Ternary arsenides A2Zn2As3 (A = Sr, Eu) and their stuffed derivatives A2Ag2ZnAs3

The ternary arsenides A(2)Zn(2)As(3) and the quaternary derivatives A(2)Ag(2)ZnAs(3) (A = Sr, Eu) have been prepared by stoichiometric reaction of the elements at 800 °C. Compounds A(2)Zn(2)As(3) crystallize with the monoclinic Ba(2)Cd(2)Sb(3)-type structure (Pearson symbol mC28, space group C2/m, Z = 4; a = 16.212(5) ?, b = 4.275(1) ?, c = 11.955(3) ?, β = 126.271(3)° for Sr(2)Zn(2)As(3); a = 16.032(4) ?, b = 4.255(1) ?, c = 11.871(3) ?, β = 126.525(3)° for Eu(2)Zn(2)As(3)) in which CaAl(2)Si(2)-type fragments, built up of edge-sharing Zn-centered tetrahedra, are interconnected by homoatomic As-As bonds to form anionic slabs [Zn(2)As(3)](4-) separated by A(2+) cations. Compounds A(2)Ag(2)ZnAs(3) crystallize with the monoclinic Yb(2)Zn(3)Ge(3)-type structure (Pearson symbol mC32, space group C2/m; a = 16.759(2) ?, b = 4.4689(5) ?, c = 12.202(1) ?, β = 127.058(1)° for Sr(2)Ag(2)ZnAs(3); a = 16.427(1) ?, b = 4.4721(3) ?, c = 11.9613(7) ?, β = 126.205(1)° for Eu(2)Ag(2)ZnAs(3)), which can be regarded as a stuffed derivative of the Ba(2)Cd(2)Sb(3)-type structure with additional transition-metal atoms in tetrahedral coordination inserted to link the anionic slabs together. The Ag and Zn atoms undergo disorder but with preferential occupancy over four sites centered in either tetrahedral or trigonal planar geometry. The site distribution of these metal atoms depends on a complex interplay of size and electronic factors. All compounds are Zintl phases. Band structure calculations predict that Sr(2)Zn(2)As(3) is a narrow band gap semiconductor and Sr(2)Ag(2)ZnAs(3) is a semimetal. Electrical resistivity measurements revealed band gaps of 0.04 eV for Sr(2)Zn(2)As(3) and 0.02 eV for Eu(2)Zn(2)As(3), the latter undergoing an apparent metal-to-semiconductor transition at 25 K.     

Ternary rare-earth manganese bismuthides: structures and physical properties of RE(3)MnBi(5) (RE = La-Nd) and Sm(2)Mn(3)Bi(6)

Investigations in the ternary RE-Mn-Bi systems where RE is an early rare earth element have revealed the existence of the polybismuthides RE3MnBi5 (RE = La-Nd), previously known only for the Ce member, and the new compound Sm2Mn3Bi6. Their structures were determined from single-crystal X-ray diffraction data. The RE3MnBi5 compounds adopt the hexagonal inverse Hf5Cu3Sn-type structure (Pearson symbol hP18, space group P63/mcm, a = 9.7139(11)-9.5438(16) A, c = 6.4883(7)-6.4089(11) A for RE = La-Nd), containing chains of face-sharing Mn-centered octahedra. Sm2Mn3Bi6 adopts a new monoclinic structure type (Pearson symbol mP22, space group P21/m, a = 10.3917(8) A, b = 4.4557(3) A, c = 13.2793(10) A, beta = 108.0100(10) degrees ) in which the Mn centers are coordinated by Bi atoms in diverse geometries (distorted octahedral, trigonal bipyramidal, and distorted tetrahedral (seesaw)) and participate in extensive metal-metal bonding in the form of chains of Mn3 clusters. Homoatomic bonding interactions involving nominally anionic Bi atoms are manifested as one-dimensional Bi chains in RE3MnBi5 and as four-atom-wide Bi ribbons in Sm2Mn3Bi6. Electrical resistivity measurements on single crystals revealed metallic behavior with prominent transitions near 40 K for RE3MnBi5 and 50 K for Sm2Mn3Bi6. Magnetic susceptibility measurements showed that Pr3MnBi5 undergoes magnetic ordering near 25 K.     

