Relationship between the short-range order and electrical resistivity in liquid indium-antimony

The composition dependencies of local structure and electronic structure, as well as the electric resistivity of liquid indium-antimony alloys have been investigated by the first-principles molecular dynamics simulations. It is shown that the variations of InIn, InSb and SbSb coordination tendency and the projected density of states of In and Sb in liquid In_xSb_1 ? x depend on the Sb concentration, and electric resistivity of liquid indium-antimony also reveals a regular change trends as a function of Sb concentration. Further analysis confirmed that there are explicit relationships between the short range structural parameters and electrical resistivities in liquid In_xSb_1 ? x.     

Local atomic and electronic structures of equiatomic liquid alloy KSb from 923 to 1773 K

The local atomic and electronic structures of equiatomic liquid alloy KSb have been investigated using ab initio molecular dynamics simulations. There is a small peak located at about 62° in the covalent SbSb bond-angle distribution function. The height of 62° peak increases with temperature. The further analysis show that this peak attributes to the triangular structures with each Sb atom covalently bonded to the other two in the liquid KSb and their number increases with temperature. Therefore, there exist isolated Sb atoms, covalently bonded Sb dimers, triangles with three covalent SbSb bonds and short covalently bonded Sb chains in the liquid KSb. Upon temperature increasing the covalent Sb chains tend to break into short pieces so that the isolated Sb atoms, covalently bonded Sb dimers and triangles with three covalent SbSb bonds increase in numbers. The obtained total electronic densities of states at different temperatures give a reasonable explanation of the electronic conductivity increasing with temperature.     

Local structure of liquids Al2O3 and GeO2 under densification

Molecular dynamic simulation has been conducted to study the local structure of liquid Al₂O₃ and GeO₂ under densification. Those liquids are found to be a mixture of species of TO_x. Here T is Ge or Al and x = 4, 5 and 6. This result is supported by the fact that the density, fraction of oxygen connectivity and volume of different void kinds are a linear function of TO_x fraction. The microscopic mechanism of liquid densification is quantified and interpreted in term of the change in TO_x fraction.     

X-ray diffraction measurements for expanded fluid mercury up to the supercritical region

The energy-dispersive X-ray diffraction measurements for expanded fluid Hg have been carried out in the density region from 13.55 to 6.8 g cm⁻³ including the metal-non-metal transition region. It was found that the volume expansion of liquid Hg in the metallic region is not accompanied by a uniform increase of interatomic distance, r₁, but mainly caused by a decrease of coordination number, N₁. When the transition region is approached, the rate of decrease of N₁ becomes small and r₁ starts to elongate.     

The influence of the intensity of melt stirring on the radial impurity distribution in proustite single crystals grown by the Stockbarger method using ACRT

The influence of the intensity of melt stirring on the radial impurity distribution and optical quality of proustite single crystals grown by the Stockbarger method using ACRT is studied by the example of Cu, Sb and Mg impurities. We report results obtained in a wide range of Taylor numbers (1.9×10⁵<Ta<7.12×10⁷). The studies revealed that the ACRT can be applied validly to decrease the impurity content during the growing of high-quality single crystals.     

X-ray diffraction measurements for liquid As2Se3 up to the semiconductor-metal transition region

X-ray diffraction measurements were performed for liquid (1-) As₂Se₃ at temperatures and pressures up to 1500°C and 70 bar. A high-pressure vessel and a sapphire sample cell were developed, according to the authors' own design, for measurements using the energy-dispersive method. The structure factor becomes broadened with increasing temperature and changes significantly at about 1000°C accompanied by the semiconductor-to-metal (SC-M) transition; the first sharp diffraction peak around 1.2Å⁻¹ disappears and the second and third maxima merge. The nearest-neighbor distance and the average coordination number start to increase when the SC-M transition occurs. The density of 1-As₂Se₃ in the temperature and pressure range up to 1600°C and 700 bar, respectively, were also measured by the X-ray absorption method. A volume contraction occurs in the SC-M transition region.     

The structure of liquid Sb---Se alloys

The structure of liquid Sb_1-xSe_x alloys with x = 0.5, 0.6 and 0.7 was investigated in the temperature range of 600–800°C. The neutron diffraction measurements were carried out by using the high intensity total (HIT) scattering spectrometer of the booster synchrotron utilization facility (BSF) at the National Laboratory for High Energy Physics. A prepeak is observed in the structure factor for these three alloys. It suggests that the medium-range order stillo remains melting for liquid Sb_1-xSe_x alloys, with x = 0.5, 0.6 and 0.7. The structure factor liquid Sb₂Se₃ alloys shows no appreciable temperature variation. For liquid Sb_0.5Se_0.5 alloy, the intensity of the prepeak exhibits an apparent decrease in the temperature range in which the non-metal-metal transition occurs. The non-metal-metal transition in liquid Sb---Se alloys is due to the change in the medium range structure.     

