反铁磁性交换作用对(Ga,TM)As居里温度的影响

基于Zener模型,详细分析了反铁磁性交换作用对(Ga,TM)As(TM=Sc,Ti,V,Cr,Mn,Fe,Co,Ni)居里温度的影响,结果表明,反铁磁性交换作用对n型半导体居里温度的影响程度远远大于对p型半导体居里温度的影响,而且在考虑了反铁磁性交换作用后,除了(Ga,Cr)As和(Ga,Mn)As以外都不可能实现室温铁磁性,(Ga,Cr)As和(Ga,Mn)As的掺杂浓度为13.1%和18%时可获得室温铁磁性,但是反铁磁性交换作用相对强弱增强到y=0.01时,任何掺杂浓度都不能实现室温铁磁性。     

Co掺杂对CeO_2显微结构及磁性能的影响

近年来宽禁带稀磁性氧化物半导体由于其高的居里温度在自旋电子学领域受到广泛的关注.用固相反应法制备Co掺杂的CeO2稀磁性氧化物半导体,研究了Co掺杂对其显微形貌及磁性能的影响.结果表明,1300℃烧结的样品结晶形态明显,晶粒较大,结构致密,密度最高;掺杂Co的CeO2样品都具有很好的室温铁磁性,且饱和磁化强度Ms随Co浓度的增加先增大后减小;1300℃烧结、掺3at%Co的Ce0.97Co0.03O2具有最强的室温铁磁性(0.23μB/Co).     

p型ZnO薄膜的研究新进展

ZnO是一种很有前途的宽带隙半导体材料,在光电器件的应用上,实现高质量的p型掺杂是其关键所在。迄今,已有大量p型掺杂ZnO薄膜的研究报道,但是要获得高质量的可重复的p型ZnO薄膜却十分困难。本文就p型ZnO薄膜的掺杂最新研究进展进行了详细论述,并展望了其制备前景。     

过渡族金属掺杂ZnO薄膜的晶体结构和磁性能

采用电子束蒸发法制备了过渡族金属(Fe、Co、Cu)掺杂ZnO薄膜。分析和研究了衬底温度以及Cu掺杂量对薄膜相结构的影响,获得沿c轴高度择尤取向的高质量ZnO薄膜。采用原子力显微镜(AFM)观察薄膜的显微结构,利用所得的图象信息对薄膜进行分析,发现400℃的衬底温度对硅衬底薄膜是合适的,与XRD分析相吻合。通过对薄膜磁性能的分析和研究,得出一些有意义的结果:适量Fe、Co离子掺杂的ZnO薄膜,在室温下具有铁磁性,而在此基础上掺入少量的Cu离子能改善薄膜的磁性能。     

ZnO基紫外光透明导电薄膜的研究进展

ZnO是一种宽禁带半导体材料,通过阳离子Al^3＋掺杂可以改善其导电性,而且通过掺杂MgO进行“能带剪裁”可以实现从紫外到可见光范围内的完全透明。因此,ZnO基紫外光透明导电薄膜近年来逐渐成为半导体光电材料与器件的研究热点之一。本文介绍了紫外光透明导电薄膜MgxZn1-xO：Al的基本特性、制备方法及研究进展。     

共沉淀法制备的Cu掺杂ZnO体系的磁性

利用共沉淀法制备了Cu掺杂的Zn1-xCuxO(x=0,0.01,0.02)系列样品.利用X射线衍射仪(XRD)分析了样品的相成分,结果显示600℃烧结、掺杂浓度为1%的样品为单相纤锌矿结构,掺杂浓度为2%的样品出现第二相CuO.利用综合物性测试仪(PPMS)测量了样品的室温(300K)及低温(10K)磁性能,结果表明所有样品均呈室温铁磁性,掺杂浓度为1%、600℃烧结样品磁转变温度高于300K.最后简要讨论了铁磁性起因.     

稀土掺杂ZnO纳米颗粒的性质和应用

ZnO纳米颗粒是一种绿色环保、合成成本低的材料,广泛应用于发光以及光催化领域。稀土元素具有独特的性质,通过稀土元素掺杂ZnO,可以得到具有优良特性的发光材料和光催化剂,同时在传感以及抗菌方面也有巨大的潜力。文章介绍了稀土元素及ZnO的特性,总结了稀土掺杂ZnO纳米颗粒在光致发光、光催化等方面的原理及应用,为稀土掺杂ZnO材料的进一步发展提供参考。     

高温固相法合成Li0.98M0.02Fe0.95V0.05PO4/C的电化学性能

通过高温固相法合成锂离子电池正极材料Li0.98M0.02Fe0.95V0.05PO4/C(M=Mg、Ti、Al、Ni、Zr、Mo和Mn),用XRD、循环伏安(CV)、电化学阻抗谱(EIS)和恒流充放电等方法研究了产物的性能.金属掺杂后的材料,首次充放电比容量均高于未掺杂的纯相材料.在室温下,掺杂Mg的材料在4.2～2.4 V充放电,0.1C首次放电比容量可达154.1 mAh/g,且高倍率充放电比容量高于纯相材料,循环性能稳定,具有较好的电化学性能.     

