Dark-red-emitting CdTe0.5Se0.5/Cd0.5Zn0.5S quantum dots: Effect of chemicals on properties

CdTe_0.5Se_0.5/Cd_0.5Zn_0.5S core/shell quantum dots (QDs) with a tunable photoluminescence (PL) range from yellow to dark red (up to a PL peak wavelength of 683 nm) were fabricated using various reaction systems. The core/shell QDs created in the reaction solution of trioctylamine (TOA) and oleic acid (OA) at 300 °C exhibited narrow PL spectra and a related low PL efficiency (38%). In contrast, the core/shell QDs prepared in the solution of 1-octadecene (ODE) and hexadecylamine (HDA) at 200 °C revealed a high PL efficiency (70%) and broad PL spectra. This phenomenon is ascribed that the precursor of Cd, reaction temperature, solvents, and ligands affected the formation process of the shell. The slow growth rate of the shell in the solution of ODE and HDA made QDs with a high PL efficiency. Metal acetate salts without reaction with HDA led to the core/shell QDs with a broad size distribution.     

New compounds with icosahedral structures of the type Cd14-xP4S24-2xI2x

Cadmium-phosphorus sulphide-halides of the above mixed crystal series with 0≤x≤1 were synthesized from the elements at 680° C and characterized by chemical, thermal and x-ray analysis. The materials are monoclinic, space group Cc, their structures being very similar to that of Cd₄SiS₆ and Cd₄GeS₆ resp. Around 385° C a reversible solid-solid transition into a cubic phase, takes place. Of the end members, Cd₁₄P₄S₂₄ (colorless) and Cd₁₃P₄S₂₂I₂ (yellow), crystals were prepared by sinter-annealing and iodine vapour transport resp. Under certain conditions the latter composition can also be prepared in a cubic form, space group F43m, which is stable at room temperature. The materials are strongly piezoelectric and show second harmonic generation upon irradiation with Nd-laser light, the magnitude of the effect being largest in monoclinic Cd₁₃P₄S₂₂I₂.     

Be-Doped Cu0.5Tl0.5Ba2Ca1(Cu0.5Zn1.5)O8?δ Superconductors

We have enhanced the superconducting properties of newly discovered Cu_0.5Tl_0.5Ba₂Ca₁(Cu_0.5Zn_1.5)O_8−δ superconductor by doping Be at Ca sites. The superconducting properties, such as critical current density, in-field magnetic properties and quantity of diamagnetism, are enhanced by Be doping at the Ca sites. The decreased c-axis length and the volume of the unit cell have shown that the inter-ZnO₂-plane coupling is enhanced. We have not observed any localization of the carriers in the neighborhood of Zn atoms in Cu_0.5Tl_0.5Ba₂Ca_1−y Be _y (Cu_0.5Zn_1.5)O_8−δ (y=0, 0.15, 0.30, 0.45, 0.6) superconductors, as proposed in the previous studies. One must expect such effects if present, through the decreased c-axis length by Be doping. The decreased c-axis length results in enhancement of coherence length and Fermi velocity of the carriers, which in turn result in enhanced superconductivity parameters. The presence of Be at the termination ends of the crystals results in enhanced inter-grain coupling and substantially improved their weak link behavior. The optimization of the carriers in CuO₂/ZnO₂-planes have been found to enhance the T _c (R=0) and the magnitude of diamagnetism in Be-doped samples. Also the softening of phonon modes with the increased Zn doping evidenced the incorporation of Zn at the CuO₂ planar sites.     

复合磁性催化剂β-MnO2/MnxZn1-xFe2O4的制备与表征

采用化学共沉淀法制备了以Mn_xZn_1-x Fe₂O₄为磁性基体的β-MnO₂/Mn_xZn_1-xFe₂O₄复合磁性催化剂,利用XRD、SEM、FTIR和超导量子干涉仪对复合磁性催化剂的结构和性能进行了表征,以罗丹明B （RhB）为模拟污染物,研究了β-MnO₂/Mn_xZn_1-xFe₂O₄的催化活性,并考察了其稳定性。结果表明,球状的β-MnO₂与块状的磁性基体Mn_xZn_1-xFe₂O₄成功复合,且制备的β-MnO₂/Mn_xZn_1-xFe₂O₄复合磁性催化剂具有良好的催化性能和磁学性能。当Mn_xZn_1-xFe₂O₄与β-MnO₂的质量比为20：100时,在2 mL含量为30%的H₂O₂作用下,1 h内β-MnO₂/Mn_xZn_1-xFe₂O₄复合磁性催化剂对100 mL浓度为10 mg/L的RhB降解率（93.9%）远高于纯β-MnO₂（33.7%）;在磁场作用下,β-MnO₂/Mn_xZn_1-xFe₂O₄复合磁性催化剂的回收率为89%,经过5次循环利用之后其对RhB的降解率仍达76%。     

