Effects of combined substitution of Dy and Mo or Si on the crystal structures and magnetic properties of Nd1?yDyyFe11?xTiMx (M = Mo, Si) compounds

A series of Nd_1−y Dy _y Fe_11−x TiM_x (M = Mo, Si) alloys have been prepared by arc melting and studied by X-ray diffraction and neutron diffraction. All samples are found to crystallize in the ThMn₁₂-type structure. The lattice parameters a and c and unit cell volume V of Nd_0.5Dy_0.5Fe_11−x TiMo _x alloys increase linearly with increasing content of Mo (x), while the lattice parameters a and c and unit cell volume V of Nd_0.5Dy_0.5Fe_11−x TiSi _x alloys decrease linearly with increasing content of Si(x). In Nd _y Dy_1−y Fe_11−x TiM _x (M = Mo, Si) compounds, Ti and Mo atoms preferentially occupy the 8i sites and Si atoms preferentially occupy the 8j and 8f sites. Magnetic measurements show that the substitution of Fe by either Mo or Si leads to a decrease in the Curie temperature. Supported by the National Natural Science Foundation of China (Grant No. 20775088) and the Foundation of State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences (Grant No. KF2008-06)     

Crystallographic and electrochemical characteristics of La(0.7)Mg(0.3)Ni(5.0-x)(Al(0.5)Mo(0.5)x hydrogen-storage alloys.

The structure, hydrogen-storage property and electrochemical characteristics of La(0.7)Mg(0.3)Ni(5.0-x)(Al(0.5)Mo(0.5))x (x = 0-0.8) hydrogen-storage alloys have been studied systematically. X-ray diffraction Rietveld analysis shows that all the alloys consist of an La (La,Mg)2Ni9 phase and an LaNi5 phase. The pressure-composition isotherms indicate that the hydrogen-storage capacity first increases and then decreases with increasing x, and the equilibrium pressure decreases with increasing x. Electrochemical measurements show that the maximum discharge capacity and the exchange-current density of the alloy electrodes increase as x increases from 0 to 0.6 and then decrease when x increases further from 0.6 to 0.8. Moreover, the low-temperature dischargeability of the alloy electrodes increases monotonically with increasing x in the alloys.     

(Nd1-xYx)3Fe27.31Ti1.69化合物的结构与磁性研究

制备了(Nd1-xYx)3Fe27.31Ti1.69(0≤x≤0.6)系列化合物,通过X射线衍射和磁性测量等手段研究了它们的结构和磁性.这些化合物均为Nd3(Fe,Ti)29型结构,A2/m空间群.化合物晶胞体积随Y含量增加而单调减少,居里温度Tc随Y含量增加略有降低,说明化合物的居里温度主要由Fe-Fe之间的交换相互作用所决定.温度为5K时,饱和磁化强度Ms随Y含量的增加而单调降低,与一个简单的稀释模型预期结果一致.所得化合物在低温下均发生自旋重取向,自旋重取向温度Tsr随Y含量增加而单调降低,从x=0时的232K减小到x=0.6时的121K.基于磁晶各向异性的研究结果确定了所得化合物的自旋相图.     

MTi(0.7)Mo(0.3)Mo(5)O(10) (M = SR, Eu), first evidence of mono- and bicapped bioctahedral Mo(11) and Mo(12) clusters: synthesis, crystal structures, and physical properties

