Structure and magnetic properties of Pr0. 1CexTb0.9-xFe1.9 alloys

1　INTRODUCTIONTerfenol D ( Tb0.27 Dy0.73 Fe2 ) exhibits largemagentostriction and minimized magnetic anisotro py at room temperature[1], so it is widely used inactuators and transducers. But the main raw mate rials of Terfenol D are expensive Tb and Dy. Ac cording to the single ion model[2], CeFe2 and PrFe2compounds have larger magnetostriction thanTbFe2 and DyFe2 at 0 K. In addition, Ce and Prare much cheaper than Tb and Dy. So Ce basedand Pr based compo…     

Giant magneto-impedance and permeability in Fe89Zr6Hf1B4 ribbons

1 Introduction The Giant magneto-impedance (GMI) effect has been attracted much attention due to its potential ap-plication in magnetic heads and sensors [1-10]. It has been suggested that the GMI effect can be at-tributed to combinations of the skin effe…     

Hydrogen desorption kinetics of amorphous Mg0.9Ti0. 1Ni1-xPdx （x=0, 0.05, 0.1 and 0.15） electrode alloys

1 Introduction Mg-based alloy is a kind of promising hydrogen storage materials used for fuel cell. It is also a potential candidate as cathode materials of Ni-MH rechargeable batteries due to its large discharge capacity[1]. However, its cyclic stabilit…     

Magnetoresistance and magnetization of La2／3 （Ca0. 60 Ba0. 40 ） 1／3 MnO3 in different temperature ranges

A polycrystalline La2/3 (Ca0. 60 Ba0. 40 ) 1/3 MnO3 was prepared by standard solid reaction method. Magnetization(M) and magnetoresistance of the sample were measured between T= 77 K and 350 K. It is found that some correlations exist in the external field dependency of the magnetoresistance magnetoresistance and M in the low and high temperature regions. Moreover, there are different magnetic field dependence of magnetoresistance and magnetization in different temperature ranges, which indicates the presence of different magnetoresistance mechanisms.Based on the models of spin-polarized tunneling and percolation model, the simulated magnetoresistance obtained using Monte Carlo method well explains the experimental fact.     

Structural evolution of spray-formed Al-70wt.%Si alloys during isothermal holding in the semi-solid state

1 Introduction The study on semi-solid behavior of metals and alloys was pioneered by Spencor and his co-workers at MIT in 1971 [1]. Since then the semi-solid proc- essing (SSP) has been widely studied and used as forming process compared with other methods [2-3]. The materials under the semi-solid state are de- formed much more easily, however they will still maintain the shape and certain strength. SSP can in- crease the part-forming rate, reduce the thermal shock imposed on the mould, i…     

A NEW INTELLIGENT AMPEROMETRIC TYPE OF ELECTROCHEMICAL HYDROGEN PROBE

1.IntroductionHydrogeninducedcracking(HIC)orsulfidesstresscorrosioncracking(SSCC)ofsteeloftenoccursinvariousindustrialprocesseswiththepermeationofhydrogenintothesteel[1].Susceptibilityofsteeltothisphenomenonmainlydependsonmetallurgicalandenvironmenta...     

国外文献题录

表面科学进展(542C0009)02040040 电子跃迁诱发离子表面纳米级的变质处 理[刊,英].2001,67(1-8):123～138 02040041表面物理学的下一个25年展望[刊,英]. 2001,67(1-8):17～44     

Aluminum ion beam surface modification of elastic metallic-plastic pads for improving tribological properties

1INTRODUCTION Theelasticmetallic plasticpads(EMP)arewidelyusedinverticalelectricmachinesofhydro powerplants.ThesurfacematerialofEMPis PTFE.ThePTFEhaslowfrictioncoefficientand excellentinsulativity,butthestrength,hardnessandwear resistantpropertiesarenotsatisfacto ry[1].Inordertoimprovethestrength,hardness andwear resistantcharacterofPTFE,somephysi calcomminglingmethodsareused[24].Inrecentyears,therehasbeenever increasing interestinthesurfacemodificationofpolymerstoimprovetheirchemi…     

Effect of preparation conditions on properties of Al-substituted α-Ni（OH）2 prepared by homogeneous precipitation

1INTRODUCTION Nickelhydroxideiswidelyusedasthepositive electrodematerialofNi MH,Ni CdandNi Zn batteries.ItcrystallizesintwopolymorphicformsknownasαNi(OH)2andβNi(OH)2.Duringelec trochemicalcycles,therearetworeversiblereac tionsofnickelhydroxide,namely,α(Ⅱ)γ(Ⅲ)andβ(Ⅱ)β(Ⅲ),respectively[1].However,γNiOOHformsinthelongcyclingprocessofβ(Ⅱ)β(Ⅲ),whichresultsinthemechanicalexpan sionandpoorelectrodepropertiesduetodifferentinterlaminardistancesbetweenγNiOOHandβNiOOH[2].Th…     

