气相输运合成PbI2多晶的热力学研究

本文对PbI2合成反应体系的反应焓变,反应熵增,Gibbs自由能变化和反应平衡常数进行了理论计算,从热力学角度论证了选取PbI2熔点(678K)以上的723K作为体系合成反应控制温度的可行性.在723K的控温工艺下,采用两温区气相输运方法合成出高纯、单相的PbI2多晶材料,XRD分析结果表明符合热力学计算结果的控温工艺能有效地应用于PbI2多晶合成.     

CdSiP2多晶合成的热力学研究

采用离子型化合物函数模型,对CdSiP2多晶合成过程的反应焓、熵、Gibbs自由能以及化学平衡常数等热力学参数进行了计算,在1473 K合成CdSiP2多晶时,系统的焓变ΔrHT<0,熵增加值ΔrST为负,Gibbs自由能ΔrGT=-29.68 kJ/mol,平衡常数KT=11.289。结果表明:在1473 K合成CdSiP2多晶,化合反应速率很大,反应充分,产物生成率高,系统趋于稳定。根据计算结果提供的温度1473 K进行CdSiP2多晶合成实验,获得了外观呈紫红色,完整致密的多晶锭,经X射线衍射和光电子能谱分析表明,合成产物为高纯、单相的CdSiP2多晶材料。采用合成的多晶料为原料进行单晶生长,获得了结晶性较好的CdSiP2单晶体。     

Synthesis and characterization of PbI2 polycrystals

Single‐phase PbI₂ polycrystalline material for single crystal growth was synthesized by two‐temperature vapor‐transporting method (TVM), directly from highly pure lead and iodine with excess lead without according to the PbI₂ stoichiometry. It is found that there is an immiscible phenomenon of two melts in the synthesis experiment, and the melts solidified until cooled down to room temperature. X‐ray diffraction (XRD) analysis and Energy dispersive X‐ray (EDX) microanalysis indicate that the solidified materials are single‐phase PbI₂ polycrystal and nearly pure lead. Considering the observed immiscible phenomenon and the data given in paper [1], it is able to confirm that there is a new immiscible region L₂+L₃ in Pb‐I phase diagram, which is very important to PbI₂ polycrystal synthesis and single crystal growth. Using single‐phase PbI₂ polycrystalline material synthesized by our method, PbI₂ single crystal with size of ?15mm×30mm was grown by vertical Bridgman method. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Synthesis of nano‐crystalline zeolite β: Effects of crystallization parameters

The effects of variation in Si/Al ratio (25 and 100) and crystallization temperature (80 °C to 180 °C, at an interval of 20 K) on crystal size of zeolite β were studied. Products obtained at different synthesis parameters were characterized by powder X‐ray diffraction, IR spectroscopy, thermal analysis, scanning electron microscopy and nitrogen adsorption. Increase in crystal size with crystallization temperature and Si/Al molar ratio was observed. Crystal morphology at 140 °C was spherical whereas at 180 °C it was of irregular shape. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

AgGa1-xInxSe2单晶的生长研究

采用高纯(99.9999;)Ag、Ga、In和Se单质为原料,按化学计量比富Se0.3～0.5;配料,通过机械振荡和温度振荡相结合的方法合成出单相高致密AgGa1-xInxSe2多晶材料.以此为原料采用布里奇曼法生长出外观完整的尺寸为φ15mm×25mm的AgGa1-xInxSe2单晶锭(x=0.2).沿自然显露面对晶体进行了解理和X射线衍射分析,发现该面是(101)面.同时进行了红外透过率测试,其红外透过率为41;.     

Electrical Resistivity and Thermally Stimulated Current in CuIn5Se8

From electrical resistivity measurements in the range from 240 to 450 K and from optical absorption measurements the energy gap value of CuIn₅Se₈ has been found to be 1.13 eV. Thermally stimulated current and electrical measurements at high temperature performed in indium annealed samples show deep levels at 0.55 and 0.79 eV, respectively. These defects are expected to be associated with interstitial indium or indium in copper site because of the In‐rich condition.     

Microwave irradiation solvothermal technique: an optimized protocol for size‐control synthesis of Ru nanoparticles

Ruthenium (III) chloride salt and Poly (N‐vinyl‐2‐pyrrolidone) (PVP as a capping agent) was dissolved in ethylene glycol, which played a dual role for synthesis, as solvent and also as reducing agent. Microwave (MW) irradiation was applied to the solvent which provided controllable thermal activation for synthesis of ruthenium nanoparticles and also restricted the agglomeration of particles in presence of excess amount of solvent, which was recovered by distillation after completion of reaction. Synthesized particle was found to be in the range of 2–20 nm with narrow size distribution and average particle size was around 14 nm. Particle size and size distribution were studied by varying different parameters e.g. reaction temperature, time, PVP/RuCl₃ molar ratio and irradiation power and was characterized by Transmission electron microscopy (TEM). Mathematical model has been developed using matlab software to obtain the particle size as a function of microwave power.     

