Analysis of magnetic mechanisms of 3d-doped ZnO diluted magnetic semiconductors by an abnormal peak on M-T curve

The crystallographic structures and magnetic properties of a Zn0.95Co0.05O thin film deposited on a C-sapphire substrate using a dual-beam pulsed laser deposition method were characterized. It was shown from crystallographic analysis that the film belongs to the wurtzite structure with the C-axis aligned with that of the substrate. Magnetic hysteresis loops were observed till up to room temperature. A small peak around 55 K was noticed on the magnetization vs. temperature curve. The corresponding temperature of the small peak is close to that of ‘the abnormal peak’ reported by X.M. Zhang et al. From the results obtained, no correlation was found between the abnormal peak and the quantum effects. The magnetic behaviors in the Zn0.95Co0.05O film cannot be explained by the ferromagnetism in diluted magnetic semiconductors. The magnetic mechanisms in ZnO-based diluted magnetic semiconductors are also discussed.     

Preparation and performance of LiNi0. 8Co0.2O2 cathode material based on Co-substituted α-Ni（OH）2 precursor

Co-substituted α-Ni（OH）2 was synthesized by a novel microwave homogeneous precipitation method in the presence of urea. LiNi0.8Co0.2O2 cathode material was synthesized by calcining Co-substituted α-Ni（OH）2 precursor and LiOH·H2O at 900℃for 10 h in flowing oxygen. XRD, FTIR, FESEM and electrochemical tests were used to study the physical and the electrochemical performances of the materials. The results show that the prepared LiNi0.8Co0.2O2 compound has a good layered hexagonal structure. Moreover, the LiNi0.8Co0.2O2cathode material demonstrates stable cyclability with a high initial specific discharge capacity of 183.9 mAh/g. The good electrochemical performance could be attributed to the uniform distribution of Ni^2＋ and Co^2＋ ions in the crystal structure and a minimal cation mixing in LiNi0.8Co0.2O2 host structure.     

High quality p-type ZnO film growth by a simple method and its properties

P-type ZnO：N films have been grown successfully by chemical vapor deposition （CVD） using Zn4（OH）2（O2CCH3）6·2H2O as the solid source material and ZnNO3 as the doping source material. XPS, Hall-effect measurement and PL spectra were employed to analyze the structural, electrical and optical properties and study the influence of substrate temperature on the film. Results showed that with a lower substrate temperature, the film exhibited p-type conduction and its resistivity decreased when the substrete temperature increased. When the substrates temperature was 400℃, p-type ZnO films were obtained with carrier concentration of ＋5.127×10^17 cm^-3, resistivity of 0.04706 Ω· cm and Hall mobility of 259 cm^2/（V·s）; they still exhibited p-type conduction after a month. When the substrate temperature was too high, the film was transformed from p-type to n-type conduction.     

Structural and electrical properties of ZnO films on freestanding thick diamond films

In this paper, ZnO films are deposited on freestanding thick diamond films （FTDF） by plasma-assisted metal organic chemical vapour deposition （MOCVD）. Diethyl zinc （DEZn）, O2 and N2O are applied as precursors and different substrate temperatures are used to achieve high quality ZnO films. The influence of substrate temperature on the properties of ZnO films is systematically investigated by X-ray diffraction （XRD）, Hall measurements and electron probe microanalysis （EPMA）. Experimental results demonstrate that ZnO films deposited at 600℃ and 73 Pa display a fine electrical quality and Zn/O atomic ratio plays an important role in the electrical property of ZnO films.     

Metal oxide and hydroxide nanoarrays: Hydrothermal synthes is and applications as superc apacitors and nanocatalysts

The development of nanotechnology in recent decades has brought new opportunities in the exploration of new materials for solving the issues of fossil fuel consumption and environment pollution.Materials with nano-array architecture are emerging as the key due to their structure advantages,which offer the possibility to fabricate high-performance electrochemical electrodes and catalysts for both energy storage and effcient use of energy.The main challenges in this feld remain as rational structure design and corresponding controllable synthesis.This article reviews recent progress in our laboratory related to the hydrothermal synthesis of metal oxide and hydroxide nanoarrays,whose structures are designed aiming to the application on supercapacitors and catalysts.The strategies for developing advanced materials of metal oxide and hydroxide nanoarrays,including NiO,Ni(OH)2,Co3O4,Co3O4@Ni–Co–O,cobalt carbonate hydroxide array,and mixed metal oxide arrays like Co3 xFex O4and Znx Co3 xO4,are discussed.The different kinds of structure designs such as 1D nanorod,2D nanowall and hierarchical arrays were involved to meet the needs of the high performance materials.Finally,the future trends and perspectives in the development of advanced nanoarrays materials are highlighted.     