The novel quaternary reduced molybdenum oxides MTi(0.7)Mo(0.3)Mo(5)O(10) (M = Sr, Eu) have been synthesized by solid-state reaction at 1400 degrees C for 48 h in sealed molybdenum crucibles. Their crystal structures were determined on single crystals by X-ray diffraction. Both compounds crystallize in the orthorhombic space group Pbca with 8 formula units per cell and the following lattice parameters: a(Sr) = 9.1085 (7), b(Sr) = 11.418 (1), and c(Sr) = 15.092 (3) A; a(Eu) = 9.1069 (7), b(Eu) = 11.421 (2), and c(Eu) = 15.075 (1) A. The Mo network is dominated by bioctahedral Mo(10) clusters, which coexist randomly with Mo(11) and Mo(12) clusters (monocapped and bicapped Mo(10) clusters). The Mo-Mo distances within the clusters range from 2.62 to 2.92 A and the Mo-O distances from 1.99 to 2.17 A as usually observed in the reduced molybdenum oxides. The Sr(2+) and Eu(2+) ions occupy large cavities, which result from the fusion of two cubooctahedra and thus are surrounded by 11 oxygen atoms. The M-O distances range from 2.50 to 3.23 A for the Sr compound and from 2.49 to 3.24 A for the Eu analogue. Single-crystal resistivity measurements indicate that both materials are poor metals with transitions to semiconducting states below 50 and 40 K and room temperature resistivity values of 9 x 10(-3) and 5 x 10(-3) Omega.cm for the Sr and Eu compounds, respectively. The magnetic susceptibility data indicate paramagnetic behavior due to the Eu(2+) moment at high temperatures for the Eu compound and do not reveal the existence of localized moments on the Mo and Ti sublattice in the Sr compound. An XPS study clearly suggests that the isolated Ti ions are tetravalent. Theoretical considerations preclude the existence of heterometallic Mo-Ti clusters.     

Dy2（Fe1—xSix）17系列化合物内禀磁性及穆斯堡尔效应研究

详细研究了Ｄ２（Ｆ１ｘ－Ｓｉｘ）１７系列化合物的晶格结构和内禀磁性。Ｘ射线衍射分析表明，Ｄｙ２（Ｆｅ１－ｘＳｉｘ）１７系列化合物呈现Ｔｈ２Ｎｉ１７结构牙或Ｔｈ２Ｚｎ１７结构相，居里温度ＴＣ随Ｘ的增大而增大，饱和磁化强度σｓ随ｘ的增加而减小。     

Syntheses，Structures and Properties of Some New Composition Perovskite Compounds：Sr_（0．6）Bi_（0．4）FeO_（2．7），Sr_（1－x）Bi_xFeO_（3－y） and Ba_（1．5）Pt_（0．5）Mn_2O_6

Ｓｙｎｔｈｅｓｅｓ，ＳｔｒｕｃｔｕｒｅｓａｎｄＰｒｏｐｅｒｔｉｅｓｏｆＳｏｍｅ　ＮｅｗＣｏｍｐｏｓｉｔｉｏｎＰｅｒｏｖｓｋｉｔｅＣｏｍｐｏｕｎｄｓ：Ｓｒ_（０．６）Ｂｉ_（０．４）ＦｅＯ_（２．７），Ｓｒ_（１－ｘ）Ｂｉ_ｘＦｅＯ_（３－ｙ）　ａｎｄ　Ｂａ...     

Cubic aluminum silicides RE8Ru12Al49Si9(Al(x)Si12-x) (RE = Pr, Sm) from liquid aluminum. Empty (Si,Al)12 cuboctahedral clusters and assignment of the Al/Si distribution with neutron diffraction.

Two new quaternary aluminum silicides, RE8Ru12Al49Si9(Al(x)Si12-x) (x approximately 4; RE = Pr, Sm), have been synthesized from Sm (or Sm2O3), Pr, Ru, and Si in molten aluminum between 800 and 1000 degrees C in sealed fused silica tubes. Both compounds form black shiny crystals that are stable in air and NaOH. The Nd analog is also stable. The compounds crystallize in a new structural type. The structure, determined by single-crystal X-ray diffraction, is cubic, space group Pm3m with Z = 1, and has lattice parameters of a = 11.510(1) A for Sm8Ru12Al49Si9(Al(x)Si12-x) and a = 11.553(2) A for Pr8Ru12Al49Si9(Al(x)Si12-x) (x approximately 4). The structure consists of octahedral units of AlSi6, at the cell center, Si2Ru4Al8 clusters, at each face center, SiAl8 cubes, at the middle of the cell edges, and unique (Al,Si)12 cuboctohedral clusters, at the cell corners. These different structural units are connected to each other either by shared atoms, Al-Al bonds, or Al-Ru bonds. The rare earth metal atoms fill the space between various structural units. The Al/Si distribution was verified by single-crystal neutron diffraction studies conducted on Pr8Ru12Al49Si9(Al(x)Si12-x). Sm8Ru12Al49Si9(Al(x)Si12-x) and Pr8Ru12Al49Si9(Al(x)Si12-x) show ferromagnetic ordering at Tc approximately 10 and approximately 20 K, respectively. A charge of 3+ can be assigned to the rare earth atoms while the Ru atoms are diamagnetic.     

