Magnetic and Transport Properties of La0.5-x Ndx Ba0.5 CoO3 Compounds

Substituting effects of Nd for La in La0.5Ba0.5CoO3 compounds were studied systematically. The results show that Nd doping does not change the itinerant properties of the Co3d electrons. The molecular magnetic moment of the mate-rials decreases monotonically with increasing Nd dopant. When Nd content x ≥0.45, a magnetic phase separation appears in the materials. When x ≤0.45, the Curie temperature decreases monotonically with increasing Nd dopant. This is due to the size effects of the rare earth ions. The electric resistance measurements show that in the studied temperature range, the conduction of the materials belongs to the thermo-diffusion conduction below the Curie temperature, while it belongs to the variable range hopping conduction of polarons over the Curie temperature.     

Magnetic Transition of La0.8Sr0.2Mn1-xCoxO3（x =0, 0.3, 0.5, 1.0）

A series of rare earth compound oxides with the formula of La0.8Sr0.2Mn1-xCoxO3（ were prepared by the method of citric acid. Structures, figures and magnetic properties of the x=0.0, 0.3, 0.5, 1.0） samples were analyzed by means of XRD, SEM and SQUID. Experiment results prove that all the samples are hexagonal, but their figures and magnetic properties are different. La0.8Sr0.2MnO3 is ferromagnetic. La0.8Sr0.2Mn0.7CO0.3O3 and La0.8Sr0.2Mn0.5Co0.5O3 are ferrimagnetic. La0.8Sr0.2CoO3 is antiferromagnetic. SEM results indicate that the structure of the first three are three-dimensional reticulations which are made up of some small ellipsoids which link up at the head and the end. The fourth sample looks like some dispersed small balls.     

Magnetic Properties of La1-xSrxCoO3 (0≤x≤0.5)

The measurements of temperature dependence of the magnetic susceptibility of La1-xSrxCoO3 perovskite oxides at different Sr doping (0≤x≤0.5) and annealing temperature were presented. For the sample with x=0.1, a shoulder was observed around 150 K, and a peak which is one feature of spin glass appeared around 50 K in the curve of susceptibility versus temperature. The high-temperature(250～420 K)susceptibility fits well with Curie-Weiss law for all samples. Weiss constant and effective magnetic moment were determined and their variations with Sr doping and oxygen annealing condition were obtained. The Weiss constant increases monotonously with Sr content for x>0.2. The values of effective moments were interpreted with the spin state of cobalt ions. Studies on the susceptibilities of the samples with x=0.2 under different preparation temperatures and annealing temperatures show that the rising of sintering temperature and annealing temperature will increase the para-ferromagnetic transition temperature, and reduce the effective moment to normal value. Our result shows that both Co3 and Co4 ions should be in IS state after annealing and the oxygen annealing causes the transition of Co3 spin state from HS to IS.     

Influence of annealing on spin state of cobalt ions in La1-xSrxCoO3（0≤x≤0.5） system

Perovskite oxide La1-xSrxCoO3 (0≤x≤0.5) series were prepared and effect of oxygen annealing on crystal structure and magnetic susceptibility were studied. High-temperature susceptibility could be well fitted by Curie-Weiss law for all Sr-doped samples. Weiss constant and effective magnetic moment were determined, and their variations with Sr doping and oxygen annealing condition were obtained. The result suggested that by assuming that the Co3+ ions were in the intermediate-spin (IS) state, most of the Co4+ ions in the as-prepared samples might be in the high-spin (HS) state, but both the Co3+ and Co4+ ions might be in the IS state after oxygen annealing, which indicated that annealing in flowing oxygen could cause transition of the spin state of Co4+ ions from the HS state to IS state.     