Layered rare-earth gallium antimonides REGaSb(2) (RE = La--Nd, Sm).

The ternary rare-earth gallium antimonides, REGaSb(2) (RE = La--Nd, Sm), have been synthesized through reaction of the elements. The structures of SmGaSb(2) (orthorhombic, space group D(5)(2)-C222(1), Z = 4, a = 4.3087(5) A, b = 22.093(4) A, c = 4.3319(4) A) and NdGaSb(2) (tetragonal, space group D(19)(4h)-I4(1)/amd, Z = 8, a = 4.3486(3) A, c = 44.579(8) A) have been determined by single-crystal X-ray diffraction. The SmGaSb(2)-type structure is adopted for RE = La and Sm, whereas the NdGaSb(2)-type structure is adopted for RE = Ce--Nd. The layered SmGaSb(2) and NdGaSb(2) structures are stacking variants of each other. In both structures, two-dimensional layers of composition (2)(infinity)[GaSb] are separated from square nets of Sb atoms [Sb] by RE atoms. Alternatively, the structures may be considered as resulting from the insertion of zigzag Ga chains between (2)(infinity)[RE Sb(2)] slabs. In SmGaSb(2), all of the Ga chains are parallel and the (2)(infinity)[SmSb(2)] layers are stacked in a ZrSi(2)-type arrangement. In NdGaSb(2), the Ga chains alternate in direction, resulting in a doubling of the long axis relative to SmGaSb(2), and the (2)(infinity)[NdSb(2)] layers are stacked in a Zr(3)Al(4)Si(5)-type arrangement. Extended Hückel band structure calculations are used to explain the bonding in the [GaSb(2)](3-) substructure.     

A Comparative Study of Two New Structure Types. Synthesis and Structural and Electronic Characterization of K(RE)P(2)Se(6) (RE = Y, La, Ce, Pr, Gd)

Two polytypes of potassium rare-earth-metal hexaselenodiphosphates(IV), K(RE)P(2)Se(6) (RE = Y, La, Ce, Pr, Gd), have been synthesized from the stoichiometric reaction of RE, P, Se, and K(2)Se(4) at 750 degrees C. Both single-crystal and powder X-ray diffraction analyses showed that the structures of these polytypes vary with the size of the rare earth metals. For the smaller rare-earth metals, Y and Gd, K(RE)P(2)Se(6) crystallized in the orthorhombic space group P2(1)2(1)2(1). The yttrium compound was studied by single-crystal X-ray diffraction with the cell parameters a = 6.7366(5) ?, b = 7.4286(6) ?, c = 21.603(2) ?, and Z = 4. This structure type comprises a layered, square network of yttrium atoms that are bound to four distinct [P(2)Se(6)](4)(-) units through selenium bonding. Each [P(2)Se(6)](4)(-) unit possesses a Se atom that is not bound to any Y atom but is pointing out into the interlayer spacing, into an environment of potassium cations. For larger rare-earth metals, La, Ce, and Pr, K(RE)P(2)Se(6) crystallized in a second, monoclinic polytype, the structure of which has been published. Both of these two different polytypes can be related to each other and several other isoelectronic chalcophosphate structures based on a Parthé valence electron concentration analysis. These structures include Ag(4)P(2)S(6), K(2)FeP(2)S(6), and the hexagonal M(II)PS(3) structure types. The magnetic susceptibilities of the title compounds have been studied, and the behavior can been explained based on a simple set of unpaired f-electrons. The diffuse reflectance spectroscopy also showed that these yellow plates are moderately wide band gap ( approximately 2.75 eV) semiconductors.     

