Exchange Coupling and Magnetic Behavior of SmCo_(5-x)Sn_x Alloys

Exchange coupling and magnetic properties of SmCo5 alloys containing different amounts of Sn were investigated in sintered magnets.X-ray diffraction analysis revealed the formation of Sm2Co17 and Sm2Co7 phases in SmCo5 matrix.Exchange coupling mechanism was evaluated by switching field distribution,dcdemagnetization and magnetization curves as function of reverse applied field.Energy product of 59.2 kJ/m 3(7.4 MGOe),remanent magnetization to maximum magnetization ratio of 0.97 and remanence coercivity to intrinsic coercivity ratio of 1.75 were achieved for 0.2 at.% Sn.     

Magnetic and Electrical Behavior of MnTe_(1-x)Sb_x Alloys

The structure,specific heat,magnetic and electrical properties of MnTe1-xSbx(x=0,0.1,0.15,0.2 and 0.25) alloys have been investigated.The MnTe1-xSbx alloys crystallize in a hexagonal NiAs-type structure,and the impurity of MnSb phase appears when x≥0.15.The MnTe0.9Sb0.1 compound exhibits ferrimagnetic behavior with hysteresis loops even at 350 K,showing that the magnetic properties of MnTe compound are very sensitive to little compositional change.The ferromagnetism in the MnTe1-xSbx alloys with higher Sb contents may be attributed to the impurity of MnSb phase.Energy dispersive X-ray spectroscopy analysis on the MnTe0.9Sb0.1 compound indicates that Sb is very difficult to dope into the lattice of MnTe.So the anomaly of resistivity at 300 K of MnTe0.9Sb0.1 and the peak of specific heat around 304 K of all the alloys are thought to be related with the antiferromagnetic interactions of MnTe-based lattice.     

四元Heusler合金Co_2[Mn,Fe]Ge_(1-x)Ga_x的晶体结构、半金属稳定性和磁性

基于密度泛函理论的第一性原理研究了四元Heusler合金Co2MnGe1-xGax和Co2FeGe1-xGax的晶体结构、半金属稳定性和磁性,发现随着掺入Ga比例x的改变,其晶格常数遵循Vigard原理。对于Co2MnGa1-xGex系列的合金,其原胞磁矩很好地符合SP(Slater-Pauling)值和实验值;而对于Co2MnGe1-xGax系列合金,其原胞磁矩虽然与实验值一致,但却随x的减小而逐渐偏离SP值。态密度显示,Co2MnGe1-xGax系列合金在x=0～0.75的掺杂比例内都有0.4～0.6eV的自旋向下带带隙宽度,而Co2FeGe1-xGax虽然在费米面附近也存在较高的自旋极化,但几乎不存在显著的自旋向下带带隙。此外,四元合金Co2MnGe0.75Ga0.25的费米面居于最小自旋带隙的中部,将具有较好的半金属稳定性。     

静电纺丝法制备Sr1-xLaxFe12-xCoxO19纳米纤维及其磁性研究

采用溶胶?凝胶过程和静电纺丝技术相结合的方法,制得了PVP/Sr1-xLaxFe12-xCoxO19(x=0～0.5)复合纳米纤维,经过煅烧处理过程,获得了Sr1-xLaxFe12-xCoxO19(x=0～0.5)纳米纤维.通过SEM、TEM、XRD和VSM等技术对样品的形貌、物相、结构以及磁性能进行了表征.结果表明,800℃煅烧后的Sr1-xLaxFe12-xCoxO19(x=0.5)纳米纤维的直径主要分布在80～150 nm;这些纤维在室温下都具有硬磁特性,化学组成对铁氧体的磁性能有着显著的影响,当x≥0.3时,样品中同时出现M型的SrFe12O19、LaFeO3和CoFe2O4;在适当范围内(x≤0.1),La3+-Co2+的掺杂有利于改善锶铁氧体纤维的永磁性能,相应的矫顽力、饱和磁化强度和剩余磁化强度分别为Hc=432.02kA/m,Ms=54.7A.m2/kg,Mr=28.9A.m2/kg,与传统溶胶?凝胶法在相同条件下制得的Sr0.9La0.1Fe11.9Co0.1O19粉体样品相比,磁性能也有显著提高.     