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。     

基于第一性原理的掺杂单层WS2的光电效应

基于非平衡态格林函数-密度泛函理论,采用第一性原理方法,计算了VA族元素(N、P、As或 Sb) 掺杂单层WS₂的光电效应,并解释了掺杂提高光电效应的微观机理。结果表明:在线性极化光照射下,单层WS₂中可以产生光电流。由于掺杂降低了单层WS₂的空间反演对称性,导致N、P、As或 Sb分别掺杂的单层WS₂的光照中心区产生的光电流明显提升。其中N掺杂的效果最好,掺杂后的单层WS₂在光子能量3.1 eV时获得最大光电流(1.75),并且偏振灵敏度达到最大(18.1),P、As、Sb分别掺杂的单层WS₂在光子能量3.9 eV时取得较大的光电流,并且有较高的偏振灵敏度。研究结果表明通过掺杂能够有效增强光电效应,获得更高的偏振灵敏度,揭示了掺杂单层WS₂在光电子器件领域潜在的应用前景。     

Phase Equilibrium of the Ga–Al–Sb system

Employing the method of liquid-phase epitaxy (LPE) solid-solutions of Ga_1–xAl_xAl_xSb (0 ≦ x ≦ 0.8) have been obtained. The dependence of Sb solubility on Al concentration in the liquid phase at 403°C, 452°C, 500°C has been established. The dependence of AlSb concentration in the solid phase on the composition of the liquid phase has been investigated at 452°C. Using the chemical constants equilibrium method, the phase equilibrium of the Ga–Al–Sb system in the region of liquid phase composition near the Ga-rich corner of the phase diagram has been calculated. The comparison of experimental and calculated data for the liquid and solid phases shows their agreement within the limits of experimental error.     

LPE Growth of Ga1 – xInxSb Multi-grading Layers

Electronegativity difference approach (ENDA) has been successfully employed to obtain good prediction of the In atomic fraction, energy bandgap and lattice constant of the Ga_{1 – x}In_xSb/Ga_{1 – y}In_ySb/GaSb system. Nearly lattice-matched GalnSb epilayers with In atomic fraction of 0.42 have been obtained by the liquid phase epitaxy. The cut-off wavelength was 2.2 μm at room temperature.     

Single-crystal growth of sulphospinel CuIr2S4 from Bi solution

Single crystals of a sulphospinel CuIr₂S₄ have been grown from bismuth solution by a slow cooling method for the first time. The grown crystals have a maximum edge of about 1 mm in size and a mirror-like shining surface. Optimum growth conditions are fairly strict. The specific weight of starting materials for the crystal growth is found to be 0.30 g of CuIr₂S₄ and 10.0 g of Bi in order to obtain good quality crystals. The starting and finishing temperatures for the slow cooling step in the temperature control are 1000 and 500°C. The pertinent cooling rate is 2°C/h. Since the volume of bismuth itself expands in the transition from liquid phase to solid phase, a simple method of separation of the grown crystals from the liquid solution will be proposed for avoiding the mechanical damages to the grown crystals. The single crystals have the normal-spinel structure of the lattice constant a=9.849 Å at room temperature. A step-like anomaly in the susceptibility of the single crystals, corresponding to the metal–insulator transition in the resistivity, occurs much sharply than in the powder specimen.     

The growth kinetics of (SmY)3(FeGa)5O12 epitaxial layers in the 920–980°C range

The growth kinetics of (SmY)₃(FeGa)₅O₁₂ garnets obtained by liquid phase epitaxy on Gd₃Ga₅O₁₂ substrates are discussed in the 920 to 980°C. range. The experiments have been carried out with the substrates in a horizontal plane and with unidirectional rotation ranging from 30 to 300 rotations per minute (rpm). A sharp increase in the growth velocity at temperatures higher than 960°C is interpreted on the basis of a diffusion-reaction theory. It is found that the diffusion constant increases steeper at higher temperatures and that the linear law of the growth rate as a function of the square root of the rotation rate holds to much higher rotation rates at these temperatures. The influence of the surface incorporation is too small to be detectable. The results are compared with published data concerning other compositions.     

X-ray diffraction study on amorphous gallium

Amorphous films of some μm in thickness, prepared by low temperature condensation in an ultra-high vacuum onto liquid helium cooled substrates, have been studied in situ by using an X-ray diffractometer operating in a symmetrical reflection mode. The structure factor of gallium has been obtained over the wavevector range 1.3 to 16.1 Å⁻ by means of two wavelengths, Cr_K and Mo_K, monochromatized by balanced filters. The average number of nearest neighbours deduced from the well-resolved first maximum in the radial distribution function is equal to 9.3 atoms. The results are compared to those previously found by electron diffraction measurements on thin films and also to the structure of supercooled liquid.     

Phase separation and crystallization in amorphous Pd-Si-Sb

It is found that replacing some of the Si in a Pd-Si-Sb glass with Sb can make it more resistant to crystallization than the pure binary material. This is shown by the calorimetric results, in which the crystallization temperature increases and the glass temperature decreases with increasing Sb substitution, and also by the finding that certain alloys, such as Pd_80.5 Si_16.5Sb₃ may be quenched into amorphous rods (by the gradient-quench method) up to 0.5 mm thick.