Ternary rare-earth titanium antimonides RE2Ti(11-x)Sb(14+x) (RE = Sm, Gd, Tb, Yb)

The isostructural rare-earth titanium antimonides RE 2Ti 11 - x Sb 14 + x ( RE = Sm, Gd, Tb, Yb) have been synthesized by arc-melting reactions of the elements. Single-crystal X-ray diffraction revealed that they adopt a new structure type (Pearson symbol oP54, space group Pnma, Z = 2; a = 15.8865(6)-15.9529(9) A, b = 5.7164(2)-5.7135(3) A, c = 12.9244(5)-12.9442(7) A for RE = Sm-Yb). The structure consists of titanium-centered octahedra (CN6) and pentagonal bipyramids (CN7) connected to form a 3D framework whose cavities are filled with RE atoms. 1D linear skewers of titanium atoms, within face-sharing octahedral chains, and similar skewers of antimony atoms, associated with the titanium-centered pentagonal bipyramids, extend along the b direction. On proceeding from Sm 2Ti 11Sb 14 to Tb 2Ti 10.41(1)Sb 14.59(1) and Yb 2Ti 10.58(1)Sb 14.42(1), antimony atoms are disordered within some of the titanium sites. Resistivity measurements on the samarium and ytterbium members indicated metallic behavior.     

A New Family of Nonstoichiometric Layered Rare-Earth Tin Antimonides, RESn(x)()Sb(2) (RE = La, Ce, Pr, Nd, Sm): Crystal Structure of LaSn(0.75)Sb(2)

A new class of nonstoichiometric layered ternary rare-earth tin antimonides, RESn(x)()Sb(2) (RE = La, Ce, Pr, Nd, Sm), has been synthesized through reaction of the elements at 950 degrees C. In the lanthanum series LaSn(x)()Sb(2), tin can be incorporated from a maximum content of x approximately 0.7 or 0.8 to as low as x approximately 0.10. The structure of lanthanum tin diantimonide with the maximum tin content, LaSn(0.75)Sb(2), has been determined by single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group -Cmcm with a = 4.2425(5) ?, b = 23.121(2) ?, c = 4.5053(6) ?, and Z = 4. The isostructural rare-earth analogues were characterized by powder X-ray diffraction. The structure of LaSn(0.75)Sb(2) comprises layers of composition "LaSb(2)" in which La atoms are coordinated by Sb atoms in a square-antiprismatic geometry. Between these layers reside chains of Sn atoms distributed over three crystallographically independent sites, each partially occupied at about 20%. The structure of LaSn(0.75)Sb(2) can be regarded as resulting from the excision of RE-Sb and Sb-Sb bonds in the related structures of binary rare-earth diantimonides, RESb(2), and then intercalation of Sn atoms between layers.     

Structure and physical properties of ternary rare-earth cobalt bismuth intermetallics (RE)12Co5Bi (RE = Y, Gd, Tb, Dy, Ho, Er, Tm)

The rare-earth intermetallic compounds (RE)12Co5Bi (RE = Y, Gd, Tb, Dy, Ho, Er, Tm) were prepared by arc-melting and annealing at 600 degrees C. These compounds extend the previously known (RE)6M2+xX1-x (M = Co, Ni; X = Ga, In, Sn, Pb) series with the Ho6Co2Ga-type structure to X = Bi. The crystal structure of Ho12Co5Bi was refined by the Rietveld method from powder X-ray diffraction data obtained using synchrotron radiation (Pearson symbol oI36, orthorhombic, space group Immm, Z = 2, a = 9.37598(14) A, b = 9.37871(14) A, c = 9.85465(13) A). Unlike other Ho6Co2Ga-type compounds, the 2a site in Ho12Co5Bi is exclusively occupied by Co atoms. Four-probe electrical resistivity measurements on sintered polycrystalline samples of (RE)12Co5Bi indicated metallic behavior. Magnetic measurements revealed behavior ranging from frequency-dependent maxima in the ac susceptibility for Y12Co5Bi to possible ferrimagnetic ordering for Gd12Co5Bi to antiferromagnetic ordering with metamagnetic transitions for the remaining compounds. As confirmed by band structure calculations using Y12Co5Bi as a model compound, Y-Y and Y-Co interactions are the most important bonding components, but matrix effects are likely responsible for anomalously short Co-Co contacts in the structure.     