MnBi永磁合金研究进展

Mn Bi合金具有显著的铁磁性及磁光效应,可用作永磁和磁光存储材料。Mn Bi磁性合金具有高的室温单轴磁各向异性和反常的正的矫顽力温度系数,有希望成为高温应用(~200℃)磁性材料而引起了广泛关注。但由于其相转变的复杂性,制备高纯度、高磁性能的Mn Bi合金仍存在一定的难度。近年来许多研究者对Mn Bi磁性合金的热处理工艺、制备工艺以及复合磁体等方面进行了一系列的研究。截至目前,已经基本可以批量化生产高纯高性能Mn Bi磁粉,同时所制备Mn Bi单相合金的最大磁能积(BH)max已经达到了8.4 MGOe,所制备Mn Bi复合磁体的最大磁能积(BH)max也达到了最高的18 MGOe。这些研究极大地促进了Mn Bi磁体的发展,为Mn Bi永磁体的工业化生产应用奠定了基础。本文综述了近年来高性能Mn Bi永磁材料的研究进展。     

氧化锡压敏电阻特性分析

SnO2压敏陶瓷是一种新型压敏电阻材料,具有良好的非线性特性.传统的ZnO压敏陶受微观结构的限制,其温度稳定性和老化问题仍有待改善.为此,综合比较了SnO2压敏陶瓷和传统ZnO压敏陶瓷的微观结构、热力学性质和电气性能.结果表明,相比ZnO压敏陶瓷,SnO2压敏陶瓷具有掺杂最少,由氧化物挥发导致的掺杂损失小,以及热导率高...     

Stabilization of Ferromagnetism in Co Codoped ZnO:N

First principle calculations were performed to study room temperature ferromagnetism in N doped ZnO (ZnO:N) using spin density functional theory. Substitution of O by N in ZnO results in spin polarized state exhibiting half metallic ferromagnetic characteristics. Each N dopant introduces magnetic moment of 1.0 μ_B/supercell, which is from 2p electrons of N but the magnetization energy (ΔE = 14.42 meV) is too small to stabilize ferromagnetism at room temperature. Cobalt (Co) co-doping in ZnO:N is found to enhance ferromagnetism (magnetic moment = 4.24 μ_B/supercell) with enhanced stability (ΔE = 635 meV) and is driven by hybridization between N 2p and Co 3d states.     

Unconventional magnetism in ZnO nanorods

ABSTRACT

We report room temperature ferromagnetism in vacuum annealed ZnO nanorods. ZnO nanorods were annealed at 600°C for 6 hours in an annealing chamber with a pressure of 10^?6 Torr. Our study indicates that ZnO nanorods develop room temperature ferromagnetism due to the presence of oxygen vacancy defects in it. Presence of large surface area of nanorods and oxygen vacancy are mainly responsible for the observed magnetic behavior.     

Hydrogenation induced transformation of paramagnetism to room-temperature ferromagnetism in co-doped TiO2 ceramics

Effects of Co _x Ti _1−x O _2−δ on the sinterability and the ferromagnetism properties of Co ₂sO ₃/TiO ₂ (0.0 < x < 0.06) ceramics are investigated in this paper. It is found that the Co-doped Ti O ₂ ceramics transform from paramagnetism to room-temperature ferromagnetism (RTFM) after hydrogenation. With annealing temperatures at 600^∘ C and 1000^∘ C, these as-prepared samples present anatase and rutile structures respectively, which are analyzed with X-ray diffraction (XRD). After hydrogenation, the relation between temperature variations and the magnetic susceptibility for the hydrogenated samples were measured under zero-field-cooled and field-cooled conditions by using SQUID magnetometer. And the hysteresis loops are observed. These ferromagnetism resonance data suggest that the observed RTFM is at least partly due to the Cobalt nano-particles in our hydrogenated samples.     

基于ZnO/Graphene纳米复合材料紫外光探测器的制备与实现

利用化学气相沉积法制备氧化锌（ZnO）纳米线,通过微加工工艺获得了基于 ZnO 纳米线与ZnO石墨烯量子点纳米复合材料的紫外光探测器。ZnO 石墨烯纳米复合材料的结构和表面形貌通过 X 射线电子衍射和扫描电镜来表征,结果表明,ZnO 纳米线的直径约为33 nm,与石墨烯量子点很好地复合在了一起。利用紫外可见吸收谱对样品的光吸收进行了记录,实验表明,基于ZnO复合石墨烯量子点纳米复合材料的紫外探测器在 UV 照射下显示出良好的光响应行为,该类型基于ZnO复合石墨烯量子点探测器可能在ZnO紫外探测的应用方面具有潜在的意义。     

旋转式室温磁制冷机用高场强永磁磁路的设计

把基于磁热效应的室温磁制冷技术应用到空调及家用冰箱上,除了需要具有巨磁热效应的磁致冷材料(磁工质)外,高场强永磁磁路的设计与制造也是其关键.传统方法设计的永磁磁路很难得到较高的场强.本文在中空圆柱型磁场源(hollow cylindrical flux source)的基础上,通过改进磁路结构设计出了用于旋转式室温磁制冷机的高场强永磁磁路,用有限元法计算了磁场分布,磁路工作气隙中心的场强达1.96T.     

