n型Bi_2Te_(3-y)Se_y温差电材料薄膜的电化学制备及表征

采用电化学控电位的方法在不锈钢基片上电沉积制备了Bi2Te3-ySey温差电材料薄膜。研究了电沉积溶液中硒含量与薄膜中硒含量的关系,考察了不同沉积电位对电沉积Bi2Te3-ySey薄膜的温差电性能的影响,并采用ESEM、EDS、XRD等方法对电沉积薄膜的形貌、成分及结构进行了分析。结果表明,在含有Bi3 、HTeO2 和Se4 的电沉积溶液中,采用电化学沉积的方法,可实现铋、碲、硒三元共沉积,生成Bi2Te3-ySey半导体化合物。改变电沉积溶液组成,可控制Bi2Te3-ySey化合物中硒的掺杂浓度。-0.04V沉积电位下制备的Bi2Te3-ySey薄膜较平整、致密,组成为Bi2Te2.7Se0.3。退火处理可提高电沉积Bi2Te3-ySey薄膜的塞贝克系数,且控制沉积电位为-0.04V下制备的Bi2Te3-ySey薄膜退火后的塞贝克系数为-123μV·K-1。     

CuInSe_2薄膜的电化学沉积及其形成机理

采用电化学沉积法制备了太阳电池用CuInSe2薄膜.利用循环伏安法(CV)、X射线能谱(EDS)和X射线衍射技术(XRD)研究了电沉积过程中CuInSe2的形成机理,并研究了制备工艺对膜层成分、形貌和物相结构的影响.研究结果表明,铟进入固相是通过In3+受Cu3Se2诱导作用欠电势还原或者In3+与H2Se反应这两种途径实现;先沉积的Cu3Se2与新生成的铟或铟硒化合物反应最后生成CuInSe2.在阴极电位为-0.58~-0.9 V(vs.SCE)时出现了不随电位变化的极限还原电流,在该电位范围内进行电沉积获得了化学计量组成稳定可控且相对致密平整的CuInSe2薄膜.电沉积的CuInSe2薄膜经真空退火处理后结晶质量得到明显改善.     

一步法电化学沉积Cu(In1-x,Gax)Se2薄膜的特性

在CuCl2、InCl3、GaCl3及H2SeO3组成的酸性水溶液电沉积体系中, 对Mo/玻璃衬底上一步法电沉积Cu(In1-x, Gax)Se2(简写为CIGS)薄膜进行了研究. 为了稳定溶液的化学性质, 在溶液中加入邻苯二甲酸氢钾和氨基磺酸作为pH缓冲剂, 将溶液的pH值控制在约2.5, 并提高薄膜中Ga的含量. 通过大量实验优化了溶液组成及电沉积条件, 得到接近化学计量比贫Cu 的CIGS薄膜(当Cu与In+Ga的摩尔比为1时, 称为符合化学计量比的CIGS薄膜; 当其比值为0.8-1时, 称为贫Cu或富In的CIGS 薄膜)预置层, 薄膜表面光亮、致密、无裂纹. 利用循环伏安法初步研究了一步法电沉积CIGS薄膜的反应机理, 在沉积过程中, Se4+离子先还原生成单质Se, 再诱导Cu2+、Ga3+和In3+发生共沉积. 电沉积CIGS薄膜预置层在固态硒源280 ℃蒸发的硒气氛中进行硒化再结晶, 有效改善了薄膜的结晶结构, 且成份基本不发生变化,但是表面会产生大量的裂纹.     

