two semiconductor alloy systems viz Pb_0·8Sn_0·2Te and Pb_0·6Sn_0·4Te up to 35 kbar pressure. Thermoelectric power and resistivity data on Pb_0·8Sn_0·2Te indicate that the energy gapE _g=E _{L −} ⁶ −E _{L 6} ⁺ decreases with pressure resulting in a zero gap state near 35 kbar pressure. TEP studies on the alloy system Pb_0·6Sn_0·4Te provide direct evidence for a pressure induced L ₆ ⁻ →L ₆ ⁺ cross over transition.     

分离富集金、铂、钯的碲共沉淀物研究

利用不同酸溶解Au,Pt,Pd的碲共沉淀产物的方法,推断其化学成分;并用X射线衍射(XRD)对沉淀产物的成分进行进一步分析确认,从中研究碲共沉淀分离富集Au,Pt,Pd的机理。研究结果表明,在碲共沉淀中,Au主要以单质的形式,Pt和Pd以碲化物形式与Te一起沉淀,为微量或痕量贵金属的分离富集过程提供了理论依据。     

The existence region of the Hg0.8Cd0.2Te phase field

The existence region of the Hg0.8Cd_0.2Te phase field has been re-examined using three techniques: Hall measurements, p-n junction depth measurements on material which had been annealed to produce an n-type skin following equilibration at high temperature, and quantitative modelling of experimental observations of gettering of silver in (Hg,Cd)Te. The results we obtain are generally in good agreement with previously reported measurements, although some systematic disagreement is found, particularly under tellurium saturated conditions for temperatures less than 450‡C.     

电化学方法在金属碲化物合成中的应用

介绍了用电化学方法在室温合成金属硫族化合物的最新进展。该方法是在有机溶剂低温合成技术的基础上发展起来的 ,电解液以乙二胺为溶剂 ,以四烷基胺的碘化物和溴化物为支持电解质 ,以二元的金属碲化物为阴极 ,在室温下可制得许多具有独特结构的一维 Au,Ga,In,Sn和 Sb的碲化物。该技术尚在开发研究阶段 ,有待于进一步的发展     

In situ analysis of bismuth telluride electrodeposition using combined spectroscopic ellipsometry and electrochemical quartz crystal microbalance

Electrodeposition of bismuth telluride (Bi₂Te₃) in an acidic medium with Arabic gum by galvanostatic polarization has been investigated. Simultaneous in situ spectroscopic ellipsometry and gravimetric measurements have been performed to study the morphological evolution of the compound. A progressive covering stage was demonstrated and revealed that a 40 nm thick film has already acquired morphological and optical behavior similar to that of thicker films. The optical thickness and electrochemical quartz crystal microbalance (EQCM) mass are coherent with a density of 7.06. Combined gravimetric and coulometric data confirm the formation of Bi₂Te₃ by determining the ratio m/z.     

可见光下发绿光的聚苯乙烯/CdTe复合材料的制备及光学性能研究

首先合成了带正电荷的十二烷基二甲基乙烯基卞基氯化铵,通过静电作用将其与用巯基丙酸修饰的带负电荷的CdTe纳米量子点结合,得到包覆有CdTe量子点的可聚合性的单体,将其与苯乙烯本体共聚后得到可见光下可发绿光的聚苯乙烯（PS）/CdTe复合材料。采用红外光谱、扫描电子显微镜、透射电子显微镜表征其结构,并用紫外-可见光吸收光谱、荧光光谱测试其光学性能。结果表明,在紫外到可见光区域（380~480 nm）激发下,该复合材料均可发出绿光,当包覆有CdTe纳米量子点的可聚合性的单体的含量为1.2 %（质量分数,下同）时,材料的荧光量子效率可达到9.6 %。