The Josephson effect in superconductors with heavy Fermions

The Josephson effect between a usual superconductor with even-parity pairing and a heavy-Fermion superconductor with odd-parity pairing would not be zero. Instead, due to spin-orbit coupling it would be of relative magnitude a/Ξ_o compared to the effect between two even-parity superconductors. a/Ξ_o, the ratio of lattice constant to pair size, is comparable to 0.1 for heavy-Fermion superconductors. Recent claims, that with strong spin-orbit coupling the even-parity to odd-parity Josephson effect should be of order unity times the even-even effect, are shown to be incorrect.     

Mictomagnetic behaviour in MnAlC(Ni) alloys

The as cast, thermally treated and hot extruded Mn_1.058Al_0.909C_0.022Ni_0.011 samples were investigated by X-rays, neutron diffraction and magnetic measurements. The hot extruded magnets produced by Matsushita Electric Ind. Co., having (BH)_max = 5 MGOe, show a mictomagnetic-type behaviour.     

Competition between addition and redox processes in reactions of Nitroarenes with Lithium-dithianes

The reaction of 2-lithio-1,3-dithianes with nitroarenes gives 2-(or 4-)[(1,3-dithian)-2'-y1]cyclohexa-3,5(or 2,5-)-diene-1-nitronate compounds (conjugate-addition products), free nitroarene radical anions (redox products), 1,3-dithianes and 2,2'-bis-(1,3-dithianes). The conjugate -addition and redox products were converted in the respective nitroaromatic compounds by oxidation in situ with O₂ or DDQ. The ratio between addition and redox products increases with decrease of temperature. 2-H-2-Lithio-1,3-dithiane can give both 1,4- and 1,6-addition products, while 2-methyl- and 2-phenyl derivatives give only 1,6-addition products. A mechanism involving an s.e.t. from lithium dithianes to nitroarenes followed by various decay routes is suggested for the two radical species.     

纳米氧化镱对熔融石英析晶动力学机制的影响

本文研究引入纳米氧化镱对熔融石英析晶机制及动力学过程的影响.通过X射线衍射仪(XRD)测试结果分析了纳米氧化镱的引入对熔融石英陶瓷析晶率的影响,采用动力学方法分析了纳米氧化镱的引入对熔融石英陶瓷析晶机制的影响,同时探讨了其等温析晶动力学过程.研究表明,熔融石英陶瓷的晶粒向二维兼有一维及三维的方式生长,引入纳米氧化镱的熔...     

The molecular structures of bis(pentamethylcyclopentadienyl)-calcium and -ytterbium in the gas phase; two bent metallocenes

Gas electron diffraction studies show that whereas the ligand rings in (η⁵-C₅Me₅)₂Mg, are essentially parallel, the thermal average structures of (η⁵-C₅Me₅)₂Ca and (η⁵-C₅Me₅)₂Yb are bent, the ring-centroid—metal—ring-centroid angles being 154(3)° and 158(4)°, respectively.     

Darstellung von arylhalogenboranen

In a ligand-exchange reaction between aryltrimethylsilanes, (ArSiMe₃) and halogenboranes, (BX₃ or ArBX₂), arylhalogenboranes (ArBX₂, ArAr'BX or Ar₂BX) and halogentrimethylsilane are formed. This transfer of substituted aromatic groups from a silicon to a boron atom is an efficient synthetic pathway for the preparation of the corresponding arylhalogenboranes and diarylhalogenboranes with different aryl groups. Physical properties and spectroscopical data of the new arylhalogenboranes are given.     

Studies of phases in the KNbO3Nb2O5 system by high-resolution electron microscopy and X-ray powder diffraction

High-resolution electron microscopy and X-ray powder diffraction studies of specimens in the KNbO₃Nb₂O₅ system have shown that, besides the previously reported layer structures K₄Nb₆O₁₇ and LKNb₃O₈, there exist three different types of tetragonal tungsten-bronze-related structures as well as a block structure, KNb₁₃O₃₃, isostructural with the NaNb₁₃O₃₃ phase. The cell parameters and the structural relations to TTB are discussed. The first two TTB-related phases, superstructures of the TTB-type, are characterized by the formula K_2xNb^A_2−x(NbO)^C_xNb₁₀O₃₀, where 0 < x ≤ 2. H-KNb₃O₈ (x = 2), a high-temperature phase, exhibits a new mode of linking pentagonal columns in pairs. Various types of microstructures between the two TTB-related phases will be discussed. The third TTB-related phase can be described as K_10−5yNb^A_yNb₁₀O₃₀, where 0.8 < y < 1.25. No pentagonal columns have so far been observed. In specimens prepared at T > 1275 K, the low-temperature modification L-KNb₃O₈, transforms in the solid state via a poorly crystallized phase to TTB-related structures. Some geometrical features of the L-KNb₃O₈, KNb₁₃O₃₃ structures and the TTB phase will also be presented.     