Polar symmetry and intercalation of new multilayered hybrid molybdates: [M2(pzc)2(H2O)x][Mo5O16] (M = Co, Ni)

The layered molybdate [M2(pzc)2(H2O)x][Mo5O16] (I: M = Ni, x = 5.0; II: M = Co, x = 4.0; pzc = pyrazinecarboxylate) hybrid solids were synthesized via hydrothermal reactions at 160-165 degrees C. The structures were determined by single-crystal X-ray diffraction data for I (Cc, Z = 4; a = 33.217(4) A, b = 5.6416(8) A, c = 13.982(2) A, beta = 99.407(8) degrees , and V = 2585.0(6) A3) and powder X-ray diffraction data for II (C2/c, Z = 4; a = 35.42(6) A, b = 5.697(9) A, c = 14.28(2) A, beta = 114.95(4) degrees , and V = 2614(12) A3). The polar structure of I contains new [Ni2(pzc)2(H2O)5]2+ double layers that form an asymmetric pattern of hydrogen bonds and covalent bonds to stair-stepped [Mo5O16]2- sheets, inducing a net dipole moment in the latter. In II, however, the [Co2(pzc)2(H2O)4]2+ double layers have one less coordinated water and subsequently exhibit a symmetric pattern of covalent and hydrogen bonding to the [Mo5O16]2- sheets, leading to a centrosymmetric structure. Thermogravimetric analyses and powder X-ray diffraction data reveal that I can be dehydrated and rehydrated with from 0 to 6.5 water molecules per formula unit, which is coupled with a corresponding contraction/expansion of the interlayer distances. Also, the dehydrated form of I can be intercalated by approximately 4.3 H2S molecules per formula unit, but the intercalation by pyridine or methanol is limited to less than one molecule per formula unit.     

Structurally complex cobalt intermetallics grown from liquid aluminum: Co19Al45Si(10-x) (x = 0.13) and Co5Al14Si2

The cobalt aluminum silicides Co19Al45Si(10-x) (x = 0.13) and Co5Al14Si2 were synthesized in liquid aluminum and characterized by single-crystal X-ray diffraction. Co19Al45Si(10-x) (x = 0.13) crystallizes in the monoclinic space group C2/c with lattice parameters a = 19.991(2) A, b = 19.143(2) A, c = 12.8137(15) A, beta = 123.583(2) degrees. Co5Al14Si2 adopts the orthorhombic space group Pnma with cell parameters a = 13.8948(19) A, b = 23.039(3) A, c = 7.3397(10) A. Both structures are exceptionally complex with the Co2Si2 rhombus being a common building motif. The coordination environments of cobalt atoms resemble those of the transition metals in typical quasi-crystal approximants. Co5Al14Si2 shows oxidation resistance in air up to 1000 degrees C by forming a dense-packed Al2O3 layer on the surface of the crystal.     

Salt-inclusion synthesis of two new polar solids, Ba6Mn4Si12O34Cl3 and Ba6Fe5Si11O34Cl3

A new family of salt-containing, mixed-metal silicates (CU-14), Ba6Mn4Si12O34Cl3 (1) and Ba6Fe5Si11O34Cl3 (2), was synthesized via the BaCl2 salt-inclusion reaction. These compounds crystallize in the noncentrosymmetric (NCS) space group Pmc2(1) (No. 26), adopting 1 of the 10 NCS polar, nonchiral crystal classes, mm2 (C2v). The cell dimensions are a = 6.821(1) A, b = 9.620(2) A, c = 13.172(3) A, and V = 864.4(3) A3 for 1 and a = 6.878(1) A, b = 9.664(2) A, c = 13.098(3) A, and V = 870.6(3) A3 for 2. The structures form a composite framework made of the (M(4+x)Si(12-x)O34)9- (M = Mn, x = 0; M = Fe, x = 1) covalent oxide and (Ba6Cl3)9+ ionic chloride sublattices. The covalent framework exhibits a pseudo-one-dimensional channel where the extended barium chloride lattice (Ba3Cl1.5)(infinity) resides, and it consists of fused eight-membered meta-silicate rings propagating along [100] via sharing two opposite [Si2O7]6- units to form an acentric lattice. Single-crystal structure studies also reveal the ClBa4 unit adopting an interesting seesaw configuration, in which the lone pair electrons of chlorine preferentially face the oxide anions of the transition metal silicate channel, thus forming the observed polar frameworks. Similar to the synthesis of organic-inorganic hybrid materials, the salt-inclusion method facilitates a promising approach for the directed synthesis of special framework solids, including NCS compounds, via composite lattices.     