离子液体电沉积CuIn_xGa_(1-x)Se_2薄膜(英文)

采用循环伏安法(CV)对离子液体Reline中三元CuCl2+InCl3+SeCl4体系和四元CuCl2+InCl3+GaCl3+SeCl4体系的电化学行为进行了研究。研究表明,In3+并入三元CIS(Cu-In-Se)薄膜体系和Ga3+并入四元CIGS(Cu-In-Ga-Se)薄膜体系均有两种途径:一是发生共沉积,二是直接还原。利用电感耦合等离子体发射光谱(ICP)和扫描电镜(SEM)对沉积电势、镀液温度和主盐浓度对CIGS薄膜组成、镀层表面形貌的影响进行了测试,结果表明通过工艺参数的选择可以控制Ga/(Ga+In)和CIGS薄膜组成并得到化学计量比为Cu1.00In0.78Ga0.27Se2.13的薄膜。     

亚硒酸钠在L-半胱氨酸自组装类生物膜修饰电极上的电化学行为

利用L-半胱氨酸自组装膜修饰金电极(L-Cys,Au/SAMs), 在0.05mol/L H_2SO_4 底液中研究了 Na_2SeO_3 的电化学特性.在0.00～1.30 V (vs. SCE) 电位范围内对微量Na_2SeO_3进行循环伏安扫描,发现L-Cys, Au/SAMs修饰电极在峰电位0.89 V处有灵敏的Se的氧化溶出峰.通过比较裸金电极和修饰电极在Na_2SeO_3 溶液中的电化学特性发现,修饰电极通过巯基中的S与Na_2SeO_3发生氧化还原作用生成Se,且修饰电极对沉积在电极表面的Se的氧化过程具有催化作用.根据Na_2SeO_3在单分子膜上的电化学行为,提出了单分子膜中硫(Au-S)与Se(Ⅳ)作用生成Se的反应机理、Se电化学催化氧化机理及巯基化合物通过生成纳米硒生物吸收Se的类生物膜模型.     

探究二氧化硫在盐酸中分别与铜单质、二价铜离子、氯化铁溶液的反应*

通过实验发现:SO₂在盐酸中既能将Cu单质氧化为+1价铜的化合物,也能把Cu²⁺还原为+1价铜的化合物,且发现SO₂将Cu单质氧化或将Cu²⁺还原都需要有Cl^-来参与反应,其反应机理需要通过SO₂和FeCl₃的反应(I^-催化)来进一步探究。这几个探究实验皆易于操作与观察,具有显著的实验表征,有利于从宏观辨识深入到微观探析的过程。     

p型Se的电沉积及其转化为n型CdSe的机理研究

利用线性电位扫描光伏安法等技术研究钛基体上Se半导体薄膜的电化学形成及转化过程.实验结果表明,在H_2SeO_3溶液中进行电沉积可获得p型Se薄膜,它可在酸性CdSO_4溶液中阴极转化为n型CdSe.讨论了Se的电沉积动力学及其转化为CdSe的可能机理.所述原理可望用于p-n异质结的电化学制备.     

n型Bi2Te3-ySey温差电材料薄膜的电化学制备及表征

采用电化学控电位的方法在不锈钢基片上电沉积制备了Bi₂Te_3-ySe_y温差电材料薄膜。研究了电沉积溶液中硒含量与薄膜中硒含量的关系，考察了不同沉积电位对电沉积Bi₂Te_3-ySe_y薄膜的温差电性能的影响，并采用ESEM、EDS、XRD等方法对电沉积薄膜的形貌、成分及结构进行了分析。结果表明，在含有Bi³⁺、HTeO₂⁺和Se⁴⁺的电沉积溶液中，采用电化学沉积的方法，可实现铋、碲、硒三元共沉积，生成Bi₂Te_3-ySe_y半导体化合物。改变电沉积溶液组成，可控制Bi₂Te_3-ySe_y化合物中硒的掺杂浓度。-0.04 V沉积电位下制备的Bi₂Te_3-ySe_y薄膜较平整、致密，组成为Bi₂Te_2.7Se_0.3。退火处理可提高电沉积Bi₂Te_3-ySe_y薄膜的塞贝克系数，且控制沉积电位为-0.04 V下制备的Bi₂Te_3-ySe_y薄膜退火后的塞贝克系数为-123 μV·K^-1。     

