Superconductivities and structural properties of ternary Tiben Zrben Ta alloys

Superconductivities and structural properties of Ti-Zr-Ta ternary alloys are extensively investigated. The TiZrTa sample has a cubic structure (β -phase) and shows a sharp superconducting transition at a critical temperature (T_c) of about 7.3 K. In addition, two series of Ti-Zr-Ta alloys, with nominal compositions of Ti_65-xZr₃₅Ta_x and Ti_xZr_65-xTa₃₅ respectively, are prepared, and their superconductivities and crystal structures change regularly with the chemical composition. Our experimental study also indicates that the annealing processing of this kind of material can cause the transition temperature to increase and the highest T_c is observed to be about 8.3 K in annealed samples.     

Mn、Ti掺杂对NaxCoO2体系超导电性和电荷有序化影响

本文研究了Mn、Ti掺杂对Na0.3Co1-xMxO2·1.3H2O超导电性和 Na0.5Co1-xMxO2材料电荷有序现象的影响.我们成功合成了Na0.7Co1-xMxO2(M= Mn和Ti,0≤x≤0.1)系列样品,并采用不同强度氧化剂氧化脱钠,分别获得Na0.5Co1-xMxO2和水合物Na0.3Co1-xMxO2·1.3H2O (0≤x≤0.1, M= Mn和Ti).X射线衍射分析表明所有样品都是比较好的单相,它们的晶格常数随着Ti和Mn的含量发生系列变化.物性检测显示Na0.3Co1-xMxO2·1.3H2O的超导电性随着Mn和Ti掺杂量的增加明显减弱,在Mn掺杂为x=0.02 或Ti掺杂为x=0.01时其超导电性消失;磁性检测发现随着掺杂量的增加,Na0.5Co1-xMxO2电荷有序态被逐渐破坏,其中掺Mn比掺Ti对电荷有序化行为的影响更为明显.     

Capturing the non-equilibrium state in light–matter–free-electron interactions through ultrafast transmission electron microscopy

Ultrafast transmission electron microscope(UTEM) with the multimodality of time-resolved diffraction, imaging,and spectroscopy provides a unique platform to reveal the fundamental features associated with the interaction between free electrons and matter. In this review, we summarize the principles, instrumentation, and recent developments of the UTEM and its applications in capturing dynamic processes and non-equilibrium transient states. The combination of the transmission electron microscope ...     

铁基超导体的微结构和结构相变研究

铁基超导体表现出丰富的结构和物理性质,在多个典型体系中存在着结构相变和多重有序态之间的关联与竞争.例如,母相化合物LaFeAsO在150K附近发生从四方相（P4/nmm）到正交相（Cmma）的结构相变,同时其电输运性质和磁化率也表现出明显的反常行为.微结构分析发现,在CaFe2As2样品中,存在准周期调制结构,而且在低温区,122体系存在丰富的孪晶畴结构,这种孪晶结构是结构相变的直接结果.另外,在超导材料KxFe2-ySe2（0.7≤x≤0.8,0.2≤y≤0.4）中,Fe空位有序态和结构相分离是理解其结构,也是理解其磁性和输运性质的关键问题,特别是沿[130]晶体带轴方向的5倍超结构与系统的超导电性存在密切关系.     

CuCl2-FeCl3-H2SO4石墨插层化合物的结构特征

"采用水热法在150 ℃合成出了CuCl2-FeCl3-H2SO4的石墨插层化合物．通过X射线衍射、EDX、高分辨透射电子显微术分析了该石墨插层化合物的结构和成分．分析表明,CuCl2-FeCl3-H2SO4已经成功地插入到石墨的片层之间．测量了从5 K到300 K的磁化率随温度变化曲线,发现在低温时,该石墨插层化合物存在两个反铁磁转变,转变温度分别为50和100 K．"     

Ultrafast electron microscopy in material science

Recent advances in the ultrafast transmission electron microscope(UTEM), with combined spatial and temporal resolutions, have made it possible to directly visualize the atomic, electronic, and magnetic structural dynamics of materials.In this review, we highlight the recent progress of UTEM techniques and their applications to a variety of material systems.It is emphasized that numerous significant ultrafast dynamic issues in material science can be solved by the integration of the pump–probe approach with the well-developed conventional transmission electron microscopy(TEM) techniques. For instance, UTEM diffraction experiments can be performed to investigate photoinduced atomic-scale dynamics, including the chemical reactions, non-equilibrium phase transition/melting, and lattice phonon coupling. UTEM imaging methods are invaluable for studying, in real space, the elementary processes of structural and morphological changes, as well as magnetic-domain evolution in the Lorentz TEM mode, at a high magnification. UTEM electron energy-loss spectroscopic techniques allow the examination of the ultrafast valence states and electronic structure dynamics, while photoinduced near-field electron microscopy extends the capability of the UTEM to the regime of electromagnetic-field imaging with a high real space resolution.     

水热法制备蒲公英状微晶和纳米带状β-SrV2O6及微结构表征

"利用Sr(NO3)2和V2O5作为反应前驱物, 已二酸作为矿化剂,在水热法反应条件下成功制备了微米尺寸蒲公英状及纳米尺寸的纳米带状β-SrV2O6晶微体. 通过粉末X衍射和电子显微镜的研究分析,结果表明所得的反应生成物属于正交晶系,其晶格常数为a=9.694 ?,b=3.687 ?,c=12.570 ? (空间群Pnma). 电子显微结果表明蒲公英状的微晶是揭示许多棒状微晶呈球型放射状构成的图案,而纳米带状的β-SrV2O6则呈现显示良好的挠性. 两者的微晶体生长方向沿h010i晶轴方向. 详细探讨了水     

电子铁电体研究进展

电子铁电性是基于关联体系电荷有序态的一种新的物理现象。近期研究发现,这种新型铁电体通常表现出丰富的磁电性质和耦合效应,在发展可控性多功能微电子器件方面具有广阔的应用前景。本文重点介绍了电子型铁电体代表材料LuFe2O4的实验和理论研究进展,着重探讨了电荷序相变,极化机理,介电,铁电,磁电耦合等重要物理性能。随后,简要介绍了其它体系在相关问题研究中的进展情况,包括：钙钛矿体系Pr(Ca)MnO3,Fe3O4和有机材料(TMTTF)2X等。     

Two-coupled structural modulations in charge-density-wave state of SrPt_2As_2 superconductor

Transmission electron microscopy(TEM) study of SrPt2As2 reveals two incommensurate modulations appearing in the charge-density-wave(CDW) state below TCDW≈ 470 K. These two structural modulations can be well explained in terms of condensations of two-coupled phonon modes with wave vectors of q1= 0.62a*on the a*–b*plane and q2=0.23a*on the a*–c*plane. The atomic displacements occur along the b-axis direction for q1and along the c-axis direction for q2, respectively. Moreover, the correlation between q1and q2can be generally written as q1=(q2+ a*)/2 in the CDW state, suggesting the presence of essential coupling between q1and q2. A small fraction of Ir doping on the Pt site in Sr(Pt1-xIrx)2As2(x ≤ 0.06) could moderately change these CDW modulations and also affect their superconductivities.