(Gd1-xREx)5Si4(RE=Dy, Ho)系列材料磁熵变研究

对 (Gd1-xDyx)5Si4(x=0.1, 0.2, 0.3, 0.35) 和(Gd1-xHox)5Si4(x=0.05, 0.15, 0.25)系列合金的居里温度、磁相变、磁熵变等磁性质进行了研究. 结果发现 该系列合金保持了Gd5Si4的Sm5Ge4正交型晶体结构, 居里温度随着引入的x量的增加而呈近似线性减小趋势;在居里温度附近样品的磁特性符合二级相变规律;通过调节Dy 或Ho的含量调节居里点, 样品中不含贵重元素Ge, 大大降低了成本;在较宽的温度范围和低场下(＜2 T)具有较大的磁熵变值从而使其适合于被制成梯度功能复合材料. 研究表明 (Gd1-xREx)5Si4(RE=Dy, Ho)系列材料有望成为较好的室温低场磁制工质.     

Fe部分替代Cu对低钴AB_5型贮氢合金相结构和电化学性能的影响

为了获得既具有较高电化学容量又具有良好循环稳定性的低钴AB5型贮氢合金,研究了Fe部分替代Cu对低钴AB5型贮氢合金相结构和电化学性能的影响.采用真空感应熔炼方法,制备了一系列含Cu和Fe的低钴AB5型贮氢合金LaNi3.55Mn0.35Co0.20Al0.20Cu0.85-xFex(x=0.10,0.20,0.25,0.40,0.60).粉末X射线衍射(XRD)分析表明,合金含有单一CaCu5型六方结构的LaNi5相,Fe部分替代Cu并没有改变合金的本体相结构,但随着Fe含量的增大,晶格参数a,c和晶胞体积V增大.电化学性能测试表明,随着x增加,合金的放电容量和高倍率放电能力降低,但是循环稳定性得到了显著提高.当x从0.10增加到0.60时,合金的200周循环稳定性(S200)从77.6%提高到89.9%.Fe替代Cu有利于提高合金的循环稳定性,这主要是随着Fe替代量增大,晶胞体积增大,晶格体积膨胀率明显减小,合金的抗粉化能力增强.     

Eu0.5RE0.5Fe0.5Mn0.5O3的57Fe Msosbauer谱研究

利用固相反应合成了Eu0.5RE0.5Fe0.5Mn0.5O3(RE=La,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Y)等化合物。测量了其XRD谱及57FeMssbauer谱。实验发现,随着RE原子序数的增加,样品的晶胞体积减小,Fe在化合物中处于Fe3+的高自旋状态,57Fe的四极裂矩与样品的畸变参数D成线性关系。     

Eu_（0．5）RE_（0．5）Fe_（0．5）Mn_（0．5）O_3的~（57）Fe Msosbauer谱研究

利用固相反应合成了Ｅｕ_（０．５）ＲＥ_（０．５）Ｆｅ_（０．５）Ｍｎ_（０．５）Ｏ_３（ＲＥ＝Ｌａ，Ｐｒ，Ｎｄ，Ｓｍ，Ｅｕ，Ｇｄ，Ｔｂ，Ｄｙ，Ｈｏ，Ｅｒ，Ｔｍ，Ｙｂ，Ｙ）等化合物。测量了其ＸＲＤ谱及~（５７）ＦｅＭｓｓｂａｕｅｒ谱．实验发现，随着ＲＥ原子序数的增加，样品的晶胞体积减小，Ｆｅ在化合物中处于Ｆｅ~（３＋）的高自旋状态，~（５７）Ｆｅ的四极裂矩与样品的畸变参数Ｄ成线性关系。     