添加La的Bi2Te3和Bi0.5Sb1.5Te3热电材料的电磁感应熔炼法制备及其热电性能

在N2气保护下,采用电磁感应法制备了添加La的Bi2Te3和Bi0.5Sb1.5Te3。运用X射线粉末衍射、电感耦合等离子光谱和扫描电子显微镜对材料的物相成分和形貌进行了表征。研究了La对Bi2Te3和Bi0.5Sb1.5Te3热电材料的电导率(σ)、Seebeck系数(S)和热导率(κ)的影响。实验结果表明,添加La明显降低了2种材料的热导率,提高了热电优值(ZT),添加La的Bi0.5Sb1.5Te3的热电优值在室温超过了1。     

CH3CH2,CH3CHCl,CH3CCl2与NO2反应微观动力学理论研究

运用量子化学密度泛函理论UB3LYP/6-311+G*和高级电子相关校正的偶合簇(CCSD(T)/6-311+G*)方法,对CH3CH2,CH3CHCl和CH3CCl2自由基与NO2反应的机理和动力学进行了理论研究,得到了体系的势能面信息和可能的反应机理.根据计算得到的各反应热力学参数及反应能垒,采用传统过渡态理论计算了各反应在温度T=298 K和T=700 K时的速率常数.研究结果表明,该类反应均通过1个中间体和1个过渡态生成产物,产物分别为CH3CHO+HNO,CH3CHO+ClNO和CH3CClO+ClNO.     

Growth of ultrathin films of cadmium telluride and tellurium as studied by electrochemical atomic force microscopy

Time dependent, cathodic electrodeposition of ultrathin CdTe and Te films has been studied in 50 mM H(2)SO(4) + 1 mM CdSO(4) + 0.1 mM TeO(2) solutions at room temperature under potential control using electrochemical atomic force microscopy (EC-AFM). The films were also characterized electrochemically and with X-ray diffraction. The growth mechanism and the composition of the films depends on the applied potentials. Island-like growth mode was observed for CdTe films when the deposition potential was -0.35 V (SHE). At a more positive deposition potential of 0.138 V (SHE), Cd was not co-deposited into the film but affected the dynamic growth mode of the deposit. At this voltage smooth Te films were obtained. Depending on the applied potential, Cd acts either as a co-deposition element for CdTe film growth, or as a mediator for layer-by-layer growth of Te films.     

Bismuth telluride (Bi2Te3) nanowires: synthesis by cyclic electrodeposition/stripping, thinning by electrooxidation, and electrical power generation

Nanowires composed of the thermoelectric material Bi2Te3 were synthesized on highly oriented pyrolytic graphite (HOPG) electrodes using the electrochemical step edge decoration (ESED) method. Nanowire synthesis was initiated by applying a voltage pulse of -0.75 V versus SCE for 5 ms to an HOPG electrode in an aqueous solution containing both Bi3+ and TeO22-, thereby producing nuclei at the step edges. Bi2Te3 was electrodeposited onto these nuclei using a cyclic electrodeposition-stripping scheme that involved the electrodeposition of bismuth-rich Bi2Te3 on a negative-going voltammetric scan (to -0.05 V) and the subsequent anodic stripping of excess bismuth from these nanowires during a positive-going scan (to +0.35 V). When this cycle was repeated 10-50 times, Bi2Te3 nanowires in the 100-300-nm-diameter range were obtained. These nanowires were narrowly dispersed in diameter (RSDdia = 10-20%), were more than 100 microm in length, and were organized into parallel arrays containing hundreds of wires. Smaller nanowires, with diameters down to 30 nm, were obtained by electrooxidizing 150-nm-diameter Bi2Te3 nanowires at +0.37 V under conditions of kinetic control. This oxidation process unexpectedly improved the uniformity of Bi2Te3 nanowires, and X-ray photoelectron spectroscopy (XPS) shows that these nanowires retain a Bi2Te3 core but also have a thin surface layer composed of Bi and Te oxides. The ability of Bi2Te3 nanowires to generate electrical power was assessed by transferring ensembles of these nanowires onto cyanoacrylate-coated glass surfaces and evaporating 4-point nickel contacts. A dimensionless figure of merit, ZT, ranging from 0 to 0.85 was measured for fresh samples that were less than 1 day old. XPS reveals that Bi2Te3 nanowires are oxidized within a week to Bi2O3 and TeO2. These oxides may interfere with the application by evaporation of electrical contacts to these nanowires.     