The first principle calculation of elemental-vacancy-assisted modifications on structural properties and optical responses of ZnO system

The structural properties and optical responses of ZnO_0.94 and Zn_0.94O systems as the possible models of ZnO system containing elemental defect states were studied using the plane-wave method within the generalized gradient approximation. The pristine ZnO system was used as the reference. The simulated XRD patterns showed the three highest intensity for (100), (002), and (101) orientations for all the systems. Compared to O vacancy, Zn vacancy mostly provided higher structure factor shifts of ZnO system. Moreover, the strongest local-symmetry distortion at ZnO₄ tetrahedra was implied in Zn_0.94O system. The optical responses showed that all the systems exhibited the optical dichroism based on the extinction coefficient spectra. Interestingly, Zn_0.94O system showed the lowest energy levels of absorption and high-reflectance edges. Additionally, the highest saturation threshold energy of the effective number of valence electrons was obtained for this system. The result emphasizes the importance of Zn vacancy in providing the significant effect on the optical responses of ZnO system.     

Fe掺杂对Zn1 xCoxO纳米晶体结构及磁性行为的影响

利用溶胶-凝胶法制备了Fe掺杂Zn1 xCoxO(x=001~002)纳米晶体.通过XRD,TEM和VSM对其结构、晶格参数和磁性进行了表征和分析.所有样品都没有检测到非晶态产物以及Fe,Co团簇等第二相,即Fe掺杂没有改变Zn1 xCoxO晶体的纤锌矿型ZnO结构、晶粒度大小以及室温铁磁性.随着Fe掺杂浓度的提高,饱和磁化强度、剩余磁化强度和矫顽力等磁性参数都有相应的改善.Fe掺杂还引起了交换偏置,并且,该现象随着Fe掺杂浓度的提高而增强;但是,单原子Fe对饱和磁化强度的贡献低于单原子Co对自发磁化强度的贡献,这表明Fe,Co共掺杂ZnO材料与Co掺杂ZnO材料的磁性机制有所不同.     

Thermodynamics and phase transformations in the recovery of zinc from willemite

Willemite is a common component of zinc and lead metallurgical slags that, in the absence of effective utilization methods, cause serious environmental problems. To solve this problem and increase zinc recovery, we proposed a novel extraction method of zinc from willemite by calcified roasting followed by leaching in NH₄Cl-NH₃·H₂O solution. The thermodynamics and phase conversion of Zn₂SiO₄ to zinc oxide (ZnO) during calcified roasting with CaO were investigated. The mechanism of mineralogical phase conversion and the effects of the CaO-to-Zn₂SiO₄ mole ratio (n(CaO)/n(Zn₂SiO₄)), roasting temperature, and the roasting time on zinc-bearing phase conversion were experimentally investigated. The results show that Zn₂SiO₄ was first converted to Ca₂ZnSi₂O₇ and then to ZnO. The critical step in extracting zinc from willemite is the conversion of Zn₂SiO₄ to ZnO. The zinc percent leached in the ammonia leaching system rapidly increased because of the gradual complete phase conversion from willemite to ZnO via the calcified roasting process.     

Measurement of GaAs start duration in different solution concentration using infrared images

This paper proposes a new infrared method to measure the start duration of GaAs substrate in chemical etching. When etching starts, the temperature of liquid-film will change because of heat release in the chemical reaction. As a result, the start duration of GaAs can be tested by collecting real-time in-frared thermal images in the course of temperature variation. Both theoretical analysis and experi-mental results show that the line shape liquid film of a 2-mm width is a good monitoring subject. By making use of the grey distribution change of a certain cross section of the line shape liquid film, the start duration of reaction between GaAs and H2SO4-H202-H20 is obtained. The start durations of reac-tion between GaAs substrate and H2SO4： H202： H20 （=5：1：50 and 15：3：50） solution are about 0.2 s and 0.3-0.4 s, respectively. This result and relative method will impulse the research of wet chemical etching technology of GaAs and so on.     