Spin-glass behavior in LaFe(x)Co(2-x)P2 solid solutions: interplay between magnetic properties and crystal and electronic structures

To explore the evolution of magnetic properties from ferromagnetic LaCo(2)P(2) to paramagnetic LaFe(2)P(2) (both of ThCr(2)Si(2) structure type) a series of mixed composition LaFe(x)Co(2-x)P(2) (x ≤ 0.5) has been comprehensively investigated by means of single-crystal and powder X-ray and neutron diffraction, magnetization and heat capacity measurements, M?ssbauer spectroscopy, and electronic band structure calculations. The Curie temperature decreases from 132 K in LaCo(2)P(2) to 91 K in LaFe(0.05)Co(1.95)P(2). The ferromagnetic ordering is suppressed at higher Fe content. LaFe(0.1)Co(1.9)P(2) and LaFe(0.2)Co(1.8)P(2) demonstrate spin-glass-like behavior, which was also confirmed by the absence of characteristic features of long-range magnetic ordering, namely, a λ-type anomaly in the heat capacity, a hyperfine splitting in the M?ssbauer spectrum, and magnetic reflections in the neutron diffraction pattern. Finally, both LaFe(0.3)Co(1.7)P(2) and LaFe(0.5)Co(1.5)P(2) exhibit paramagnetic behavior down to 1.8 K. The unit cell parameters of the mixed compounds do not follow the Vegard behavior as the increase in the Fe content results in the decrease of average M-M distances (M = Fe, Co). Quantum-chemical calculations and crystal orbital Hamiltonian population analysis reveal that upon aliovalent (nonisoelectronic) substitution of Fe for Co the antibonding character of M-M interactions is reduced while the Fermi level is shifted below the DOS peak in the 3d metal subband. As the result, at higher Fe content the Stoner criterion is not satisfied and no magnetic ordering is observed.     

LED用Sr(1-1.5x)Mo0.8Si0.2O3.8:Eu3+x红色荧光粉的制备及其荧光性能

通过高温固相法合成了LED用红色荧光粉Sr(1-1.5x)Mo0.8Si0.2O3.8∶Eu3+x（x=0.1,0.2,0.3,0.4,0.5）。 通过XRD、激发光谱和发射光谱测试了材料的物相组成以及发光性能。 x=0.1样品的XRD谱与JCPDS 08-0482(SrMoO4)的标准卡片相同。 Eu3+代替晶格中Sr2+的位置成为发光中心。 随着Eu3+含量x的增加,593 nm处的5D0-7F1跃迁和614 nm处的5D0-7F2跃迁发射强度会相互转换：当x≤0.4时,以磁偶极5D0-7F1跃迁为主,发射橙色光;而当x=0.5时,以电偶极5D0-7F2跃迁发射为主,发射红光。 可能是过量掺杂的Eu3+离子,只能存在于晶格空位形成缺陷,无法占据SrMoO4中Sr2+的格位中,Eu3+在晶格中占据非对称中心的格位,导致电偶极跃迁变成允许跃迁,从而增加了5D0-7F2跃迁,减弱了5D0-7F1跃迁。 因此,可以通过调节激活剂的含量获得不同发光色的荧光粉。 Eu3+掺杂的硅钼酸锶体系,614 nm激发下,在368 nm处出现宽的基质吸收峰和467 nm处7F0-5D2的跃迁峰,且这2处的吸收峰在x=0.5时比x=0.4时强3倍左右。 材料能非常好的吸收368 nm波长的光,产生颜色可调的橙红色。 与近紫外光LED芯片匹配良好。     

Amidinokomplexe von Molybdän(V) und Rhenium(V) Die Kristallstruktur von [Cl4Mo{i-Prop-NC(Cl) N-i-Prop}]

Amidinocomplexes of Molybdenum (V) and Rhenium (V). Crystal Structure of [Cl₄Mo{i-Prop-NC(Cl) N-i-Prop}] Molybdenum pentachloride and rhenium pentachloride, respectively, react with di-isopropylcarbodiimide in CCl₄?suspensions forming the monomeric amidino complexes [Cl₄M{i-prop-NC(Cl)N-i-prop}] (M = Mo, Re). According to the i.r. spectra the C? Cl-amidino ligand is bonded as a chelate. The molybdenum complex is characterized by an X-ray structure determination. It crystallizes in the tetragonalic space group I4₁/a with 8 formula units in the unit cell (1538 independent, observed reflexions, R = 0.051) with the lattice constants a = 1119 and b = 2332 pm.     