Calorimetry and small-angle X-ray scattering data show that certain alloys in this system phase separate in the amorphous state. The two phases thus produced independently crystallize. Isothermal measurements indicate that the rate of crystallization of one of the phases is interface-limited, with most nuclei initially present. The other crystallization process does not fit an Avrami law, possibly due to a transformation of the crystalline phase.

A method called “gradient-quenching” (GQ) was used to prepare samples from the melt in such a way that the quench-rate was non-uniform, so all stages of crystallization in slowly-quenched alloys are displayed. Nucleation was frequently found to take place on voids and inclusions.

The use of the calorimetric and GQ methods in conjunction to gather information about crystallization processes in metallic glasses is discussed.     

Incorporation behaviors of group V elements in GaAsSbN grown by gas-source molecular-beam epitaxy

We report the incorporation behaviors of As, Sb, and N atoms in GaAsSbN grown by gas-source molecular-beam epitaxy. We found that N atom is more reactive and competitive than Sb atom at the growth temperature ranging from 420 to 450 °C. The increment in Sb beam flux hardly changes the N composition. However, the increment in N flux retards the incorporation of Sb. In addition, the increment in As₂ flux makes the Sb and N compositions decrease at the same rate. Based on these results, we have successfully grown GaAsSbN epilayers lattice-matched to GaAs substrates. The energy gap at room temperature is as low as 0.803 eV. Negative deviation from Vegard's law in lattice constant is observed in these layers.     

An X-ray diffraction study of the structure of B2O3---Cs2O liquids

The short range structures of B₂O₃ (90 mol%)---Cs₂O (10 mol%) and B₂O₃ (80 mol%)---Cs₂O (20 mol%) liquids were analyzed at 973 and 1053 K, respectively, by an X-ray diffraction method, and the effects of Cs₂O addition on the boron-oxygen bonding were investigated. The existence of BO₃ triangles, which form the so-called boroxol ring structure, was confirmed in B₂O₃---Cs₂O liquids, as well as in B₂O₃ liquid, but some fraction of the BO₃ triangles was thought to be converted to BO₄ tetrahedra. Similar results have previously been observed also in B₂O₃---Cs₂O glasses. A Cs atom was found to be surrounded by six O atoms; four Cs---O interatomic distances were about 3.2 Å but the other two were at 3.8–3.9 Å. These distances indicate that distorted Cs---O octahedra may exist in these B₂O₃---Cs₂O liquids.     

Study on PbWO4 doped with Y, Sb

A series of PbWO₄(PWO) powders, undoped and doped with Y and or Sb, were prepared in air and studied by cathodoluminescence, photoluminescence excitation and emission spectra, and compared with that of undoped and Sb doped PWO single crystals grown by the Bridgman method. The luminescence of PWO prepared in air at high temperature (900° C) is mainly in a broad green band, and its intensity of emission is stronger than that of doped PWO. However the luminescence of PWO:Sb prepared in an oxygen deficient atmosphere is better than undoped PWO.     

Photoinduced structural changes in antimony polyphosphate based glasses

A photocontraction effect in amorphous films of the binary glass system 0.20 [Sb(PO₃)₃]_n–0.80 Sb₂O₃ has been observed after UV irradiation using the 350.7 nm Kr⁺ ion laser line with 5.0 W/cm². Good optical quality films up to 4.0 μm were deposited on silica substrates at room temperature in vacuum by electron beam physical vapor deposition (EB-PVD) and characterized using WDX, XRD, optical absorption, infrared reflectance, profilometry and atomic force microscopy (AFM) techniques. Very stable glasses were prepared by the melt quenching technique and used as evaporation source for the production of films. The photoinduced structural change (PSC) was observed as a variation of about 6% in the film thickness and this effect is accompanied by a photobleaching of the irradiated area with a blue shift of the optical absorption edge. Otherwise this photoinduced change in the film thickness is very sensitive to the variations in the shape and intensity of the laser beam; therefore several possibilities in optical recording arise from these results.     

Thermal stability and crystallization kinetics of new As–Ge–Se–Sb glasses

Thermal stability and crystallization kinetics of As₁₄Ge₁₄Se_72−xSb_x (where x = 3, 6, 9, 12 and 15 at.%) glasses are studied by the differential scanning calorimetry. The values of the glass transition temperature (T_g) and the peak temperature of crystallization (T_p) are found to be dependent on heating rate and antimony content. From the heating rate dependence of T_g and T_p the values of the activation energy for glass transition (E_t) and the activation energy for crystallization (E_c) are evaluated and their composition dependence discussed. Crystallization studies have been made under non-isothermal conditions with the samples heated at several uniform rates. Using a recent analysis developed for non-isothermal crystallization studies, information on some aspects of the crystallization process has been obtained. The stability calculations emphasized that the thermal stability decreases with increasing the Sb content.