A study on hydrogen storage and electrochemical properties of La_（0.55）Pr_（0.05）Nd_（0.15）Mg_（0.25）Ni_（3.5） （Co_（0.5）Al_（0.5））_x （x=0.0, 0.1, 0.3, 0.5） alloys

The La0.55Pr0.05Nd0.15Mg0.25Ni3.5(Co0.5Al0.5)x(x=0.0, 0.1, 0.3, 0.5) alloys were prepared by magnetic levitation melting under an Ar atmosphere, and the effects of Co and Al on the hydrogen storage and electrochemical properties were systematically investigated by pressure composition isotherms, cyclic voltammetry, Tafel polarization and electrochemical impedance spectroscopy testing. The results showed that the alloy phases were mainly consisted of (La,Pr)(Ni,Co)5, LaMg2Ni9, (La,Nd)2Ni7 and LaNi3 phases, and the cell volumes of (La,Pr)(Ni,Co)5, LaMg2Ni9, (La,Nd)2Ni7 and LaNi3 phases expanded with Co and Al element added. The hydrogen storage capacity initially increased from 1.36 (x=0) to 1.47 wt.% (x=0.3) and then decreased to 1.22 wt.% (x=0.5). The discharge capacity retention and cycle stability of the alloy electrodes were improved with the increase of Co and Al contents. The La0.55Pr0.05Nd0.15Mg0.25Ni3.5(Co0.5Al0.5)0.3 alloy electrode possessed better electrochemical kinetic characteristic.     

快速热压制备(AgSbTe_2)_x(Pb_(0.5)Sn_(0.5)Te)_(1-x)半导体材料及热电性能研究

为了进一步提高PbTe系列合金的热电性能和降低生产成本,采用溶剂热反应合成平均粒度为500 nm的PbTe粉末,以所合成的PbTe粉末为主要原料通过封管熔炼法制备(AgSbTe2)x(Pb0.5SnvTe) 1-x(x=0,0.05,0.1,0.15,0.2)系合金.所得合金锭经过高能球磨制成微米级的超细合金粉,再通过快速热压烧结制备测试用的多晶试样,所有试样的相对密度均达到90%以上.通过XRD和SEM等手段分析材料的物相组成和微观结构,研究x的变化对于该体系材料热电性能(电阻率、Seebeck系数、热导率和ZT值)的影响.研究表明,当X取值为0.1时该体系材料的热电性能得到最优化,在575 K时取得最人的ZT值为1.093.     

Magnetic and Transport Properties of Bi0.5Ca0.5-xLaxFe0.3Mn0.7O3 (x=0, 0.05, 0.10, 0.15, 0.20, 0.25) Prepared by Molten Salt Method

Polycrystallines Bi0.5Ca0.5-xLaxFe0.3Mn0.7O3(x=0, 0.05, 0.10, 0.15, 0.20, 0.25) were prepared by molten salt method and showed perovskite orthorhombic structure with space group Pnma. The magnetic measurements in-dicate that the compounds exhibit antiferromagnetic behavior in a temperature range of 4-300K. The measurements of transport properties suggest that the substitution of La for Ca enhanced the conductivity, and a kink appeared on the curve of temperature dependence of resistivity at 275 K, which is related to the spin-reorientation in the samples.     

La3+掺杂对LiNi0.8Co0.15Al0.05O2结构和电化学性能的影响

采用共沉淀法制备添加了La3+的LiNi_0.8Co_0.15Al_0.05O₂正极材料, 通过XPS、X射线分析仪、扫描电镜、电化学工作站、电池充放电测试系统详细地探讨了不同添加量的La3+对材料的结构、形貌和电化学性能的影响。结果显示, 与无添加的LiNi_0.8Co_0.15Al_0.05O₂正极材料比较, 添加了La3+的材料一次颗粒尺寸更大, 球形度更好且材料的电极R_sf+R_ct阻抗均显示有所降低; 当添加x=0.01时, 材料的大电流循环稳定性得到了较大提升, 1 C条件下经过100次循环后, 添加La3+材料容量保持率为75.81 %, 而未添加材料容量保持率只有49.57 %; 添加了La3+材料制得的电池在0.5、1、5 C倍率下的放电比容量也要明显高于无添加材料。      

锂离子电池正极材料LixNi0.5Mn0.5O2电子结构的第一性原理研究

采用基于密度泛函理论的第一性原理超软贋势平面波法,对LixNi0.5Mn0.5O2的几何结构进行优化,并计算相应的电子结构和平均嵌锂电压.结果表明：x=1时,费米能级上分布着Ni、Mn d轨道电子和部分O2p轨道电子,层状LiNi0.5Mn0.5O2是电子的良导体;O2p轨道与Ni、Mn形成较强的共价键, Ni-O与Mn-O具有相近的键长,抑制了LiNiO2与m-LiMnO2中的因Jahn-Teller效应导致的八面体扭曲,且Mn-O键长在充放电过程中保持不变,材料具有稳定的结构;Li在晶胞中以主要离子态的形式存在,有利于脱嵌与传输.随着锂离子的脱出,材料的带隙增加,导电性能变差.     

