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La2/3Ca1/3MnO3中绝缘体-金属的转变:小极化子的退局域 总被引:2,自引:2,他引:0
通过电阻率、磁化曲线和电子自旋共振谱(ESR)的测量,对超大磁阻材料La2,3Ca1/3MnO3的绝缘体.金属(I-M)转变过程进行了研究。在磁场作用下,高温顺磁相的电阻率与绝热小极化子跃迁模式[ρ~BTexp(En/kT)]相吻合,低温铁磁相的电阻率与单磁振子散射模式(p-ρ0 AT^2)相吻合,这意味着在I-M转变期间,小极化子和巡游载流子是共存的。基于磁有序过程引发小极化子退局域这一认识,用两相模型定量描述I-M转变期间的输运行为,在不同磁场下电阻率的计算结果与实验数据非常接近,有力证明了I-M转变是由于小极化子退局域和两种特殊的输运行为共存。 相似文献
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《稀有金属》2015,(6)
用固相反应法制备二相复合体La2/3Ca1/3Mn O3/x Cu O(x=0,0.04,0.08,0.12,0.20,0.30)。用X射线衍射(XRD)图谱、扫描电子显微镜(SEM)照片检测样品的结构,通过零场冷和加场冷的电阻率-温度(ρ-T)曲线、磁电阻-温度(MR-T)曲线研究界面效应对电输运性质及磁电阻的影响。结果表明:样品形成完好的钙钛矿相和Cu O相;复合样品的颗粒比较均匀,颗粒大小约2μm,界面比较清晰;复合样品的ρ-T曲线出现双峰,x=0.04的样品电输运性质出现反常,它的电阻率既小于x=0的电阻率,也小于x=0.08的电阻率;复合样品的MR-T曲线也出现双峰,x=0.20,0.30的样品,0.8 T磁场下在50~250 K温区磁电阻不小于13.4%,实现了大温区且有较高磁电阻,有利于MR的实际应用。用影响电输运的多种因素的竞争很好地解释了界面效应。 相似文献
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为解决氧化铁红在高温下呈现不稳定性的问题, 采用非均匀成核法使Si(OH)4和Al(OH)3均匀包覆在氧化铁红粉末颗粒表面, 用X射线衍射仪、透射电镜、 Zeta电位测定仪对包覆前后的Fe2O3粉末颗粒进行分析. 结果表明, 通过非均匀成核法可以制备出被SiO2和Al2O3包覆的Fe2O3复合粒子, 其技术的关键是如何控制反应溶液pH值和涂层物质沉淀的反应浓度, 以保持被覆颗粒稳定的悬浮特性. 相似文献
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介绍了新型超导体MgB2的基本超导电性,综述了MgB2材(多晶)、线材和带材的主要制备技术,并对MgB2超导材料的应用前景进行了展望. 相似文献
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Alfred Seeger 《Metallurgical and Materials Transactions B》1970,1(11):2987-2996
After a brief summary of the historical development of the field of superconductivity and the background required for the topics treated in the present paper, some of the relationships between superconductivity and physical metallurgy are discussed. These are mainly in two areas: i) The distribution of magnetic flux in super conductors may show fine structures (boundaries between normal and superconducting regions in the intermediate state of type-I superconductors; quantized flux-lines in the Shubnikov phase of type-II superconductors) on such a scale that they interact strongly with the metallurgical microstructure of the superconducting materials, such as grain boundaries, dislocations, precipitates, and so forth. ii) Ideally, the flux-lines in a type-II superconductor form a two-dimensional lattice (Abrikosov lattice). The decoration technique of Träuble and Essmann has permitted the direct observation of these flux-lines lattices and has revealed that they contain a rather high density of defects. Most of them are known from the studies of defects in crystals, such as grain boundaries, dislocations, stacking faults, and vacancy and interstitial lines, but also disclinations, which were predicted by theory but have not yet been observed in metals, were investigated. 相似文献
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在研制稀土AlMg3W合金的基础上.采用金相观察、X射线衍射等手段,并通过力学性能、耐磨性能、焊接性能、热膨胀性能等对比测试,系统地分析了稀土对AlMg3W合金显微结构及物理性能的影响。结果表明,当稀土含量为0.05%时,稀土AlMg3W合金的性能最佳。 相似文献
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红外探测材料的发展状况及未来发展 总被引:2,自引:1,他引:1
红外探测仪中,半导体红外探测技术相对较为成熟,逐步由传统半导体材料向半导体异质结、半导体超品格、半导体量子阱和半导体量子点等材料发展;人们发现超导的特性之后,设法研究超导红外探测仪,超导红外探测仪中又分STS、热电子和超导薄膜等类型;近些年又发展了超巨磁阻红外探测仪。技术的发展使材料的灵敏度、工作温度和探测率也在不断的向高层次发展,并不断的发现新的材料。在规模上,红外探测仪将会不断的向大规模焦平面方向发展(即热成像仪);探测波长方面,要由单色向双色和多色发展;随技术的发展,红外探测仪应用也将大大的拓展。 相似文献
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Wang Zhenling Qiao Ziwen Quan Zewei Lin Jun 《中国稀土学报(英文版)》2006,24(3):263-263
Eu^3+-doped LaPO4 nanoparticles were prepared by polyol method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), thermogravimetry-differential thermal analysis (TG-DTA), Uv-vis diffuse reflectance spectra (DRS), photoluminescence (PL) spectra and lifetime measurement. The results of XRD indicate that the as-prepared nanoparticles are crystallized well at 160 ℃ and assigned to the monoclinic monazite-structure of LaPO4 phase. The obtained LaPO4:Eu^3+ nanoparticles are spherical with narrow size distribution and the average size of 25 nm. 相似文献
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Series of doped rare earth complexes-EuxGd(1-x)(CA)3·nH2O (CA=citric acid) were synthesized. Some characterizations were taken for these complexes. The experimental results shows that the doped rare earth complexes have the best fluorescence property when the ratio of Eu and Gd is from 0.7 to 0.3. Silicon rubber-based composites were prepared by mechanical blending the EuxGd(1-x)(CA)3·nH2O and silicon rubber. Then, the fluorescent property of the composites was studied. It is found that the fluorescence intensity of the composites increase linearly with the contents of the rare earth complexes increasing. 相似文献