Thermodynamic properties of arsenic sulfides studied by EMF measurements

The solid-state phase equilibria and thermodynamic properties of alloys in the As-S system have been studied using emf measurements. The temperature and composition dependences of the emf confirm the existence of As₂S₅, As₂S₃, AsS, and As₄S₃ with narrow homogeneity ranges. The emf data are used to calculate relative partial molar functions of the As in the alloys and the standard Gibbs energies and standard entropies of the arsenic sulfides.     

Thermodynamic study of the Ag2S-As2S3-S system by EMF measurements with Ag4RbI5 as a solid electrolyte

The Ag-As-S system has been studied in the composition region Ag₂S-As₂S₃-S at temperatures from 300 to 380 K using emf measurements with Ag₄RbI₅ as a Ag⁺ ion conducting solid electrolyte, and its subsolidus phase diagram has been mapped out, including the ternary compounds AgAsS₂, Ag₃AsS₃, and Ag₇AsS₆. From the emf data, we have calculated the partial molar thermodynamic functions $\left( {\left( {\Delta \bar G,\Delta \bar H,\Delta \bar S} \right)} \right)$ of the silver in the three-phase regions AgAsS₂ + As₂S₅ + As₂S₃, Ag₃AsS₃ + AgAsS₂ + S, and Ag₇AsS₆ + Ag₃AsS₃ + S, which were then used to evaluate the standard thermodynamic functions of formation and standard entropies of the ternary compounds by the method of potential-determining reactions.     

Phase diagram and thermoelectric properties of Ag3−x Sb1+x Te4 system

In order to obtain better thermoelectric performance in the composition domain should be stabilized, the phase diagram of the Ag_3–x Sb_1+x Te₄ system by varying the Ag:Sb ratio. The phase diagram is investigated using the differential thermal analysis and the powder X-ray diffraction techniques. The Seebeck coefficient and the electrical resistivity of the grown bulk crystals of the system are also measured. The phase diagram of the Ag_3–x Sb_1+x Te₄ system indicates that a mixed phase of AgSbTe₂ and Ag₂Te, which is expected to show higher thermoelectric performance, exists in a wide temperature range between 600 and 830 K at a composition of Ag_2.2Sb_1.8Te₄. The maximum of Seebeck coefficient for AgSbTe₂ (x = 1) is 0.73 mV/K at about 680 K. The thermoelectric performance is lowered by the compositional deviation from Ag:Sb:Te = 1:1:2.     

Thermoelectric properties of Zn4Sb3 processed by sinter-forging

Sinter-forging technique was applied to produce high efficiency ε-Zn₄Sb₃ bulk specimens. Near single phase Zn₄Sb₃ with a remnant ZnSb was obtained using nominal stoichiometric powder mixtures. Thermoelectric properties in sinter-forged specimens as a function of temperature were investigated up to 600 K and compared with results of other studies. Transport properties at room temperature were also evaluated. Thermoelectric properties of Zn₄Sb₃ processed by sinter-forging are comparable to the published data. Sinter-forging offers a potential processing route to produce a bulk Zn₄Sb_3.     

Fast preparation and thermoelectric properties of Zn4Sb3 by HPHT

In this paper, crack-free bulk thermoelectric material Zn₄Sb₃ was prepared rapidly by high pressure and high temperature (HPHT) method. Near a single-phase Zn₄Sb₃ specimen was obtained using nominal stoichiometric powder mixtures, which were indexed by powder X-ray diffraction. The temperature-dependent thermoelectric properties including the Seebeck coefficient and electrical resistivity were studied. The maximum power factor of Zn₄Sb₃ specimen prepared by HPHT reaches 10.8 ??W/(cmK²) at 637 K, which is comparable to the published data. The results show that the HPHT offers potential processing route to produce the thermoelectric material Zn₄Sb₃ quickly and effectively.     