Carrier Transport Properties of InS Single Crystals

The electrical resistivity and Hall effect of indium sulfide single crystals are measured in the temperature range from 25 to 350 K. The donor energy levels located at 500, 40 and 10 meV below the conduction band are identified from both measurements. The data analysis of the temperature‐dependent Hall effect measurements revealed a carrier effective mass of 0.95 m₀, a carrier compensation ratio of 0.9 and an acoustic deformation potential of 6 eV. The Hall mobility data are analyzed assuming the carrier scattering by acoustic and polar optical phonons, and ionized impurities.     

Electrical properties of amorphous and crystalline InSb and InAs thin films

Amorphous films of indium antimonide (0.02–0.26 μm) and indium arsenide (0.03–0.3 μm) were formed on goldseal glass, freshly cleaved mica and NaCl substrates by using a “flash evaporation” technique. The post-deposition heat treatment was carried out on these films when the amorphous → crystalline transformation was observed. The transformation was characterized by a sudden and large fall in the resistance of the film at a particular temperature depending on the thickness. This transformation was confirmed by transmission electron micrographs and diffraction patterns obtained on the films before and after heat treatment. The transformation temperatures lie between 495–525 K for indium antimonide and 550–575 K for indium aresenide, for the thickness range involved in our investigations. The electrical conductivity measurements showed a temperature dependent activation in the high temperature region and hopping conduction in the low temperature region (Mott's theory). The activation energies, at different temperatures for various thicknesses were calculated and presented. While no Hall mobility could be observed in as-deposited films, very low mobilities were observed in annealed thick films (t > 2000 Å). Thermoelectric power for InSb films was found to vary from 0.075–0.17 mV/K for films of thickness ranging from 1000–2300 Å, whereas for InAs films, its value varied from 0.09–0.27 mV/K for the thickness range, 1250–2500 Å. These measurements indicated the conductivity to be n-type and supported the hopping conduction mechanism observed in low temperature conductivity measurements.     

Stability of ruthenium nanoparticles synthesized by solvothermal method

One of the major obstacles to the synthesis of nanoparticles and nanocatalyst is the stability of particles. In the present study, polymer stabilized ruthenium nanoparticles were synthesized by solvothermal method using solutions of ruthenium chloride in ethylene glycol in presence of poly(N ‐vinyl‐2‐pyrrolidone) (PVP) as a stabilizing agent. Stability of nanoparticles was studied by varying different parameters e.g. PVP/RuCl₃ molar raio, RuCl₃ concentration, reaction temperature and time and expressed in terms of particle size and size distribution. Transmission electron microscope (TEM) analysis revealed the presence of metallic clusters with a uniform size of about 20‐65 nm. Dispersion destabilisation of colloidal nanoparticles was detected by Turbiscan. Polymer stabilized ruthenium nanoparticles were dispersed on γ‐alumina to prepare uniformly disperse Ru/γ‐Al₂O₃ catalyst by mechanical strirring and sonication. Inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), X‐Ray powder diffraction (XRD), Transmission electron microscopy (TEM) and Thermo gravimetric analysis (TGA) were used to characterize the supported catalyst. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

ZnGeAs2多晶合成与表征

ZnGeAs2是黄铜矿结构的三元化合物半导体材料,在红外非线性光学方面有重要应用前景.本文探讨了ZnGeAs2多晶的形成途径和合成机理,报道了一种ZnGeAs2多晶合成方法.以高纯(6N)Zn、Ge、As单质为原料,按化学计量比,富Zn1‰和As2‰配料,采用双温区合成方法,辅以机械、温度振荡和梯度降温的合成工艺,合成出均匀致密的单相ZnGeAs2多晶.经XRD和EDS分析表明:合成产物为黄铜矿结构的单相ZnGeAs2多晶,晶胞常数为a=b=0.56745 nm,c=1.11580 nm,与标准PDF卡片(No.730397)一致;各组成元素的原子比Zn∶Ge∶AS=1.00∶0.98∶1.95,接近理想化学计量比.上述分析结果表明,合成产物可用于ZnGeAs2单晶生长,为进一步研究ZnGeAs2晶体的非线性光学性能和应用奠定了较好的基础.     