Mn对FeCuSiBNb纳米晶合金的高频磁特性和微观结构的影响

通过差示扫描量热仪（DSC）、X射线衍射仪（XRD）、透射电子显微镜（TEM）、磁光克尔显微镜（MOKE）、直流B-H仪和阻抗分析仪等手段研究了Mn元素对FeCuSiBNb合金的热稳定性、高频磁性能、微观结构和磁畴的影响。结果表明：Mn元素对合金的第一与第二晶化温度区间和矫顽力的影响非常小,但可提高合金的高频磁导率和适用退火温度区间。与无Mn合金相比,Mn掺杂合金在10 kHz下磁导率可提高36.5%,且可抑制Fe₃B相的析出。这种良好的高频特性可归因于Mn元素的掺杂降低了纳米晶合金的平均晶粒尺寸,改善了磁畴结构的均匀度,从而降低了钉扎场。     

Prospective method of lightning protection schemes in distribution system

Grounding wires and enclosed ZnO elements have been incorporated generally in 6.6‐kV distribution systems by TEPCO for the reduction of lightning overvoltages. At present, the reliability to lightning surges is tolerably good. However, the facility of grounding wires is not inexpensive and its maintenance is hard due to corrosion and disconnection in some areas. A typical model simulating TEPCO field adopting enclosed ZnO elements has been developed and we have evaluated relative failure risks systematically according to conditions with and without grounding wires against lightning overvoltages. Two kinds of failures discussed in the paper are the flashover of insulation and the overduty of ZnO elements, and two kinds of induced and direct lightning overvoltages are studied in flashover. The greatest problem with no grounding wire is the increase of ZnO elements' duty, but it was demonstrated that a short partial grounding wire around ZnO elements or the selection of heavier ZnO elements provides a solution. The main objectives of this study are to clarify the relative failure risks systematically according to realistic field conditions, the risk of small stroke currents having long duration to ZnO elements' duty, and countermeasures against ZnO elements' overduty. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 1–10, 1999     

Electrical parameter statistic analysis and parallel coordination of ZnO varistors in low-voltage protection devices

Analyzing the nonuniformity of electrical parameters of ZnO varistors is useful to select and coordinate the ZnO varistors in parallel operation and improve the protection capability of surge-protection device (SPD). The nonuniformity of 1-mA dc voltage and impulse residual voltage of commercial low-voltage ZnO varistors were estimated by statistic analysis in this paper. The Minimum Gobble Distribution was used to describe the distribution of 1-mA dc voltage and impulse residual voltage, ZnO varistors were verified conforming to the Minimum Gobble Distribution by the Kolmogorov-Smirnov test. The relationship between the impulse residual voltage and 1-mA dc voltage has a chaos phenomenon, and they have a close relative degree by t-test, the impulse residual voltage can be estimated by voltage ratio and 1-mA dc voltage. The nonuniform phenomena of electrical parameters of ZnO varistors were simulated by Voronoi network. The current overload of ZnO varistor with reduced residual voltage is serious, in order to keep safe operation of SPDs, when we design a SPD with ZnO varistors in parallel, a safe margin coefficient of discharge withstand current should be considered according to the actual relative standard deviation of surge residual voltages of used ZnO varistors.     

用低压元件设计10000A冲击电流发生器

More and more applications of ZnO arrester in electrical system experienced more problems.One thing,that is still under some investigation,is the effect of multiple lightning strike to the performance of ZnO arrester.As we know,the design of ZnO arrester for transmission system and for distribution system differs in the point of view of the number of ZnO blocks.Transmission system,due to its higher nominal voltage than distribution system,has more numbers of ZnO blocks inside an arrester tube.In term of the current rating of an arrester,it is found that there is some different value of the current rating.The current rating of an arrester installed closer to electrical substation is higher than that of some further away from the substation.To the respond of a lightning impulse strike,the arrester will let a high value of impulse current flowing.It tends to heat the ZnO material of the arrester.If the number of impulse strike is quite high then it may give the effect to the change of the arrester performance.This condition will endanger the equipment that is protected by the arrester from lightning strikes.During this research,the scope of work is limited to making an impulse current generator toward to one having 8/20 μs wave-shape.This kind of impulse current wave-shape is the one that is used for studying the performance of ZnO block.The effect of the inductance and capacitance of the impulse current generator were also studied.A 10 fused cut out was blown by an impulse having 10321 A of 17.8/37.8 μs.A ZnO arrester block brokendown/allowed large value of current :10982 A flowing under the voltage of 10.5 kV