Optical properties of Ag8In14Sb55Te23 phase-change films

Ag₈In₁₄Sb₅₅Te₂₃ phase-change films were deposited on K9 glass substrates by RF magnetron sputtering technology using an Ag–In–Sb–Te alloy target. The optical properties and short-wavelength optical storage properties of Ag₈In₁₄Sb₅₅Te₂₃ films were studied. X-Ray diffraction results indicate that the crystallized compounds consist mainly of AgSbTe₂, with small amounts of Sb and AgInTe₂. Comparatively large absorbance was observed in the wavelength range of visible light. The optical storage characteristics of Ag₈In₁₄Sb₅₅Te₂₃ thin films indicate that larger reflectivity contrast can be obtained at lower writing power and shorter writing pulse width.     

Electronic structure and photoelectrical properties of Ag2In2SiSe6 and Ag2In2GeSe6

High-quality Ag₂In₂SiSe₆ and Ag₂In₂GeSe₆ single crystals have been successfully grown by the vertical Bridgman–Stockbarger method and the horizontal gradient freeze technique, respectively. For pristine and Ar⁺ ion-irradiated surfaces of the single crystals under study, X-ray photoelectron core-level and valence-band spectra have been measured. Results of these studies allow for concluding that the Ag₂In₂SiSe₆ and Ag₂In₂GeSe₆ single crystal surfaces are sensitive with respect to Ar⁺ ion-irradiation. In particular, Ar⁺ ion-bombardment with energy of 3.0 keV during 5 min at an ion current density of 14 μA/cm² has induced some modification in top surface layers leading to an increase of content of In atoms in the layers. Comparison on a common energy scale of the X-ray emission Se Kβ₂ bands representing energy distribution of the Se 4p states and the X-ray photoelectron valence-band spectra reveal that the main contribution of the valence Se p states occur in the upper portion of the valence band, with also their significant contributions in other valence band regions of the Ag₂In₂SiSe₆ and Ag₂In₂GeSe₆ single crystals. In addition, for the single crystals under consideration, temperature dependences of specific dark conductivity and spectral distributions of photoconductivity have been explored. It has been established that the Ag₂In₂SiSe₆ and Ag₂In₂GeSe₆ single crystals are high-resistance semiconductors with value of the specific electrical conductivity σ ≈ 1.67 × 10^–9 Ω^–1 сm^–1 (at Т = 300 K). The both compounds are materials with p-type conductivity.     

含银铅锑多元合金真空蒸馏富集银锑的研究

采用含银铅锑多元合金为原料,对其真空蒸馏法富集Ag、Sb的可行性和工艺进行探讨,考察蒸馏温度、恒温时间对合金中各组分的挥发行为影响,理论和实验均证实了该方法可行。试验结果表明:系统压力5~25 Pa,Ag,Sb的挥发随着温度的增加和恒温时间的延长而加剧,蒸馏温度为1223 K,恒温时间30~120 min时,Ag的富集率均大于99.28%,Sb的挥发率为89.7%~92.8%;X射线衍射仪研究表明残留物中形成化合物Ag3Sb,Cu2Sb,Cu10Sb3,导致Sb不能彻底挥发;蒸馏过程中,系统压力随着恒温时间的延长而下降,且蒸馏温度越高下降越明显。     

Mechanical alloying and thermoelectric properties of Zn4Sb3

Thermoelectric Zn₄Sb₃ bulk specimens were produced by mechanical alloying of elemental powders and consolidated by hot pressing. Single phase Zn₄Sb₃ was not obtained using a nominal stoichiometric composition, but near single phase Zn₄Sb₃ with remnant elemental Zn having a relatively high density was produced using a nominally 11.7 at.% Zn rich powders. Phase transformations during mechanical alloying were systematically investigated using XRD and SEM. Thermoelectric and transport properties were evaluated for the hot pressed specimens and compared with results of analogous studies.     