Collapse of charge ordering in Bi0.5Sr0.5MnO3 by cation disorder： a magnetic and structural investigation

The structure, transport, and magnetic properties of LaxBi0.5.xSr0.5MnO3 （LBSMO） （x=0.1 and 0.4） were studied through X-ray diffraction, magnetization, and electron spin resonance （ESR） measurements. The structural analysis showed that the LBSMO crystallized in an orthorhombic perovskite structure with Pbnm space group for x=-0.1 and Imma space group for x=0.4 and the highly polarizable 6s^2 lone pair of Bi^3＋ was the ttming factor for the structural variations. Magnetic studies revealed that the replacement of Bi ions by La ions resulted in the collapse high temperature charge ordering state of BSMO and it order Ferro Magnetically （FM） with Tc around 355 and 330 K for x=0.1 and 0.4, respectively. Both ESR, temperature and field dependant magnetization suggested that there was a coexistence of FM and the paramagnetic phases well below Tc and the FM and CO-AFM phases below 250 K of LBSMO.     

Magnetic properties and magnetocaloric effects of manganite (La_0.8Ho_0.2)_2/3Ca_1/3MnO₃ and (La_0.5Ho_0.5)_2/3Ca_1/3MnO₃

We reported the magnetic properties and magnetocaloric effects(MCE) of(La0.8Ho0.2)2/3Ca1/3MnO3 and(La0.5Ho0.5)2/3Ca1/3MnO3 nanoparticles by sol-gel technique.With this method,we were able to obtain the samples with particle diameters ranging from 50 to 200 nm.In the(La1-xHox)2/3Ca1/3MnO3 compound,an external magnetic field induced a magnetic transition from an paramagnetic phase to a ferromagnetic phase above Ts=105-135 K,leading to magnetocaloric effects.The maximum value of ΔSM was 1.19 J/(kg·K) at 100 K and 2.03 J/(kg·K) at 152 K for a magnetic field change of 5 T.Because both samples had large relative cooling power(RCP) and wide δTFWHM,the study on systems with the(La1-xHox)2/3Ca1/3MnO3-related magnetic transitions may open an important field in searching good magnetic materials.     

Anomalous Magnetic Behavior in Phase-separated La0.5 Sr0.5 MnO3 +δ Films

(001)La0.5 Sr0.5MnO3 δ films on (001)LaA1O3 substrates were prepared by using a RF magnetron sputtering with powder target.At low temperature, the films exhibit two phase coexistence, which means that ferromagnetic (FM) clusters are embedded in antiferromagnetic (AFM) matrix.Moreover, a shift in hysteresis loop is unexpectedly observed in this inhomogeneous system.We suggest that the anomalous hysteresis loop may result from the unidirectional exchange anisotropy at the interface between AFM and FM clusters.     

聚苯胺/Co0.5Zn0.5La0.1Fe1.9O4复合材料的表征及电磁损耗

采用原位聚合法制备聚苯胺（Pani）/复合材料,使用X射线衍射仪（XRD）、扫描电子显微镜（TEM）和紫外可见吸收光谱（UV-vis）对复合材料进行了表征。XRD结果表明样品为纯Pani和Pani/Co0.5Zn0.5La0.1Fe1.9O4复合材料,SEM照片可知,纯Pani和Pani/Co0.5Zn0.5La0.1Fe1.9O4粒子的平均粒径分别约为150 nm和500 nm,UV-vis光谱表明Pani/Co0.5Zn0.5La0.1Fe1.9O4苯环上的π-π＊和n-π＊分别红移了13 nm和10 nm.在8.2-12.4GHz测试频率范围内,Pani/Co0.5Zn0.5La0.1Fe1.9O4复合材料的介电损耗角正切（tgε）在0.22-0.34之间,磁损耗正切（tgμ）在0.27-0.35之间.     