Magnetic and crystallographic properties of Fe1−x(Cu0.5In0.5)xCr2S4 spinels

Fe_1?x(Cu_0.5In_0.5)_xCr₂S₄ spinel powders with 0 ≤ x ≤ 1 were prepared. Their lattice constant (a_o) increases linearly with x from a_o = 0.9995 nm for x = 0 to 1.0065 nm for x = 1. Cu⁺, In³⁺, and Fe²⁺ ions occupy tetrahedral A sites of the spinel lattice and Cr³⁺ ions the octahedral B sites. Spinels with 0 ≤ x ≤ 0.82 are ferrimagnets with Curie temperatures decreasing from 171 K for x = 0 to 116 K for x = 0.82. Spinels with 0.82< x≤ 1 are antiferromagnets with Néel temperatures between 31 K and 36 K. The magnetic moment of Fe_0.18Cu_0.41In_0.41Cr₂S₄ spinels was determined by susceptibility measurements to be 5.85 $\text{μ}{}_{\mathrm{<mtext>B</mtext>}}\text{molecule}$, which is equal to the calculated spin-only magnetic moment.     

PbSbBiS4-Sb2S3 and PbSbBiS4-Bi2S3 joins in the PbS-Sb2S3-Bi2S3 system

Phase equilibria along the PbSbBiS₄-Sb₂S₃ and PbSbBiS₄-Bi₂S₃ joins of the PbS-Sb₂S₃-Bi₂S₃ system have been studied for the first time using differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements, and the phase diagrams of the joins have been mapped out. The joins are shown to be pseudobinary with limited series of terminal solid solutions. The solid solutions are p-type semiconductors.     

Die strukturen von BaGa2S4 und BaAl2S4

The isotypic compounds BaGa₂S₄ and BaAl₂S₄ crystallize in the cubic system, space group Pa3 with the constants: BaGa₂S₄: a = 1268.5±0.4 pm, BaAl₂S₄: a = 1265.0±0.7 pm. BaS₄- resp. AlS₄-tetrahedra are connected by common corners to a threedimensional net. The Ba-ions are located in holes with coordination numbers 6 resp. 12.     

High-pressure substitutions for Cd In Cd2Nb2O7 and Cd2Ta2O7

Substitutions into cadmium niobate of the type Cd_2?xA_xNb₂O₇ (x≤0.5) have been carried out at 58 kbars and 1100°C. The substituting A cations were Mg, Mn, Fe, Co, Ni, Cu, and Zn which are all smaller than Cd. Rhombohedral or triclinic distortions derived from cubic Cd₂Nb₂O₇ were achieved at values of x as low as 0.05. All the substituted phases appear to be centric at room temperature. Analogous substitutions into Cd₂Ta₂O₇ were also made.     

Mössbauer studies of thiospinels VI. The system FexZn1−xCr2S4

The spinel system Fe_xZn_1?xCr₂S₄ with 0 ≦ x ≦ 1 has been prepared in polycristalline form. All samples are p type semiconductors. I.R. spectra have been measured between 200 cm^?1 and 600 cm^?1. Room temperature ⁵⁷Fe-Mössbauer spectra show the typical behaviour of tetrahedral site Fe(II) surrounded by different octahedral site neighbours. In comparison with Mössbauer spectra of the spinel system Fe_1+xCr_2?xS₄ the distribution, 0.01 < y < 0.02, is derived.     

