Die Phasen Nb3Ga2, Ta5Ga3 und Ta5Al3Bx

Zusammenfassung Die Phasen Nb₃Ga₂, Ta₅Ga₃ und Ta₅Al₃B_x werden aus den Komponenten hergestellt. Nb₃Ga₂ kristallisiert im U₃Si₂-Typ, Ta₅Ga₃ hat Cr₅Br₃-Struktur (T 2) und Ta₅Al₃B_x ist mit Mn₅Si₃ (teilweise aufgefüllt) isotyp.     

含锡AB5型非化学计量贮氢合金Ⅰ.合金的结构

采用Ｘ射线衍射法研究了ＬａＮｉ５．１５,Ｌａ（ＮｉＳｎ）５．１４,Ｌａ（ＮｉＳｎＣｏ）５．１２,Ｌａ（ＮｉＳｎＭｎ）５．１２,ＬＡ（ＮｉＳｎＣｏＭｎＡｌ）５．１０５种ＡＢ５型非化学计量贮氢合金的结构。发现主物相中并未产生第二物相,ＡＢ５型贮氢合金中Ｂ原子数发生正偏移时,晶胺体积减小,当Ｂ侧含有取代元素时,这种变化更加明显。对于非化学计量贮氢合金而言,少量Ｓｎ取代Ｎｉ后,晶胞体积大大提高。Ｍｎ,Ｃｏ     

Crystallization of Nb3Sn by arc casting

Nb-Sn mixtures were cast in an arc furnace and the formation of Nb₃Sn was investigated with respect to the starting composition. It was found that the Nb₃Sn phase was produced in four forms: (i) as a filler between interdendrites of α-Nb, (ii) as dendrites, (iii) as polycrystals (grains) and (iv) as a mass (probably an aggregation of small dendrites). The lattice parameters of Nb₃Sn were determined using the Debye-Scherrer method.     

Formation of rutile-type Nb0.94O2 by shock reduction of Nb2O5

Shock-recovery experiments on Nb₂O₅ powder specimens are made in pressure ranges up to 50 GPa using the gun method. “NbO₂” with the rutile structure is formed above about 40 GPa when an open recovery fixture is used. The tetragonal unit cell dimensions are measured to be a = 4.784(2) Å, c = 3.029(2) Å, and V = 69.34(6) ų. The metal-to-oxygen ratio is determined to be Nb_0.94O₂ by means of thermogravimetry. A comparative study is made on the shock reduction behavior of Nb₂O₅ and Ta₂O₅.     

含锡AB_5型非化学计量贮氢合金Ⅰ.合金的结构

采用X射线衍射法研究了LaNi5 .1 5 ,La(NiSn) 5 .1 4 ,La(NiSnCo) 5 .1 2 ,La(NiSnMn) 5 .1 2 ,La(NiSnCoMnAl) 5 .1 0 5种AB5 型非化学计量贮氢合金的结构。发现主物相中并未产生第二物相 ,AB5 型贮氢合金中B原子数发生正偏移时 ,晶胞体积减小 ,当B侧含有取代元素时 ,这种变化更加明显。对于非化学计量贮氢合金而言 ,少量Sn取代Ni后 ,晶胞体积大大提高。Mn ,Co和Al的加入也会影响晶胞常数。Sn ,Co ,Mn ,Al均会降低贮氢合金放氢平台压力。     

Commensurate Nb2Zr5O15: Accessible Within the Field Nb2ZrxO2x+5 After All

Doped niobium zirconium oxides are applied in field-effect transistors and as special-purpose coatings. Whereas their material properties are sufficiently known, their crystal structures remain widely uncharacterized. Herein, we report on the comparably mild sol-gel synthesis of Nb₂Zr₅O₁₅ and the elucidation of its commensurately modulated structure via neutron diffraction. We describe the structure using the most appropriate superspace as well as the convenient supercell approach. It is part of an α-PbO₂-homeotypic field with the formula Nb₂Zr_xO_2x+5, which has previously been reported only for x≥5.1, and is closely related to the structure of Hf₃Ta₂O₁₁. The results, supported by X-ray diffraction and additional synthesis experiments, are contextualized within the existing literature. Via the sol-gel route, metastable Nb−Zr−O compounds and their heavier congeners are accessible that shed light on possible structures of these commercially utilized materials.     