Electrical conductivity of sulfamic acid single crystals

Single crystals of sulfamic acid have been grown by the method of slow evaporation at constant temperature. DC electrical conductivity was measured in the temperature range 300 ‐ 440 K along a, b and c‐axes. Conductivity measurements show slope change near 330 K and 410 K. The slope change observed around 330 K may be attributed as due to a phase transition which has been well supported by the DSC and DTA measurements. Slope change observed around 410 K is attributed as the onset of the thermal decomcoposition as evidenced by TGA curve. TGA studies show the crystal is very stable up to 440 K. Activation energies for the conduction process are calculated for all measured crystallographic directions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

T(x) phase diagram of the CuSbS2–CuInS2 system and solubility limit of Sb in CuInS2

The starting ternary compounds CuInS₂ and CuSbS₂ and alloys of the CuSbS₂–CuInS₂ system with the molar fractions of CuInS₂ (x) equal to 0.05, 0.15, 0.25, 0.375, 0.50, 0.625, 0.75, 0.85, and 0.95 were prepared and the phase relations in this system were investigated by X‐ray powder diffraction, optical microscopy, scanning electron microscopy, and differential thermal analysis. It was shown that the T–x phase diagram of the CuInS₂–CuSbS₂ system has a eutectic character with the eutectic temperature of 807 K. The alloys of the CuSbS₂–CuInS₂ system with the molar fraction of CuInS₂ in the range from 0.038 to 0.941 at room temperature are two‐phased, and the limits of solubility are 0.059 molar fractions for CuSbS₂ in CuInS₂ and 0.038 molar fractions for CuInS₂ in CuSbS₂.     

Synthesis of mercuric iodide and bismuth tri‐iodide nanoparticles for heavy metal iodide films nucleation

We synthesized mercuric iodide and bismuth tri‐iodide nanoparticles by suspension in octadecene, from Hg(NO₃)₂.H₂O and I₂, and from Bi(NO₃)₃.5H₂O and I₂, respectively. The best synthesis conditions were 2 h at 70‐80 °C, followed by 10 min at 110 °C for mercuric iodide nanoparticles, and 4 h at 80‐110 °C, followed by 10 min at 180‐210 °C for bismuth tri‐iodide ones. Nanoparticles were then washed and centrifuged with ether repeatedly. Compounds identity was confirmed by X‐ray diffraction (XRD) and energy dispersive spectrometry (EDS). We found shifts of the X‐ray diffraction maxima for nanoparticles of both compounds. We characterized the nanoparticles by transmission (TEM) and scanning (SEM) electron microscopy. We obtained disk‐like and squared mercuric iodide nanostructures, 80‐140 nm and 100‐125 nm in size respectively. We also obtained rounded and rod‐like bismuth tri‐iodide nanoparticles, 30‐500 nm in size. Acetonitrile and isopropanol suspensions of mercuric iodide nanoparticles, and acetonitrile suspension of bismuth tri‐iodide nanoparticles exhibited peak maxima shifts in their UV‐Vis spectra. We synthesized for the first time mercuric iodide and bismuth tri‐iodide nanoparticles by the suspension method, although we have not yet obtained uniform shape and size distributions. They offer interesting perspectives for crystalline film nucleation and for improving current applications of these materials, as well as for opening new ones. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth,composition, ferroelectric and magnetic properties of new multiferroic Pb3.3Mn4.8Ni1.1Ti0.56O15.3 single crystals

Multiferroic single crystals in the novel system Pb‐Mn‐Ni‐Ti‐O have been grown by the high temperature solution growth method. At room temperature the crystals are indexed in the hexagonal space group P6₃cm. The dielectric and magnetic properties along with the temperature dependence of the c‐lattice parameter have been studied in the temperature range 2 K ‐ 500 К. The magnetic measurements reveal a paramagnetic to antiferromagnetic phase transition around 48 K. The dielectric permittivity exhibits a maximum at 430 K, indicating ferroelectric to paraelectric phase transition. The temperature dependent Raman and XRD measurements around 430 K reveal an anomaly and abrupt change of the lattice parameter along the z‐axis respectively, thus confirming the ferroelectric‐to‐paraelectric phase transition.     