Amorphous and nano-crystalline structures of mechanically-alloyed Al-24.4?(mole fraction) powder mixture

1INTRODUCTI0NMechanicalalloying(MA)isaball-millingprocessrelatedtorepeatedfracturingandreweldingofpowderparticles['].Kochetalre-portedf0rthefirsttimetheprel,arationofamor-phousNieoNb#oPowderbyMAofelementalpowdersin1983[2].Sincethen,considerablestudiesonthepreparationofnon-equilibriumphasessuchasamorphous['~'],supersaturatedsolid..l.ti...[61andmetastablecompounds['3havebeencarriedout.Inthepreviouspa-pers["'],nanometerordercrystallinestructuresandmetastablephasesinAl-Feall0ysformedduring…     

不同晶粒尺寸的(La0.47Gd0.2)Sr0.33MnO3纳米颗粒磁性能

采用非晶态多核配合的方法制备了(La0.47Gd0.2)Sr0.33MnO3纳米颗粒,用XRD、HRTEM和MPMS等手段对纳米颗粒的微观结构和磁性能进行研究。XRD和SAD分析表明,所有的样品都具有单相钙钛矿结构;TEM分析表明, 经过600,800和1000 ℃烧结10 h后的样品颗粒尺寸分别为40~50 nm,90~100 nm和140~150 nm。样品的磁学性能结果表明：(La0.47Gd0.2)Sr0.33MnO3纳米颗粒的居里温度TC (298 K)基本上不随颗粒尺寸的变化而变化,而相对磁制冷能力取决于颗粒尺寸;颗粒尺寸为90~100 nm的(La0.47Gd0.2)Sr0.33MnO3纳米颗粒的相对磁制冷能力最大,可以作为室温下使用的磁制冷工质侯选材料。     

(La0.57Dy0.1)Sr0.33MnO3多晶纳米颗粒的磁热性能

采用非晶态前驱体的方法在800 ℃的低温下制备出(La0.57Dy0.1)Sr0.33MnO3纳米颗粒,用XRD、HRTEM和MPMS等手段对纳米颗粒的微观结构和磁性能进行研究.XRD和ED分析表明,所有的样品都具有单相钙钛矿结构;通过对样品不同温度下等温磁场的测量和计算,发现在居里温度点(358 K) (La0.57Dy0.1)Sr0.33MnO3纳米颗粒的最大磁熵变随着磁场的增加而增加,即使在5 T磁场下也没有达到饱和;居里温度附近纳米颗粒具有较大的磁热效应和较宽的峰值温度范围,这些良好性能可能和纳米颗粒具有大的表面和界面有关.     

La_（0.85）K_（0.15）MnO_3多晶纳米颗粒磁制冷材料的制备

采用非晶态多核配合的方法在800℃制备出La0.85K0.15MnO3纳米颗粒,用XRD、HRTEM和PPMS等手段对纳米颗粒的微观结构和磁性能进行研究。XRD和ED分析表明,所有样品都具有单相钙钛矿结构;样品的M-T曲线研究结果表明,La0.85K0.15MnO3纳米颗粒的居里温度TC为242.65 K。     

Sr掺杂对La_（0.77-x）Ca_（0.2）Sr_xMnO_3系列材料的相结构和居里温度的影响

以存在La空位的钙钛矿材料La0.77Ca0.2MnO3为母体,用溶胶-凝胶法制备了La0.77-xCa0.2SrxMnO3（x=0.00,0.02,0.06,0.08,0.10）系列样品,研究表明,该系列材料均为单相钙钛矿结构,且随Sr2＋含量的增加,该系列材料的晶格发生畸变,同时居里温度单调递增,由236K增高至300K,覆盖整个室温区,这对材料的实际应用有重要意义。     

Emissivity of La1-xSrxMnO3/acrylic Resin Thermal Control Coating

Thermal control coatings were fabricated by mixing of La1-xSrxMnO3(LSMO)powder and acrylic resin and brushed on Al alloy substrate.The powders of La0.7Sr0.3MnO3 and La0.8Sr0.2MnO3 were prepared using sol-gel method.XRD results reveal the phase structure of LSMO powders are perovskite.The transition temperature from metal to insulator of La0.7Sr0.3MnO3 and La0.8Sr0.2MnO3 are 300 and 275 K,respectively.The emissivity evolution with temperature of the coatings was measured.For La0.7Sr0.3MnO3/acrylic resin coating,the emissivity increases from 0.56 to 0.88,and for La0.7Sr0.3MnO3/acrylic resin coating from 0.50 to 0.90.     