Preparation, characterization and microwave absorption properties of polyaniline/Co0.5Zn0.5Fe2O4 nanocomposite

The polyaniline (PAni)/Co_0.5Zn_0.5Fe₂O₄ nanocomposite was prepared by an in situ polymerization in an aqueous solution. The products were characterized by Fourier transform infrared (FT-IR) spectrometer, ultraviolet-visible (UV-vis) spectrometer, X-ray diffraction (XRD) and transmission electron microscope (TEM). The average particle size of the PAni/Co_0.5Zn_0.5Fe₂O₄ was estimated to be about 70 nm by TEM. The reflection loss (dB) of the nanocomposite was measured at different microwave frequencies in X-band (8.2-12.4 GHz), U-band (12.4-18 GHz) and K-band (18-26.5 GHz) by radar cross-section (RCS) method according to the national standard GJB-2038-94. The results showed the reflection loss of the PAni/Co_0.5Zn_0.5Fe₂O₄ nanocomposite was higher than that of the PAni. The maximum reflection loss of the PAni/Co_0.5Zn_0.5Fe₂O₄ nanocomposite was about −39.9 dB at 22.4 GHz with a bandwidth of 5 GHz (full frequency width at about a half of the peak response). In conclusion, this sample is a good microwave shielding and absorbing materials at higher frequency.     

Fine-grained multiferroic BaTiO3/(Ni0.5Zn0.5)Fe2O4 composite ceramics synthesized by novel powder-in-sol precursor hybrid processing route

Dense, homogeneous, and fine-grained multiferroic BaTiO₃/(Ni_0.5Zn_0.5)Fe₂O₄ composite ceramics are synthesized by a novel powder-in-sol precursor hybrid processing route. This route includes the dispersion of nanosized BaTiO₃ ferroelectric powders prepared via conventional sold-state ceramic process into (Ni_0.5Zn_0.5)Fe₂O₄ ferromagnetic sol-gel precursor prepared via sol-gel wet chemistry process. Uniformly distributed slurry is obtained after ball milling and used in the fabrication of the ceramics with low sintering temperatures. The ceramics show coexistence of ferromagnetic and ferroelectric phases with obvious ferromagnetic and ferroelectric hysteresis loops at room temperature, besides exhibiting excellent magnetic and dielectric properties in a wide range of frequency. The combination of high permeability and permittivity with low losses in the ceramics enables significant miniaturization of electronic devices based on the ceramics.     

Growth and characterization of non-linear optical crystal Cd3Zn3B4O12

Cd₃Zn₃B₄O₁₂ polycrystals were synthesized by solid-state and wet chemical reaction methods. Cd₃Zn₃B₄O₁₂ single crystals with millimeter grade were grown from the self-flux B₂O₃ (Cd:Zn:B = 1:1:1.5); and larger crystals were obtained from the PbO-0.85PbF₂ fluxes easily. As-grown crystals were characterized by differential scanning calorimetry and thermogravimetric, X-ray diffraction, infrared and Raman spectral analysis, respectively. The non-linear optical coefficient of the Cd₃Zn₃B₄O₁₂ crystal is 2.6 times as large as that of KH₂PO₄ crystal. Chemical etching shows that this crystal is very stable in neutral solution and not hygroscopic in air at room temperature.     

Ionic conductivity and crystallographic data for Na2-xCa1-xAlxSiO4 and Na2-xCaSi1-xPxO4 carnegieite phases

Single crystals of Na₂CaSiO₄ prepared at 30 kbar and 1500°C are cubic with $\text{a}\text{= 22.456}\text{A}\text{?}$. The polycrystalline compositions Na_1.9Ca_0.9Al_0.1SiO₄ and Na_1.8CaSi_0.8P_0.2O₄ can also be indexed using $\text{a}\text{= 22.458}\text{and}\text{22.471}\text{A}\text{?}$, respectively. The Ca carnegieites Na₂CaSiO₄, Na_1.9Ca_0.9Al_0.1SiO₄, and Na_1.8CaSi_0.8P_0.2O₄ have Na ion conductivities of only 5?8 × 10^?6 (ω-cm)^?1 at 300°C.     

The effect of Bi1.5Zn0.5Nb0.5Ti1.5O7 cover layer on the dielectric and tunable properties of Ba0.6Sr0.4TiO3/Bi1.5Zn0.5Nb0.5Ti1.5O7 bilayered thin films

Bi_1.5Zn_0.5Nb_0.5Ti_1.5O₇ (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba_0.6Sr_0.4TiO₃ (BST) thin films on the Pt/Ti/SiO₂/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces.     