Thermoelectric properties of Sb2Te3 thin films by electron beam evaporation

This study applies the thermoelectric grains of Sb2Te3 on conductive glass to evaporate Sb2Te3 thin films by the electron beam evaporation method. Through experimental tests with different evaporation process parameters and film annealing conditions, thin films with better Seebeck coefficient, resistivity (p) and power fact (PF) can be obtained. Experimental results show that when thin films are annealed, their defects can be decreased accordingly, and carrier mobility can be enhanced to further elevate the conductivity of thin films. When the substrate temperature is set at 200 degrees C to fabricate Sb2Te3 thin films by the evaporation process and by annealing at 220 degrees C for 60 minutes, the Seebeck coefficient of Sb2Te3 thin films increase from 87.6 microV/K to 177.7 microV/K; resistivity falls from 6.21 m ohms-cm to 2.53 m ohms-cm and PF can achieve the maximum value of 1.24 10(-3) W/K2 m. Finally, this study attempts to add indium (In) to Sb2Te3 thin films. Indium has been successfully fabricated In3SbTe, thin films. This study also analyzes the effects of In on the thermoelectric properties of In3SbTe2 thin films.     

Optical properties of Sb2Se3 thin films

The optical constants (the refractive index n and the absorption index k) of Sb₂Se₃ thin films deposited at room temperature on quartz have been calculated in the wavelength range (5000–2000 nm) using a transmission spectrum. Both n and k were found to be practically independent on either time, up to 6 months, or the film thickness in the range of 102–760 nm. Beyond the absorption edge, the absorption is due to allowed indirect and direct transitions with energy gaps of 1.225 and 1.91 eV, respectively. The value of the optical gap depends on the annealing temperature. X-ray analysis showed that the prepared films at room temperature had amorphous structure while the films annealed at 200°C for 1 h were verified to be crystalline.     

Effect of Sb5+ substitution on the dielectric properties of Ag(Nb0.8Ta0.2)O3 ceramics

Sb₂O₅ were selected to substitute (Nb_0.8Ta_0.2)₂O₅ and the effects of substitution on the dielectric properties of Ag(Nb_0.8Ta_0.2)O₃ ceramics were studied. The dielectric properties of Ag(Nb_0.8Ta_0.2)_1−xSb_xO₃ ceramics were found to be improved by the substitution of Sb for Nb/Ta. The ε value of Ag(Nb_0.8Ta_0.2)_1−xSb_xO₃ ceramics sintered at 1060 °C increased from 430 to 825 with x increasing from 0 to 0.08, the tanδ value decreased sharply from 0.0085 to 0.0023 (at 1 MHz) with x increasing from 0 to 0.04, and then kept to a lower tanδ value ∼ 0.0024 with x to 0.08. The TCC values decreased from + 1450 ppm/°C for x = 0 to − 38.5 ppm/°C for x = 0.08. The Ag(Nb_0.8Ta_0.2)_1−xSb_xO₃ ceramics with x = 0.08 sintered at 1050 °C exhibited the optimum dielectric properties of ε ∼ 854, tanδ ∼ 0.0024 (1 MHz), and TCC ∼ 36.86 ppm/°C.     

Ga掺杂Zn4Sb3体系热电性能的研究

首先在5-310K温度范围内，研究了Ga替代对化合物（Zn1-xGax）4Sb3的低温热电性能的影响。研究发现相对于无掺杂的Zn4Sb3，（Zn1-xGAx）4Sb3（x≠0）的低温热导率明显减小，而且随着Ga替代量的增加而不断减小。另外，轻掺杂条件下（X≤0．15），掺杂后的电阻率和热电势都减小．而随后对β-Zn4Sb3和β-（Zn0.85Ga0.15）4Sb3的高温（300-670K）热电性能进行了测量，结果充分表明合适量的Ga替代Zn（比如x=0．15），可以优化β-Zn4Sb3的高温热电性能。     

Electrical properties of polycrystalline Sb2Te3 films

Single-phase polycrystalline stoichiometric films of Sb₂Te₃ with different thicknesses were prepared on glass substrates by a flash evaporation technique at constant substrate temperature of 423 K. The electrical properties of these films, such as resistivity, Hall mobility, carrier concentration and activation energy, were determined for different film thicknesses. The optical absorption of these films was also studied. The implications are discussed.     