Properties of Evaporated Si_(1-x)Sn_x and Si_(1_x)Sn_x:H Amorphous Alloys

Amorphous Si_(1-x)Sn_x alloys have been prepared by co-evaporation onto substrates maintained atliquid nitrogen temperature. Their atomic structure is investigated using density measurements,scanning high-energy electron diffraction and Mossbauer spectroscopy. The optical and electricalproperties are reported. Then, a method to hydrogenate the films during the evaporation process isdescribed and applied to the preparation of amorphous semiconductors from pure silicon to pure tin.Finally, multilayers of type Si / Si:H / ... or Si:H / Si:D / ... are studied. The modulation of hydrogen isshown by low-angle neutron scattering and measurements of hydrogen diffusivity are presented.     

Preparation and Thermoelectric Properties of Zr_(1-x)Ti_xNiSn_(0.975)Sb_(0.025) Half-Heusler Alloys

Zr1-xTixNiSn0.975Sb0.025 (x=0, 0.15, 0.25, 0.5) half-Heusler thermoelectric materials have been prepared by levitation melt, melt spinning and hot pressing. X-ray diffraction analysis and scanning electron microscopy observation showed that nearly single phase half-Heusler compounds were obtained for the levitation-melted ingots. The effects of Ti substitution and grain refinement by melt spinning have been studied. It is found that both the Ti substitution on the Zr site and the grain refinement can reduce...     

La_（1－x）SrxCoO_（3－y）导电陶瓷制备工艺的研究

用固相反应法制备了Ｌａ＿（１－ｘ）Ｓｒ＿ｘＣｏＯ＿（３－ｙ）导电陶瓷材料，研究了制备工艺对烧结性能的影响。实验结果表明：烧结体的致密度取决于预烧温度、烧成温度及保温时间，此外还与成型方法等因素有关。在１０００～１３００℃保温２～１５ｈ获得了高密度、导电性良好的立方钙钛矿型Ｌａ＿（１－ｘ）Ｓｒ＿ｘＣｏＯ＿（３－ｙ）（ｘ＝０．５，０．６）陶瓷材料。用Ｘ射线分析了材料的相组成和结构。     

Influence of Small Cr Addition on Thermal Stability and Magnetic Properties of Fe-Co-Zr-Nb-B Glassy Alloys

Fe62Cos-xCrxZr6Nb4B20 （x=0-4 at. pct） metallic glasses show high thermal stability with a maximum supercooled liquid region of about 84.8 K. The addition of 2 at. pct Cr causes the extension of the supercooled liquid region remarkably, leading to the enhancement of thermal stability and glass-forming ability. The crystallization of the Fe-based glassy alloys takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such as α-Fe, Fe2Zr and ZrB2. The long-range atomic rearrangements required for the precipitation of the multiple crystalline phases seem to play an important role in the appearance of the large supercooled liquid region through the retardation of the crystallization reactions. The Fe-based alloys exhibit soft ferromagnetic properties. The saturation magnetization decreases with increasing Cr content while the saturated magnetostriction increases as a function of Cr content. There is no distinct change in the saturation magnetization and coercive force with annealing temperature below the crystallization temperature. The devitrification gives rise to a considerable enhancement in both as and He.     

不同温度烧结的赝两元合金(PbTe)1-x(snTe)x电学性能

首次采用粉末冶金法在大成分范围内制备了赝两元合金(PbTe)_1-x(SnTe)_x(x=0～1),并对其电学性能进行了系统地研究.实验发现:经550℃烧结后,随合金中SnTe摩尔分数x增大,合金的最大Seebeck系数值减小.当摩尔分数x≤0.6时,最大Seebeck系数所对应的温度逐渐升高;摩尔分数x>0.6时基本不变.当摩尔分数x=0.6时电导率达最大值.经高温烧结后两参数值也有类似的变化规律,但摩尔分数>0.2的各合金Seebeck系数值高于550℃烧结后的合金,电导率降低.从而得出:烧结温度对赝两元合金(PbTe)_1-x(SnTe)_x的综合电学性能影响不大.     