两步水热法合成Sn_2Nb_2O_7纳米晶及其高效可见光分解水制氢性能（英文）

铌基半导体光催化材料因其具有独特的晶体结构和能带结构在光催化分解水制氢领域受到科研工作者的高度关注.然而,大多数铌基半导体光催化剂仅能够在紫外光驱动下实现光催化分解水制氢,具有可见光响应的铌基半导体光催化剂不仅数量少而且活性较低,因此发展新型纳米铌基半导体光催化剂并实现其高效可见光催化分解水产氢具有重要的学术和实用意义.具有烧绿石构型的Sn_2Nb_2O_7材料由于具有较窄的禁带宽度(2.4 e V)和合适的导带和价带电势在可见光催化分解水制氢方面引起了科研人员广泛的兴趣.然而,目前报道的利用高温固相法制备的块体Sn_2Nb_2O_7材料由于颗粒尺寸较大和比表面积较小而导致光催化活性较差.因此,发展一种简便高效的制备方法实现纳米Sn_2Nb_2O_7材料的可控制备进而提高其可见光催化活性仍具有一定的挑战性.我们发展了一种简便的两步水热合成方法实现了Sn_2Nb_2O_7纳米晶的可控制备.扫描电镜和透射电镜测试结果表明,通过两步水热法得到的Sn_2Nb_2O_7纳米颗粒具有较好分散度,其平均颗粒尺寸为20 nm.X射线衍射测试结果也进一步证明,通过两步水热法可以实现Sn_2Nb_2O_7纳米晶的可控制备.比表面积测试结果表明,Sn_2Nb_2O_7纳米晶的比表面积约为52.2 m~2/g,远远大于固相法制备的块体Sn_2Nb_2O_7材料(2.3 m~2/g).大量研究表明,大的比表面积有利于半导体催化材料催化活性的提升.通过考查所制备的Sn_2Nb_2O_7纳米晶的可见光分解水制氢能力,对其催化性能进行了评价.研究结果表明,以乳酸为空穴消耗剂,负载0.3wt.%Pt纳米颗粒作为助催化剂的Sn_2Nb_2O_7纳米晶表现出优异的可见光催化分解水产氢性能,其产氢速率是块体Sn_2Nb_2O_7材料的5.5倍.Sn_2Nb_2O_7纳米晶可见光催化分解水产氢性能提高的主要原因是其具有高分散度的纳米颗粒、较大的比表面积和更正的价带电势.首先,颗粒尺寸的纳米化能够显著减小光生电子和空穴的迁移距离,实现光生载流子快速迁移到催化剂表面进而参与催化反应;其次,大的比表面积能够提供更多的催化活性位点,进而有利于催化活性的提高;最后,X射线光电子能谱测试表明,Sn_2Nb_2O_7纳米晶具有更正的价带电势,研究表明,价带电势越正,其光生空穴氧化能力越强.在光催化分解水制氢过程中,具有较强氧化能力的光生空穴通过与空穴牺牲剂乳酸快速反应而被消耗掉,抑制了光生电子与空穴的复合,进而导致其具有较高的光催化产氢活性.     

Photoelectrochemical Properties of Sol-Gel Nb2O5 Films

Structural, optical, electro and photoelectrochemical properties of amorphous and crystalline sol-gel Nb₂O₅ coatings have been determined. The coatings are n-type semiconductor with indirect allowed transition and present an overall low quantum efficiency ( < 4%) for UV light to electric conversion. The photoconducting behavior of the coatings is discussed within the framework of the Gärtner and Södergren models. Improvement can be foreseen if Nb₂O₅ coatings can be made of 10–20 nm size nanoparticles.     

ChemInform Abstract: Li4Ge2B as a New Derivative of the Mo2B5 and Li5Sn2 Structure Types.

Single crystals of Li₄Ge₂B are obtained by solid state reaction of stoichiometric mixtures of the elements (sealed Ta crucible, 1473 K, 15 min; rapid cooling to 25 °C).     

The Crystal Structure of Ni21Sn2P6

During an investigation of the phase equilibria in the ternary system Ni/P/Sn, the existence of a new phase Ni₂₁Sn₂P₆ with a composition close to the known Ni₁₀P₃Sn phase was found. The crystal structure of the new phase was determined using single crystal X‐ray diffraction. The structure was solved employing Patterson and Difference Fourier Analysis. Ni₂₁P₆Sn₂ (space group , a = 1112.2 pm) crystallizes in an ordered variant of the C₆Cr₂₃ structure common to many carbides, borides and phosphides. The relation between Ni₂₁Sn₂P₆ and other C₆Cr₂₃ type phases and to Ni₁₀P₃Sn was established.     

Synthesis, Crystal Structure and Band Structure of Eu3Sn5 with Arachno-type Zintl Anions

A new polar intermetallic compound, Eu3Sn5, has been synthesized by solid-state reaction of the corresponding pure elements in a stoichiometric ratio in a welded tantalum tube at high temperature. Its crystal structure was established by single-crystal X-ray diffraction. Eu3Sn5 crystallizes in orthorhombic, space group Cmcm with a = 10.466(11), b = 8.445(8), c = 10.662(12) , V = 942.4(17) 3, Z = 4, Mr = 1049.33, Dc = 7.396 g/cm3, μ = 32.578 mm-1, F(000) = 1756, the final R = 0.0236 and wR = 0.0472 for 535 observed reflections with I > 2σ(I). Its structure belongs to the modified Pu3Pd5 type. It is isostructural with Sr3Sn5 and Ba3Sn5, featuring [Sn5] square pyramidal clusters described as "arachno" according to the Wade-Mingos electron counting rules. The europium cations are located at the voids between the square pyramidal clusters. Results of the extended Hückel band structure calculations indicate that Eu3Sn5 is metallic.