Synthesis and growth mechanism of ZnO rod‐like nanostructures by a microwave‐assisted low‐temperature aqueous solution route

A zinc oxide (ZnO) nanoarray (rod‐like nanostructure) was successfully synthesized through a low‐temperature aqueous solution and microwave‐assisted synthesis using zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetramine (HMTA) as raw materials, and using FTO glass as substrate. The effects of parameters in the preparation process, such as solution concentration, reaction temperature and microwave power, on the morphology and microstructure of ZnO nanoarray were studied. Phase structure and morphology of the products were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results indicated that hexagonal wurtzite structure ZnO nanoarray with good crystallization could be prepared through a low‐temperature solution method. When the concentration of the mixed solution was 0.05 M, the reaction temperature was 95 °C, and the reaction time was 4 h, high‐density ZnO regular nanorods of 200 nm diameter were obtained. A possible mechanism with different synthesis methods and the influence of microwave processing are also proposed in this paper.     

Intermediates and transport phenomena in two‐temperature synthesis of ZnGeP2

High quality semiconducting ternary compound ZnGeP₂ was synthesized by a modified two‐temperature technique using high purity elemental zinc, germanium and phosphorus as the starting materials. Transport phenomena of zinc and phosphorus vapors and the major reaction intermediates, taking place in ZnGeP₂ formation, were studied by interrupting the synthesis process using quenching technique as well as by adjusting the temperatures of cold and hot zones. The powder X‐ray diffraction analysis showed that the major reaction intermediates were ZnP₂, Zn₃P₂, and GeP, which proportions were changed at the different temperature stages. ZnP₂ was formed in the temperature gradient region and ZnGeP₂ was formed in the hot zone when the temperature of the hot zone was higher than 900 °C. The 520‐1040 °C temperature profile was chosen for the ZnGeP₂ synthesis and charge amount per run reached 200 g. The powder X‐ray diffraction pattern of the synthesized ZnGeP₂ compound was in agreement with the standard pattern of ZnGeP₂. These results demonstrated that the synthesized ZnGeP₂ compound was a single phase. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Calorimetric and phase equilibria studies of the Ni–Sn–Bi system

The phase equilibria at 1273 K were investigated and an isothermal section of the Ni‐Sn‐Bi phase diagram was constructed. The phase boundaries are inclined to the Bi‐rich region that is agreement with phase equilibria at lower temperatures. The molar enthalpies of formation of liquid ternary Ni–Sn–Bi alloys have been determined at 833, 873 and 933 K by direct reaction calorimetry using pellets of 325 mesh powders of pure Ni, Sn and Bi. Measurements were performed with alloys containing from 0.05 to 0.10 mole fractions of nickel, and at ratios of tin and bismuth mole fractions X_Sn/X_Bi = 2.8, 1.2 and 0.43. The experimental calorimetric data were used to calculate a regular solutions parameter of the ternary liquid phase by means of two different thermodynamic data files. It was found that the Ni–Sn–Bi ternary liquid phase could be described as temperature independent ternary regular solution. The assessed values of the ternary interaction parameter are ‐280 J·mol^–1 and 56 000 J·mol^–1, depending on the binary parameters used. Enthalpies of formation of solid binary phases were measured, too. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Rapid Synthesis of Polycrystalline CuGa1‐xInxTe2 Compounds

A series of CuGa_1‐xIn_xTe₂ bulk quaternary compounds (x=0.17, 0.33, 0.50, 0.67, 0.83) has been synthesized from the corresponding stoichiometric melts by a rapid cooling procedure. The same procedure was used to obtain the ternary bulk compounds CuGaTe₂ and CuInTe₂ with the aim to compare, according the Vegard law, the match between molar fraction of the indium (x) and the lattice parameters for the aforementioned quaternary compounds. The nature of the crystalline phases, the local structure homogeneity and stoichiometry of these compounds have been investigated by x‐ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The analysis revealed the presence of the chalcopyritic structure for all the samples.     

Synthesis of superconducting sphere‐like Mo2C nanoparticles in an autoclave

Sphere‐like Mo₂C nanoparticles have been synthesized through the reaction of sodium molybdate, anhydrous ethanol and sodium azide at 450 °C for 10 h in a sealed stainless steel autoclave. X‐ray powder diffraction results indicated that the final product was Mo₂C. Transmission electron microscopy (TEM) and scanning elctron microscopy (SEM) were employed to characterize the as‐prepared sample. The sample was mostly composed of sphere‐like particles, which has a superconducting transition temperature of 9.5 K, and its calculated surface area is 30.859 m²/g. The experimental parameters such as reaction temperature and reactants were studied to investigate the reaction mechanism. It was found that sodium azide and reaction temperature played key roles in the formation of sphere‐like Mo₂C nanoparticles. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)