Dead lithium phase investigation of Sn-Zn alloy as anode materials for lithium ion battery

In this work, based on First-principle plane wave pseudo-potential method, we have carried out an in-depth study on the possible dead lithium phase of Sn-Zn alloy as anode materials for lithium ion batteries. Through investigation, we found that the phases Li_xSn₄Zn₄(x = 2, 4, 6, 8) contributed to reversible capacity, while the phases Li_xSn₄Zn_8−(x−4)(x = 4.74, 7.72) led to capacity loss due to high formation energy, namely, they were the dead lithium phases during the charge/discharge process. And we come up with a new idea that stable lithium alloy phase with high lithiation formation energy (dead lithium phase) can also result in high loss of active lithium ion, besides the traditional expression that the formation of solid electrolyte interface film leads to high capacity loss. Supported by the National Natural Science Foundation of China (Grant No. 50771046), Natural Science Foundation of Guangdong Province (Grant No. 05200534), Key Projects of Guangdong Province and Guangzhou City (Grant Nos. 2006A10704003 and 2006Z3-D2031) and China Postdoctoral Science Foundation (Project No. 20080440764)     

Preparation and magnetic properties of CoFe2O4/TiO2 composite films

Using （Ti（OC4H9）4） and metal chlorates as starting materials, CoFe2O4/TiO2 composite films were prepared by sol-gel method. The effects of heat treatment temperature and pH of the precursor on microstructure and magnetic properties were studied. The phase structure of the samples was examined by X-ray diffraction. The microstructure was examined by scanning electron microscope, atomic force microscope and polarized microscope. The magnetic property was measured by vibrating sample magnetometer. The results show that the crystals of different phases grow up independently. CoFe2O4 is uniformly embedded into the TiO2 matrix in the prepared composite films, and the growth of composite films is dependent on the heat treatment temperatures and PH of the precursor. The average size of CoFe2O4 crystal is 19 nm in Nanocomposite film prepared when the heat treatment temperature is 800℃ and the pH of the precursor is between 2 and 3. The magnetism of the composite films is enhanced as the heat treatment temperature increases.     

Low-field positive and high-field negative magnetoresistances in multiphase Fe-oxide thin films at room temperature

Multiphase Fe-oxide thin films are fabricated on glass substrates by a facing-target sputtering tech- nique. X-ray diffraction and X-ray photoelectron spectroscopy reveal that Fe, Fe3BO4, γ -Fe2BO3B and FeO coexist in the films. High resolution transmission electron microscopy shows the well-defined colum- nar grain structure with the unoxidized Fe as the core and iron-oxide as the shell. The low-field positive and high-field negative magnetoresistances coexist in such a system at room temperature, which can be explained by considering a shell/core model. Nonlinear current-voltage curve and photovoltaic effect further confirm the tunneling-type conduction.     

THz spectra of five borates crystals

Terahertz spectral responses have been studied for five borate crystals Nas[B2P3O13] （NBP）, Zn3BPO （ZBP）, SrB407 （SBO）, Na3LagO3（BO 3）8 （NLBO） and PbB407 （PBO）. It is found that the samples had good transmission in 0.25--1.5 THz region. Both SBO and NLBO have an absorption coefficient less than 10 cm^-1. Among them, SBO has not only the smallest absorption coefficient but also a very flat dispersion in the frequency region under investigation. Distinct resonance absorption peaks are observed for ZBP at v1 = 1.4 THz, v2 = 2.0 THz and SBO at v = 2.4 THz. In the spectrum of PBO, two abnormal dispersions appear in the frequency regions 1.44--1.74 and 2.2--2.5 THz. The absorption coefficients and refraction indices of the five crystals are extracted from the THz time-domain （THz-TDS） spectra in 0.25--2.5 THz region. The properties and origins of the spectral responses are addressed.     

Enhancement of magnetism of Zn0.95Co0.05O films by p-type Cu+ doping

Organic solar cells withμ-oxo-bridged gallium phthalocyanine dimer(GaPc dimer) and fullerene were produced by an evaporation method.A device based on the GaPc dimer provided a conversion efficiency of 4.2×10~(-3)%,which is better compared to a device based on phthalocyanine monomer.Dimerization effect was discussed with a molecular orbital calculation,and the crystalline phases of the present solar cells were investigated by X-ray diffraction.Further improvement of the efficiency was discussed on the bas...     

Heteroseneous oxidation of carbonyl sulfide on mineral oxides

Heterogeneous oxidation of carbonyl sulfide （OCS） on mineral oxides including SiO2, Fe2O3, CaO, MgO, ZnO and TiO2, which are the main components of atmospheric particles, were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy （in situ DRIFTS）, ion chromatography （IC）, temperature-programmed desorption （TPD）, X-ray diffraction （XRD） and Brunauer-Emmett-Teller （BET） methods. The main products and intermediates of the heterogeneous oxidation of OCS on these oxides were identified with in situ DRIFTS and IC. The reaction mechanism and kinetics were also discussed. It is found that the reaction mechanism on these mineral oxides is the same as that on Al2O3 for the same final products and the intermediates at room temperature. Namely, OCS can be catalytically oxidized to produce surface SO4^2- species and gaseous CO2 through the surface hydrogen thiocarbonate （HSCO2-） and HSO; species. The activity series for heterogeneous oxidation of OCS follows： Al2O3 ≈ CaO 〉 MgO 〉 TiO2 ≈ ZnO 〉 Fe2O3 〉 SiO2. The specific area, basic hydroxyl and surface basicity of these oxides have effect on the reactivity. This study suggests that heterogeneous reactions of OCS on mineral dust may be an unneglectable sink of OCS.     