First-principles calculations of mechanical and thermodynamic properties of YAlO3

First-principles calculations are performed to investigate the crystal structure, electronic properties, the elastic properties, hardness and thermodynamic properties of YAlO₃. The calculated ground-state quantities such as lattice parameter, bulk modulus and its pressure derivative, the band structure and densities of states were in favorable agreement with previous works and the existing experimental data. The elastic constants C_ij, the aggregate elastic moduli (B, G, E), the Poisson’s ratio, and the elastic anisotropy have been investigated. YAlO₃ exhibits a slight elastic anisotropy according to the universal elastic anisotropy index A^U = 0.24. The estimated hardness for YAlO₃ is consistent with the experimental value, and Al–O bond in AlO₆ octahedra plays an important role in the high hardness. The Y–O bonds in YO₁₂ polyhedra exhibit different characteristic. Using the quasi-harmonic Debye model considering the phonon effects, the temperature and pressure dependencies of bulk modulus, heat capacity and thermal expansion coefficient are investigated systematically in the ranges of 0–20 GPa and 0–1300 K.     

ZnO:Sb3+纳米粉的制备及发光性能的研究

采用共沉淀法制备了六方纤锌矿结构的Sb3+掺杂ZnO纳米荧光粉,并系统研究了不同Sb3+掺杂浓度、不同煅烧温度和时间对其发光性能的影响.借助于XRD、SEM、荧光光度计等测试手段对粉体的相组成、形貌及其光致发光性能进行了表征.结果表明:掺杂Sb3+样品的粒度小于未掺杂样品的粒度,当Sb3+掺杂浓度小于3％时,ZnO:S...     

Superconducting Properties of Ag and Sb Substitution on Low-Density YBa2Cu3O δ Superconductor

The effects of silver (Ag) and antimony (Sb) substitution on low-density YBa₂Cu₃O _δ (YBCO) superconductor were investigated. Two series of sample with a nominal composition of YBa_2?x Ag _x Cu₃O _δ and YBa_2?x Sb _x Cu₃O _δ where x=0.05, 0.10, 0.15, 0.20, 0.30, 0.40 and 0.50 were synthesized and characterized. All Ag-doped samples showed metallic behavior at the normal state and T _C?onset was found at 90 K. T _C?zero decreased as the Ag concentration increased. Optimum Ag concentration was achieved at x=0.20 where T _C?zero has the highest value of 87 K and J _C at 70 K is 16.50 A/cm². For Sb-doped case with x≤0.30, the samples showed metallic behavior above T _C?onset while semiconducting behavior was shown for x≥0.40. The optimum Sb concentration was achieved at x=0.15 where T _C?zero is 85 K and J _C value measured at 70 K is 2.75 A/cm². T _C?onset and T _C?zero were found to decrease toward higher Sb concentration. The crystallographic structure transformed to tetragonal in Sb-doped samples of x≥0.30 while other samples remain orthorhombic.     

Electrical and optical properties of (Sb2Se3)2 (Sb2Te3)1 thin films

A study of the synthesized (Sb₂Se₃)₂ (Sb₂Te₃)₁ glassy system has been carried out, X-ray diffraction (XRD) patterns and differential thermal analysis (DTA) of the system studied were used to obtain an insight into the structural information. An investigation of the electrical and optical properties of (Sb₂Se₃)₂ (Sb₂Te₃)₁ thin films prepared by thermal evaporation having different thicknesses (89.2, 214, 223 nm) and annealing temperatures ranging from 300 to 473 K has been carried out. The effect of the thickness and heat treatment on the activation energy E for d.c. conductivity and the density of localized states at the Fermi level N(E_F) were carried out. The electrical conductivity measurements depend on the thickness and annealing temperature, and exhibit two types of conduction mechanisms. Optical absorption measurements have been made on as-deposited and annealed films for the investigated system. The optical transition was found to be indirect. The optical energy gap (E_opt) decreases with increasing thickness and annealing temperatures (below T_g). The corresponding band is approximately twice the conduction activation energy. This effect is interpreted in terms of the density of states model proposed by Mott and Davis. © 2002 Kluwer Academic Publisher     

中国直流电动势副基准的现状

中国计量科学研究院（ＮＩＭ）的直流电动势副基准经多次与国内外约瑟夫森电压标准比对表明，七年中最大累积变化约为０．２１×１０－６，平均每年变化仅０．０３ｕＶ．从１９９５年１月１日起改值０．２０×１０－６后，可与国际电压值在３×１０－８误差范围内保持一致．