Promotion Effect of Lantanum ions on Co／SiO2 Catalysts Prepared via Solvated Metal Atom Impregnation Method

In order to assess the promotional effects of La^3 on CO hydrogenation of Co/SiO2 catalyst, solvated metal atom impregnation (SMAI) method was used to prepare unpromoted 10% (mass fraction) Co/SiO2 and a series of La^3 -promoted 10% (mass fraction) Co/SiO2 catalyst with different La/Co atomic ratios (0.1, 0.3, 0.5). X-ray diffraction (XRD), and CO chemisorption measurements show that the cobalt particle size decreases as the La/Co ratios increase. X-ray photoelectron spectrescopy indicates that cobalt is in zero-valent state for all the samples. Catalytic test shows that the catalytic activity of La^3 -promoted Co/SiO2 in CO hydrogenation is higher than that of unpromoted Co/SiO2, and enhances with the La/Co ratios increase. La^3 promotion also causes the enhanced selectivity of Co/SiO2 catalyst for higher hydrocarbon products.     

XPS Studies on Rare Earth Oxide LSCO／YSZ Electrodes

The X-ray diffraction spectra and X-my photoelectron spectroscopy were measured for Sr-doped Lal-xSrx CoO3 materials with perovskite structure prepared by the solid-state reaction method. The influence of heat-treatment tempera-ture on the average crystal size of Lal-xSrx CoO3 was studied. The surface chemical states of Lal-xSrxCoO3 cathodes with different Sr-doped content were discussed. The experimental results show that average crystal size of Lal-xSrxCoO3 under the condition of heat-treatment in the range of 900- 1200℃ is larger than that at other temperatures, which is of benefit to forming porous electrodes. When La is replaced by Sr gradually, the oxygen vacancy concentration increases. It is of benefit to enhancing the transport property of oxygen ion.     

Growth and Spectral Properties of Crystal Er3+:Y0.5Gd0.5VO4

Er3 :Y0.5Gd0.5VO4 crystal with good optical quality was grown by Czochraski method. The structure of the crystal was determined by X-ray powder diffraction method. The segregation coefficient of Er3 ions in the crystal was measured by the ICP method. The absorption and emission spectra were also measured. On the basis of the spectra, the absorption cross-sections, emission spectrum FWHM and fluorescence lifetime of the crystal were calculated. From the properties mentioned above.     

LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2的制备及其性能研究

采用二次高温煅烧法制备了三元复合正极材料LiNi0.5Co0.2Mn0.3O2,用SEM、XRD和蓝电测试仪等对其结构和物理化学性能进行表征和测定。结果表明,材料具有较好的层状结构,在2.75~4.25V下0.2C放电容量达到151mAh/g,经50次充放电循环后,放电容量仍为初始放电容量的93%,放电容量保持率较高,是一种电化学性能优良的三元正极复合材料。     

容量型锂离子电池正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2的合成

采用共沉淀法合成Ni_(0.5)Co_(0.2)Mn_(0.3)(OH)_2前驱体,将前驱体和LiOH混合均匀后经高温煅烧合成了锂离子电池正极材料LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2,并对其进行电化学性能检测。试验表明,制备的电池在电压2.8～4.3V(vs.Li/Li+)区间内,0.1C倍率下的首次库伦效率为88.4%;在1C倍率下循环100次后,放电比容量为157.7mAh/g,容量保持率为96.6%。     

Study on BSTO/MgO Ferroelectric Materials for Phase Shift Doped with Rare Earth Oxides

Phasedarrayantennascansteerthetransmitted orreceivedsignalswiththeadvantagesoffastscan ning,multipletargetstrackingandgoodanti jam ming.Theseantennasarecurrentlyconstructedusing ferritephaseshiftingelements,whicharecostly,large andheavy.Therefore,theirmil…     

Effect of praseodymium and cobalt substitution on magnetic properties and structures in La(Fe_(1–x)Si_x)_(13) compounds

Magnetic properties and structures in La1-zPrz(Fe0.895–xCoxSi0.105)13 (x=0.07, 0.08; z=0, 0.2, 0.4) compounds were investigated. When Pr and Co substituted for La and Fe, the Curie temperature of the compounds was adjusted to around room temperature. The magnetic phase transition was driven from first-order to second-order due to Co substitution. As a second-order phase transition material, the MCE of La0.6Pr0.4(Fe0.825Co0.07Si0.105)13, whose relative cooling power was 175 J/kg under a field change of 2 T, ...