Structure of aqueous sodium sulfate solutions derived from X-ray diffraction

A rapid liquid X-ray diffractometer was used to study the time-averaged and space-averaged structure of aqueous sodium sulfate solutions at 298 and 323 K. Difference radial distribution functions of the solutions were obtained from accurate diffraction data. The interaction distances of Na^＋-OH2 and S-H2O in solutions were found to be 0.235 and 0.385 nm, respectively, after deconvolution of superposition peaks by Gaussian multi-peak fitting program. The characteristic distance of the NaSO; contact ion pairs in higher concentration solutions was determined to be 0.345 nm, suggesting that the Na^＋ ions coordinated with SO4^2- ions in the mono-dentate form. Effects of concentration and temperature on the hydration structure of the solutions were discussed in the present paper. With a decrease in concentration, the contributions of the H2O to the diffraction pattern increase, the average coordination number of the Na^＋ ions hardly changes, while the hydration number of SO4^2- ions increases slightly. The formation of NaSO; contact ion pairs becomes easier at higher temperature. The structure of hydrogen bond in dilute solutions is broken to a considerable extent with rising temperature, and the peak at 0.290 nm splits into two peaks at 0.275 and 0.305 nm, respectively.     

Single-negative properties of Ba2Co1.8Cu0.2Fe12O22 and Ba3Co2Fe23.4Zn0.6O41 hexagonal ferrites

The electromagnetic properties of Ba₂Co_1.8Cu_0.2Fe₁₂O₂₂ (Co₂Y) and Ba₃Co₂Fe_23.4Zn_0.6O₄₁ (Co₂Z) were studied by measuring microwave scattering parameters. In the transmission spectra of Ba₂Co_1.8Cu_0.2Fe₁₂O₂₂, a forbidden band emerges due to ferromagnetic resonance, and the permeability will turn to negative in the vicinity of the ferromagnetic resonance frequency. In the complex permittivity spectra of Ba₃Co₂Fe_23.4Zn_0.6O₄₁, the negative permittivity can be obtained due to dielectric resonance. Therefore, Co₂Y and Co₂Z can be used to construct left-handed materials possessing negative permeability and negative permittivity simultaneously.     

Improved electrochemica l properties by lithium insertion into Co3O4 in aqueous LiOH solution

Co₃O₄ microspheres were synthesized by a simple hydrothermal treatment.The first-cycle charge-discharge tests were carried out between-0.6 and 0.6 V vs.SCE.The pristine,discharged and recharged specimens were characterized by X-ray power diffraction and scanning electron microscopy.Cyclic voltammetry（CV） curves of Co₃O₄ at various concentrations in LiOH solution were investigated.The appearance of the two pairs of redox peaks indicated that two sets of faradaic reactions were involved in the redox reactions of Co₃O₄ to LiCoO₂ and LiHCoO₂.     

Influence of O2/Ar ratio on the properties of transparent conductive niobium-doped ZnO films

Niobium-doped ZnO transparent conductive films are deposited on glass substrates by radio frequency sputtering at 300℃. The influence of O2/Ar ratio on the structural, electrical and optical properties of the as-deposited films is investigated by X-ray diffraction, Hall measurement and optical transmission spectroscopy. The lowest resistivity of 4.0×10^-4Ω· cm is obtained from the film deposited at the O2/Ar ratio of 1/12. The average optical transmittance of the films is over 90%.     

中温SOFC阴极材料La0.7Sr0.3Co1-xCuxO3-δ的制备及性能

采用固相反应法制备了La_0.7Sr_0.3Co_1-xCu_xO_3-δ系列中温固体氧化物燃料电池（SOFC）阴极材料粉体.对其进行晶体结构表征,高温电导率和热膨胀曲线测试,并选取其中性能较好的样品进行了单电池实验.结果表明,Cu的掺杂降低了（La,Sr）CoO La₃体系阴极材料的热膨胀系数,在x=0.05时电导率略高于未掺Cu的样品.以La_0.7Sr_0.3Co_0.95Cu _0.05O _3-δ为阴极、Ce_0.8Sm_0.2O_1.9为电解质组成的SOFC单电池,在850℃最大短路电流密度达511mA/cm²,最大输出功率密度约为0.106W/cm².