Electrochemical aspects and structure characterization of VA-VIA compound semiconductor Bi2Te3/Sb2Te3 superlattice thin films via electrochemical atomic layer epitaxy

This paper concerns the electrochemical atom-by-atom growth of VA-VIA compound semiconductor thin film superlattice structures using electrochemical atomic layer epitaxy. The combination of the Bi2Te3 and Sb2Te3 programs and Bi2Te3/Sb2Te3 thin film superlattice with 18 periods, where each period involved 21 cycles of Bi2Te3 followed by 21 cycles of Sb2Te3, is reported here. According to the angular distance between the satellite and the Bragg peak, a period of 23 nm for the superlattice was indicated from the X-ray diffraction (XRD) spectrum. An overall composition of Bi 0.25Sb0.16Te0.58, suggesting the 2:3 stoichiometric ratio of total content of Bi and Sb to Te, as expected for the format of the Bi2Te3/Sb2Te3 compound, was further verified by energy dispersive X-ray quantitative analysis. Both field-emission scanning electron microscopy and XRD data indicated the deposit grows by a complex mechanism involving some 3D nucleation and growth in parallel with underpotential deposition. The optical band gap of the deposited superlattice film was determined as 0.15 eV by Fourier transform infrared spectroscopy and depicts an allowed direct type of transition. Raman spectrum observation with annealed and unannealed superlattice sample showed that the LIF mode has presented, suggesting a perfect AB/CB bonding in the superlattice interface.     

Synthesis and characterization of nanostructured bismuth selenide thin films

Nanostructured bismuth selenide thin films have been successfully fabricated on a silicon substrate at low temperature by rational design of the precursor solution. Bi(2)Se(3) thin films were constructed of coalesced lamella in the thickness of 50-80 nm. The nucleation and growth process of Bi(2)Se(3) thin films, as well as the influence of solution chemistry on the film structure were investigated in detail. As one of the most promising thermoelectric materials, the thermoelectric properties of the prepared Bi(2)Se(3) thin films were also investigated. The power factor increased with increasing carrier mobility, coming from the enlarged crystallites and enhanced coalesced structure, and reached 1 μW cm(-1) K(-1).     

Preparation of bismuth telluride thin film by electrochemical atomic layer epitaxy (ECALE)

Thin-layer electrochemical studies of the underpotential deposition (UPD) of Bi and Te on cold rolled silver substrate have been performed. The voltammetric analysis of underpotential shift demonstrates that the initial Te UPD on Bi-covered Ag and Bi UPD on Te-covered Ag fitted UPD dynamics mechanism. A thin film of bismuth telluride was formed by alternately depositing Te and Bi via an automated flow deposition system. X-ray diffraction indicated the deposits of Bi₂Te₃. Energy Dispersive X-ray Detector quantitative analysis gave a 2: 3 stoichiometric ratio of Bi to Te, which was consistent with X-ray Diffraction results. Electron probe microanalysis of the deposits showed a network structure that results from the surface defects of the cold rolled Ag substrate and the lattice mismatch between substrate and deposit. Translated from Chinese Journal of Applied Chemistry, 2005, 22 (11) (in Chinese)     

Influence of electrodeposition conditions on the properties of CdTe films

The results of the influence of electrodeposition conditions on the structural, compositional, optical, and photoelectrochemical properties of CdTe thin films deposited in one-step electrochemical method are presented. The CdTe films were prepared electrochemically from aqueous acidic solution with low ratios of Cd²⁺ ions to Te(IV) ions concentration. Instead of commonly used TeO₂, water-soluble Na₂TeO₃ was used as a source of tellurium ions. The cathodic deposition of CdTe was performed at different constant potentials from solutions containing different cadmium and tellurium ions concentration. As-deposited CdTe thin films were studied by different analytical techniques. The X-ray photoelectron spectroscopy spectra exhibited CdTe formation on the electrode with some amount of tellurium oxides and cadmium oxides. The best quality CdTe deposits, free of TeO₂, were formed in bath containing excess of Cd²⁺ ions and at the potential of ?0.65 V vs. saturated calomel electrode, slightly more positive than E _eq of Cd/Cd²⁺ system. Structural X-ray diffraction studies revealed polycrystallinity of deposits with the highest content of the (111)-oriented cubic (111) form. Optical band gap energy values were found in the range from 1.36 to 1.6 eV for CdTe films prepared at various synthesis conditions. The preliminary photoelectrochemical studies have shown that the variation of the deposition potential as well as bath composition leads to the formation of p- or n-type CdTe films. As-deposited CdTe films were not stable in polysulfide solution under illumination.     