Enhanced room temperature magnetoresistance in maganites La0.60Sr0.25-yNa0.15Δy MnO 31

Bulk polycrystalline samples of La0.60Sr0.4MnO3 and La0.60Sr0.25-yNa0.15ΔyMnO3 with 0.00≤ y ≤0.15 ("Δ" representing cation vacancy) were successfully synthesized using the sol-gel method. The structural, magnetic, and electrical properties of the polycrystallineof the samples were investigated. The results of X-ray powder diffraction patterns show that these compounds crystallize in a distorted rhombohedral structure with the space group R(3)C . The measurement shows that, with vacancy content y increasing, the unit cell volume V of samples increases, furthermore, the Curie temperature TC decreases. The temperature dependence of resistivity shows that all samples undergo a metal-semiconductor transition accompanying a ferromagnetic to paramagnetic transition with the increase of temperature. Under an applied filed of 1.8 T, a maximum room temperature magnetoresistance ( MR ) of 20% is obtained at 293 K for the compound La0.60Sr0.1Na0.15Δ0.15MnO3. The MR peak value of La0.60Sr0.1Na0.15Δ0.15MnO3 increases2 times more than that of La0.60Sr0.40MnO3 ( MRP=6.4%, TMR =373 K), and the MR peak is shifted from 373 K to room temperature.     

La0.7Sr0.3MnO3和ZnO异质结的量子铁磁自旋特性

采用脉冲激光沉积方法制备La0.7Sr0.3MnO3/ZnO异质结,并对其量子铁磁自旋行为进行研究。发现掺杂浓度可有效调整长程的电子自旋和轨道的相互作用,以及短程小极化子的相互作用程度。LSMO/ZnO异质结构可对能带进行有效剪裁。XRD结果表明,所制样品具有良好的晶格外延特性。伏安特性和阻温曲线显示异质结具有半金属光导特性。在激光光场和磁场下测试La0.7Sr0.3MnO3/ZnO异质结量子铁磁自旋磁阻及光阻。结果发现,样品x=0.3在Tp=250K发生金属绝缘体相变而呈现半金属特性,在Tc=175K温度发生顺磁到反铁磁相变。连续激光下低于峰值温度220K和脉冲激光下低于175K区域激光光场导致光致退磁,光阻增大,在大于峰值温度Tp的高温区出现光阻降低。研究表明,在光场下La0.7Sr0.3MnO3/ZnO异质结特性受界面电子自旋取向和载流子浓度调控,态密度以及自旋轨道作用会导致光致阻抗变化,这些影响与LSMO/ZnO异质结的极化和界面应力所产生的界面态缺陷结构有关。     

Infrared Spectra of La_(0.65)Ba_xMnO_(3-δ) Oxides

l 71liv t[.olk li.us,/illun(}iall) suP)orled b} lhe Trans--Cei1lDrJ Foundalion ()j' lhe Mu(f'tlIioiIal MiIli.vIF1 t)/' China an(l bylhe N'IIit)nal NIlur(Il ScIi.ncc Found'l/it)n '1f Chl)la.1* C()rresponding auth()r E-l11ailf Jthu @ sdu.edu.cn1 IntroductionRecently, colossal magnetoresistance CMRin perovskite manganese oxides La,--,A,MnO,with an Mn3 /Mn4 mixed valence has becomea topic of considerable interest[l--3]. Theseoxides exhibit semiconducting behavior in theparamagnetic …     

Cr doping effect in B-site of La0.75Sr0.25MnO3 on its phase stability and performance as an SOFC anode

La0.75Sr0.25CryMn1-yO3(LSCM) (y=0.0-0.6) composite oxides were synthesized by a complexing process of combining ethylene diamine tetraacetic acid (EDTA) and citrate. X-ray diffraction (XRD), temperamre-programmed reduction, electrical conductivity, I-V polarization, and impedance spectroscopy were conducted to investigate the Cr doping effect of La0.75Sr0.25MnO3 on its phase stability and electrochemical performance as a solid-oxide fuel cell (SOFC) anode. The chemical and structural stabilities of the oxides increased steadily with increasing Cr doping concentration, while the electrical conductivity decreased on the contrary. At y ≥ 0.4, the basic perovskite structure under the an-ode operating condition was sustained. A cell with 0.5-mm-thick scandia-stabilized zirconia electrolyte and La0.75Sr0.25CryMn1-yO3 anode de-livered a power density of～15 mW.cm-2 at 850℃.     

Influence of Gd Doping on Magnetic Behavior in La0.67Sr0.33CoO3, La0.67Sr0.33MnO3

研究了La0.67-xGdxSr0.33CoO3、La0.67-xGdxSr0.33MnO3 (x=0.00, 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.67)体系的M-T曲线、M-H曲线。结果表明:随Gd掺杂浓度增高,La0.67-xGdxSr0.33CoO3体系的磁结构表现为团簇玻璃态,x>0.10样品的M-T曲线出现了低温区M值急剧上升的奇特现象;La0.67-xGdxSr0.33MnO3体系的磁结构从长程铁磁有序向团簇玻璃态、反铁磁状态转变,x≥0.50样品的M-T曲线在低温区急剧下降。两种体系呈现的不同现象,来源于Gd与Co、Mn不同的耦合作用和Co的自旋态的转变。