High Pressure Synthesis and Characterization of New Members of the RuSr2(RE,Ce)2Cu2O10 Family (RE = Y,Dy)

New members of the RuSr₂(RE_2?x, Ce_x)Cu₂O₁₀ family of magnetically ordered phases have been synthesized under high pressure / high temperature conditions for RE = Y (x = 0.5, 0.7) and Dy (x = 0.5). All compounds show tetragonal symmetry with cell parameters a ≈ 3.82 Å and c ≈ 28.4 Å. Magnetic susceptibility vs temperature measurements show ferromagnetic behaviour of these compounds with T_M = 120–140 K, depending on Ce content. These compounds are semiconducting and tend to transform into insulator, by increasing Ce content, as observed by the temperature dependence of the resistance.     

Structure and physical properties of [micro-tris(1,4-bis(tetrazol-1-yl)butane-N4,N4')iron(II)] bis(hexafluorophosphate), a new Fe(II) spin-crossover compound with a three-dimensional threefold interlocked crystal lattice

[micro-Tris(1,4-bis(tetrazol-1-yl)butane-N4,N4')iron(II)] bis(hexafluorophosphate), [Fe(btzb)(3)](PF(6))(2), crystallizes in a three-dimensional 3-fold interlocked structure featuring a sharp two-step spin-crossover behavior. The spin conversion takes place between 164 and 182 K showing a discontinuity at about T(1/2) = 174 K and a hysteresis of about 4 K between T(1/2) and the low-spin state. The spin transition has been independently followed by magnetic susceptibility measurements, (57)Fe-M?ssbauer spectroscopy, and variable temperature far and midrange FTIR spectroscopy. The title compound crystallizes in the trigonal space group P3 (No. 147) with a unit cell content of one formula unit plus a small amount of disordered solvent. The lattice parameters were determined by X-ray diffraction at several temperatures between 100 and 300 K. Complete crystal structures were resolved for 9 of these temperatures between 100 (only low spin, LS) and 300 K (only high spin, HS), Z = 1 [Fe(btzb)(3)](PF(6))(2): 300 K (HS), a = 11.258(6) A, c = 8.948(6) A, V = 982.2(10) A(3); 100 K (LS), a = 10.989(3) A, c = 8.702(2) A, V = 910.1(4) A(3). The molecular structure consists of octahedral coordinated iron(II) centers bridged by six N4,N4' coordinating bis(tetrazole) ligands to form three 3-dimensional networks. Each of these three networks is symmetry related and interpenetrates each other within a unit cell to form the interlocked structure. The Fe-N bond lengths change between 1.993(1) A at 100 K in the LS state and 2.193(2) A at 300 K in the HS state. The nearest Fe separation is along the c-axis and identical with the lattice parameter c.     

XPS and AES analysis of passive films on Fe-25Cr-X (X = Mo, V, Si and Nb) model alloys

Corrosion resistance of stainless steel is due to the presence of a thin passive film of typically 1–2 nm thickness. The influence of ternary alloying elements on the composition of passive films on Fe-Cr alloys and their pitting corrosion resistance has been investigated. Iron-chromium alloys were analyzed by XPS and AES with model alloys (Fe-25Cr-X with X = at % Mo, Si, V and Nb) formed in sulphate solution in the presence and absence of chloride ions. All ternary alloying elements increase the pitting potential compared to the corresponding binary alloy. Films formed in chloride containing sulphate solution contain both electrolyte anions. Scanning Auger microscopy reveals that for a two phase system such as Fe-25Cr-11Nb, the dendritic phase is enriched with chromium, while essentially all of the niobium is located in the interdendritic eutectic.