硅锗合金Seebeck系数影响因素的研究

作为一种洁净能源,硅锗合金的热电转换性能的研究越来越受到人们的重视.本文重点研究了不同Ge浓度的硅锗合金以及Si、Ge单晶在300～1100K温度范围内,Seebeck系数随温度的变化.并对组分相同导电类型不同、晶向不同以及结晶状态不同的样品的Seebeck系数进行了比较.在研究温度区间,Seebeck系数的绝对值大小一般在200～600μV/K之间,随温度不同连续变化.通过对比发现SiGe合金的Seebeck系数大小不仅与Ge的浓度和温度有关,其他因素对其绝对值也有影响,其中晶向最为明显,表现出了明显的各向异性.此外,材料本身的电阻率除了作为一个热电参数影响最优值外,其大小还对Seebeck系数的绝对值有影响,即掺杂济浓度对Seebeck系数的影响.     

工作气压对磁控溅射ITO薄膜性能的影响

工作气压在ITO薄膜的制备过程中是一个重要的工艺参数,直接决定着薄膜的性能.本文利用射频磁控溅射方法,采用氧化铟锡陶瓷靶材,在衬底温度为175℃,工作气压范围为0.45～1.0 Pa条件下,制备了氧化铟锡透明导电薄膜.研究了工作气压对其微观结构、表面形貌和光电特性的影响.在衬底温度为175℃、纯氩气中制备的氧化铟锡薄膜电阻率为3.04 ×10-4 Ω·cm、可见光波段(400～800 nm)透过率为91.9;,适合用作异质结太阳电池的前电极和减反射膜.     

Molecular structure and fluxional behaviour of the iron-rhodium methoxymethylidyne cluster complex Fe2 Rh(μ-H)(μ3-COCH3)(CO)7(η-C5H5)

The complex Fe₂Rh(μ-H)(μ₃-COCH₃)(CO)₇(η-C₅H₅) prepared by treatment of Fe₃(μ-H)(μ-COCH₃)(CO)₁₀ with Rh(CO)₂ (η-C₅H₅), has been examined by single crystal X-ray diffraction. The compound crystallises in the monoclinic space group C2/c (No. 15) with a 25.409(2), b 8.129(1), c 17.044(1) Å, β 103.744(6)°, V 3419.6(6) ų and D_c 2.02 g cm⁻³ for Z = 8 and M = 519.8. Data were collected for 2° ⩽ θ ⩽ 30° with graphite monochromated X-radiation (Mo-K_α) using an Enraf-Nonius CAD4-F diffractometer. The structure was refined to R = 0.025 (R_itw = 0.037) for 3557 observed [I ⩾ 3(σI)], absorption corrected data. The complex contains an asymmetrically bonded methoxymethylidyne ligand capping an Fe₂Rh triangular face (Fe(1)-C(8) 1.863(3), Fe(2)-C(8) 1.881(3), Rh-C(8), 2.211(3) Å). The terminal carbonyl ligand on the rhodium atom shows slight semi-bridging interactions with the two iron atoms (Fe(1) … C(7) 2.888(4), Fe(2) … C(7), 2.769(4) Å, Rh-C(7)-O(7) 169.1(4)°. The iron—iron vector is spanned by a (directly located) μ-hydride ligand. Variable temperature ¹³C NMR studies reveal fluxional behaviour, including a temperature dependence both of the alkylidyne carbon chemical shift (δ 323.5 at +80°C, δ 319.2 at −90°C) and its ¹⁰³Rh coupling constant (¹J(Rh-C) 23 Hz at −90°C, 26 Hz at +80°C). These data suggest an increased interaction of the ‘semi-μ₃’ alkylidyne ligand with the rhodium centre at higher temperatures, primarily associated with the highest energy fluxional process. Extended Hückel MO calculations on this complex allow a rationalisation of the ‘semi-μ₃’ nature of the COCH₃ group.