磁控溅射法制备Zn_(1-x)Co_xO薄膜的磁性能

采用磁控溅射工艺,在玻璃基片上制备了Zn1-xCoxO(x=0.02~0.15)稀磁半导体薄膜。采用X-射线衍射(XRD)、X射线光电子能谱(XPS)、原子力显微镜(AFM)、振动样品磁强计(VSM)研究了薄膜的相结构、化学成分及价态、表面形貌和磁性能。结果表明,本实验条件下,薄膜不存在Co及Co的氧化物相,薄膜中Zn的化学价为+2,Co则以+2和+4价的形式存在;薄膜晶体结构为c轴取向生长的六方纤锌矿结构;薄膜表面平整致密。在温度为300 K时,Zn0.9Co0.1O薄膜呈铁磁效应,在M-H曲线中观测到明显的磁滞回线特征。     

快速凝固Al_(88)Ce_2Ni_(10-x)Fe_x(x=0,1,3,5)非晶铝合金的形成和热稳定性分析

液淬Al(88)Ce2Ni(10-x)Fex(x＝0,1,3,5)非晶铝合金的形成倾向和热稳定随组元Fe含量的增加，表现出较大的差别：前者趋于降低，后者趋于增大。非晶铝合金的形成和热稳定性是由不同微观机理所决定的，其中3d过渡金属Fe与主量元素Al相异原子之间的强烈相互作用是导致热稳定性提高的主要原因。     

Ni_(1-x)Co_xFe_2O_4铁氧体纳米粉末的磁性能和微波吸收特性

利用柠檬酸溶胶-凝胶自蔓延燃烧法合成了Ni1-xCoxFe2O4(x=0,0.1,0.3,0.5)铁氧体纳米粉末。利用XRD、VSM和矢量网络分析仪测定了粉末样品的晶体结构、磁性能和电磁参数。定性分析了样品的饱和磁化强度、矫顽力、复磁导率和复介电常数随频率和Co含量的变化关系。结果表明,自蔓延的所有粉末样品经过600℃,2h高温退火后均为尖晶石相纳米晶颗粒。随着Co替代量x的增加,样品的自然共振频率先增大后减小,并对微波吸收特性有一定的改善。     

Role of Si Addition on the Crystallization Behavior,Thermal Stability,and Magnetic Properties of the FeNiMoBSi Alloys

Journal of Superconductivity and Novel Magnetism - Effects of Si addition on the amorphous forming ability, thermal stability, and soft magnetic properties of the Fe40Ni38Mo4B18-xSix (x = 0, 2, 4,...     

Fe_x(In_2O_3)_(1-x)磁性颗粒膜的结构及光学性质

用射频溅射法制备了金属 /半导体 Fex(In2 O3) 1-x 颗粒膜。实验结果表明 :纳米尺度的Fe颗粒比较均匀地分布在非晶态母体In2 O3 中。退火可使In2 O3 晶化。该样品在室温下表现出超顺磁驰豫 ,符合Langevin方程。光学测量表明 :嵌Fe的磁性颗粒膜 ,其电子的带间跃迁由In2 O3 的直接跃迁变为间接跃迁 ,基本吸收边红移 ;随磁性增强 ,局域态尾变宽 ,带隙变窄     

高铬铁基纤维的热稳定性和磁性

高铬铁基纤维由Cu-11Fe-4Cr原位复合丝材硝酸法萃取得到.研究了微米级、亚微米级高铬铁基纤维样品的结构和磁性变化规律.采用X射线衍射和扫描电镜观察分析了样品的结构和形貌,采用振动样品磁强计测试了样品的磁性,利用热重-差热分析比较了不同变形量的高铬铁基纤维在空气中的热稳定性.结果表明:在空气中低于600℃加热1h后,高铬铁基纤维保持BCC结构不变,样品的饱和磁化强度均大于100 A·m2·kg-1;经800℃加热1h后,由铁磁性的α-(Fe,Cr)固溶体转变为顺磁性的(Fe,Cr)2O3,样品的饱和磁化强度显著下降.微米级、亚微米级高铬铁基纤维的热稳定性显著高于微米级多晶铁纤维.随着变形量增大,较细的高铬铁基纤维的热稳定性较差.     