电活性铁氰化镍膜电极对稀土钇的电控离子分离

通过电沉积方法分别在镀铂石英晶片和铂基底上制备了电活性铁氰化镍膜,并考察了膜电极在含钇离子溶液中的电控离子交换性能. 在0.1 mol·L^-1的硝酸钇溶液中,使用循环伏安法及石英晶体微天平技术测试考察了铁氰化镍膜对钇离子的置入释放性能及对应的质量变化,同时比较了铁氰化镍膜电极在Y(NO₃)₃和Sr(NO₃)₂溶液中的电化学性能. 在0.1 mol·L^-1 [Y(NO₃)₃ + Sr(NO₃)₂]混合溶液中,通过循环伏安法分析了薄膜对Y³⁺/Sr²⁺离子的选择性. 用扫描电子显微镜观察了铁氰化镍膜的表面形貌,并通过X射线光电子能谱仪测定了膜在氧化和还原状态下的元素组成. 结果表明,铁氰化镍膜在含Y³⁺溶液中具有良好的离子交换行为,其中氧化过程薄膜质量减少,对应着钇离子的释放;还原过程薄膜质量增加,对应钇离子的置入;在0.0 V或0.9 V调控膜电极的氧化还原状态实现对钇离子的有效分离.     

Structure and thermoelectric properties of the new quaternary bismuth selenides A(1-x)M(4-x)Bi(11+x)Se21 (A = K and Rb and Cs; M = Sn and Pb)--members of the grand homologous series Km(M6Se8)m(M(5+n)Se(9+n))

Several members of the new family A(1-x)M(4-x)Bi(11+x)Se21 (A = K, Rb, Cs; M = Sn, Pb) were prepared by direct combination of A2Se, Bi2Se3, Sn (or Pb), and Se at 800 degrees C. The single-crystal structures of K(0.54)Sn(3.54)Bi(11.46)Se21, K(1.46)Pb(3.08)Bi(11.46)Se21, Rb(0.69)Pb(3.69)Bi(11.31)Se21, and Cs(0.65)Pb(3.65)Bi(11.35)Se21 were determined. The compounds A(1-x)M(4-x)Bi(11+x) Se21 crystallize in a new structure type with the monoclinic space group C2/m, in which building units of the Bi2Te3 and NaCl structure type join to give rise to a novel kind of three-dimensional anionic framework with alkali-ion-filled tunnels. The building units are assembled from distorted, edge-sharing (Bi,Sn)Se6 octahedra. Bi and Sn/Pb atoms are disordered over the metal sites of the chalcogenide network, while the alkali site is not fully occupied. A grand homologous series Km(M6Se8)m(M(5+n)Se(9+n)) has been identified of which the compounds A(1-x)M(4-x)Bi(11+x)Se21 are members. We discuss here the crystal structure, charge-transport properties, and very low thermal conductivity of A(1-x)M(4-x)Bi(11+x)Se21.     

碲铋渣中铋的测定

讨论了在pH=9.4～10.0的氨性溶液中,利用Fe3+与Te4+、Bi3+生成三元共沉淀物,分离其它杂质,然后用KOH溶解Te,从而达到Te,Bi分离的目的。在pH=1.5～1.7的溶液中,利用抗坏血酸掩蔽铁,以硫脲-PAR作为指示剂,用EDTA标准溶液滴定Bi。当n=6时,相对标准偏差为0.4%,回收率为98.53%～102.2%,方法准确、可靠。