Effect of PbO-SiO2 and PbO-B2O3 flux systems on the crystalline and magnetic properties of Ni0.5Zn0.5Fe2O4 ferrite prepared from the mixed powders

Lead borate and lead silicate were added to lower the sintering temperature of a Ni_0.5Zn_0.5Fe₂O₄ ferrite prepared from the blend of two types of powders and to homogenize the grain size. 5PbO·SiO₂ and 5PbO·B₂O₃ flux systems were added to lower the sintering temperature and diminish the magnetic loss at high frequencies. The ferrites were studied by bulk density, scanning electron microscopy and impedance analysis. It was found that the addition of PbO markedly accelerated the grain growth, while SiO₂ and B₂O₃ were found to be effective to obstruct the movement of grain boundaries and to minimize the grain size. Doping with PbO in the mixed powders appropriately increased the densification and initial permeability. The ferrite doped with 1% of 5PbO·SiO₂ possessed the lowest loss tangent (tgδ) in the range of 5 M-40 MHz and the highest threshold frequency.     

Magnetic, electrical, and optical properties of (HgS)1.5(Al2S3)0.5?Mn? and (HgS)1.5(In2S3)0.5?Mn? crystals

We have studied the magnetic, electrical, and optical properties of (HgS)_1.5(Al₂S₃)_0.5〈Mn〉 and (HgS)_1.5(In₂S₃)_0.5〈Mn〉 crystals and determined their magnetic and band structure parameters. The magnetic (Faraday method) and transport (four-probe method) properties of the (HgS)_1.5(Al₂S₃)_0.5〈Mn〉 and (HgS)_1.5(In₂S₃)_0.5〈Mn〉 crystals were investigated in the ranges T = 77−300 K and H = 20−320 kA/m. The magnetic susceptibility data suggest that the magnetic properties of the crystals can be understood in terms of Mn-S-Mn-S clusters. The Hall coefficient of the crystals is temperature-independent. The electrical conductivity of (HgS)_1.5(Al₂S₃)_0.5〈Mn〉 varies little with temperature and has a maximum, and that of (HgS)_1.5(In₂S₃)0.5〈Mn〉 shows metallic behavior and is a nearly linear function of temperature. The thermopower of the crystals increases with temperature. Optical data attest to direct allowed interband optical transitions. The magnetic and band structure parameters of the crystals are determined.     

Die strukturen des MgAl2S4 und Mg0.830In2.113S4

MgAl₂S₄ crystallizes in the orthorhombic system, space group Pnma (No 62) with the lattice constants: a=1251.1 ± 0.6 pm, b =722.0 ± 0.4 pm, c=592.1 ± 0.4 pm The compound is isotypic to BeAl₂O₄.Mg_0.830In_2.113S₄ forms the spinel structure, space group Fd3m (No 227) with a=1071.9 ± 0.6 pm.     

球形LiNi0.5-xCo2xMn0.5-xO2的合成及其电化学性能

以化学共沉淀法制备的球形Ni0.5-xCo2cMn0.5-xCO3（x=0.075,0.1,1/6）为前驱体合成了球形锂离子电池正极材料LiNi0.5-xCo2xMn0.5-xO2（x=0.075,0.1,1/6）,研究了钴含量对LiNi0.5-xCo2xMn0.5-xO2的物理性能和电化学性能的影响.SEM研究表明,球形LiNi0.5-xCo2xMn0.5-xO2由许多一次颗粒构成,随着钴含量的增加,产物中一次颗粒增大.XRD分析表明,LiNi0.5-xCo2xMn0.5-xO2均为具有层状结构的纯相物质.电化学性能测试结果显示,LiNi0.5-xCo2xMn0.5-xO2随着钴含量的增加,材料的充放电容量提高,且循环性能变好：0.2C倍率下、2.7～4.3V的电压范围内,LiNi0.425CO0.15Mn0.425O2的放电比容量为145mAh·g^-1、LiNi0.4CO0.2Mn（0.4）O2为150mAh·g^-1、LiNi1/3Co1/3Mn1/3O2为158mAh·g^-1,循环50周期后LiNi0.425CO0.15Mn0.425O2和LiNi0.4Co0.2Mn0.4O2的容量衰减率在3%以内,LiNi1/3Co1/3Mn1/3O2容量无衰减.交流阻抗测试结果表明,随着钴含量的增加,材料阻抗值减小.