Nanostructural control in solution-derived epitaxial Ce(1-x)Gd(x)O(2-y) films

A novel mechanism based on aliovalent doping, allowing fine tuning of the nanostructure and surface topography of solution-derived ceria films, is reported. While under reducing atmospheric conditions, non-doped ceria films are inherently polycrystalline due to an interstitial amorphous Ce(2)C(3) phase that inhibits grain growth, a high quality epitaxial film can be achieved simply by doping with Gd(3+) cations. Gd(3+) [Formula: see text] Ce(4+) substitutions within the lattice are accompanied by charge-compensating oxygen vacancies throughout the volume of the crystallites acting as an efficient vehicle to reduce the barrier for grain boundary motion caused by interstitial Ce(2)C(3). In this way, the original nanostructure is self-purified by pushing the amorphous Ce(2)C(3) phase towards the free surface of the film. Once a full epitaxial cube-on-cube oriented ceria film is obtained, its surface morphology is dictated by the interplay between faceting on low energy {110} and/or {111} pyramidal planes and truncation of those pyramids by (001) ones. The development of the latter requires the suppression of their polar character which is thought to be achieved by charge compensation between the dopand and oxygen along [Formula: see text] directions.     

Comparison of the Thermomagnetic and Thermal Effects duringNanocrystallization of Amorphous Fe_(76.5-x)Cu_1Nb_xSi_(13.5)B_9 Alloys

The results of thermomagnetic (TM) and calorimetric (DSC) measurements have been compared in order to clarify some details of the mechanism of nanophase-formation from Finemet-type precursors with different Nb contents. It was found that the main features of the DSC thermograms (shape, relative separation and amplitude of the exothermic peaks characteristic for the precipitation of the Fe-(Si) solid solution and the transition metal borides) depend mainly on the composition of the precursor glass, and are only slightly affected by the heating rate between 20 and 80 K/min. The amplitude of the uprise of the magnetization in the TM curves (attributed to the precipitation of bcc-Fe(Si) and borides) decreases with increasing Nb-content. The Curietemperature of the precursor glasses. Tc(am1), the remainder amorphous phases, Tc(am2) and the bcc nanophase, Tc(n-Fe) are determined from the thermomagnetic curves. The shape of the TM curves is interpreted on the basis of the reactions describing the crystalIization of the hypo-eutectic Fe-B glasses.     

(1-x)TiO_2-xTa_2O_5薄膜的光学性能研究

TiO2-Ta2O5薄膜是较新颖的光学薄膜,由均匀混合的两种化合物薄膜材料作为膜料研制而成,本文采用离子辅助蒸发的方法,以不同配比的Ta2O5和TiO2混合物为初始膜料在K9玻璃上制备了TiO2-Ta2O5混合薄膜,并对其光学性能进行研究.实验结果表明,TiO2-Ta2O5薄膜在可见光范围内有较高的透射率,消光系数在10-3～10-4数量级,折射率在1.80～2.07范围内变化(550nm),是理想的光学镀膜材料.随着Ta2O5含量从0增加到20%,光学带隙从3.266eV单调增加到3.417eV,并用Kayanuma提出的模型解释了透射谱中吸收边的漂移现象.     

Micro-Alloyed P Optimizes AFA,Thermal Stability,Crystallization Behaviors,and Magnetic Properties of the Novel Fe-Rich FeBCuHf Alloys

Journal of Superconductivity and Novel Magnetism - Low amorphous forming ability (AFA) and weak thermal stability become the main obstacles in adjusting α-Fe crystallization behaviors and...     

回收制备烧结Nd-Fe-B磁体的磁性能与耐热性能

以废旧钕铁硼磁体为原料,采用短流程回收制备技术制备了烧结Nd-Fe-B磁体,通过添加镨钕混合稀土研究了磁体的磁性能和耐热性能.结果表明,在回收磁体中添加2％ PrNd,制备的烧结Nd-Fe-B磁体的剩磁为1.31T、矫顽力为1 474.86 kA/m、磁能积为353.90 kJ/m3.与一次成品相比矫顽力恢复到102％,剩磁恢复到95％,磁能积恢复到90％.在293～393 K范围内未掺杂PrNd磁体的矫顽力温度系数为-0.589 9％/K,掺杂2％PrNd磁体的矫顽力温度系数为-0.556 4％/K,提高了磁体在高温下的耐热性能.这是由于添加混合稀土PrNd增强了主相晶粒间的去磁交换耦合作用,提高了主相的磁晶各向异性场,从而提高了磁体的矫顽力和耐热性能.