Closely related rare-earth metal germanides RE2Li2Ge3 and RE3Li4Ge4 (RE = La-Nd, Sm): synthesis, crystal chemistry, and magnetic properties

Reported are the syntheses, crystal structures, and magnetic susceptibilities of two series of closely related rare-earth metal-lithium germanides RE(2)Li(2)Ge(3) and RE(3)Li(4)Ge(4) (RE = La-Nd, Sm). All title compounds have been synthesized by reactions of the corresponding elements at high temperatures, and their structures have been established by single-crystal X-ray diffraction. RE(2)Li(2)Ge(3) phases crystallize in the orthorhombic space group Cmcm (No. 63) with the Ce(2)Li(2)Ge(3) structure type, while the RE(3)Li(4)Ge(4) phases crystallize in the orthorhombic space group Immm (No. 71) with the Zr(3)Cu(4)Si(4) structure type, respectively. Both of their structures can be recognized as the intergrowths of MgAl(2)Cu- and AlB(2)-like slabs, and these traits of the crystal chemistry are discussed. Temperature-dependent direct-current magnetization measurements indicate Curie-Weiss paramagnetism in the high-temperature regime for RE(2)Li(2)Ge(3) and RE(3)Li(4)Ge(4) (RE = Ce, Pr, Nd), while Sm(2)Li(2)Ge(3) and Sm(3)Li(4)Ge(4) exhibit Van Vleck-type paramagnetism. The data are consistent with the local-moment magnetism expected for RE(3+) ground states. At temperatures below ca. 20 K, magnetic ordering transitions have been observed. The experimental results have been complemented by tight-binding linear muffin-tin orbital electronic-band-structure calculations.     

Synthesis, structure, chemical bonding, and magnetism of the series RELiGe2 (RE = La-Nd, Sm, Eu)

This article focuses on the synthesis and the crystal chemistry of six members of a series of rare-earth metal based germanides with general formula RELiGe(2) (RE = La-Nd, Sm, and Eu). The structures of these compounds have been established by single-crystal X-ray diffraction (CaLiSi(2) structure type, space group Pnma, Z = 4, Pearson symbol oP16). The chemical bonding within this atomic arrangement can be rationalized in terms of anionic germanium zigzag chains, conjoined via chains of edge-shared LiGe(4) tetrahedra and separated by rare-earth metal cations. The structure can also be viewed as an intergrowth of AlB(2)-like and TiNiSi-like fragments, or as the result of the replacement of 50% of the rare-earth metal atoms by lithium in the parent structure of the REGe monogermanides. Except for LaLiGe(2) and SmLiGe(2), the remaining four RELiGe(2) phases exhibit Curie-Weiss paramagnetism above about 50 K. In the low temperature regime, the localized 4f electrons in CeLiGe(2), PrLiGe(2), and SmLiGe(2) order ferromagnetically, while antiferromagnetic ordering is observed for NdLiGe(2) and EuLiGe(2). The calculated effective magnetic moments confirm RE(3+) ground states in all cases excluding EuLiGe(2), in which the magnetic response is consistent with Eu(2+) configuration (J = S = 7/2). The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB-LMTO) band structure calculations.     

Structures and physical properties of rare-earth zinc antimonides Pr6Zn(1+x)Sb(14+y) and RE6Zn(1+x)Sb14 (RE = Sm, Gd-Ho)

A new series of isostructural ternary rare-earth zinc antimonides RE(6)Zn(1+x)Sb(14+y) (RE = Pr, Sm, Gd-Ho) has been obtained by direct reaction of the elements at 1050-1100 degrees C. Single-crystal X-ray diffraction studies revealed that these compounds adopt an orthorhombic structure type (space group Immm (no. 71), Z = 2, a = 4.28-4.11 A, b = 15.15-14.73 A, c = 19.13-18.56 A in the progression from RE = Pr to Ho) that may be regarded as stuffed variants of a (U(0.5)Ho(0.5))(3)Sb(7)-type host structure. Columns of face-sharing RE(6) trigonal prisms, centered by Sb atoms, occupy channels defined by an extensive polyanionic Sb network. This network is constructed from three-atom-wide and four-atom-wide Sb strips, the latter being linked together by single Sb atoms in RE(6)Zn(1+x)Sb(14) (RE = Sm, Gd-Ho; y = 0), but also by additional Sb-Sb pairs in a disordered fashion in Pr(6)Zn(1+x)Sb(14+y) (y = approximately 0.6). Interstitial Zn atoms then partially fill tetrahedral sites (occupancy of 0.5-0.7) and, to a lesser extent, square pyramidal sites (occupancy of 0.04-0.12), accounting for the observed nonstoichiometry with variable x. Except for the Gd member, these compounds undergo antiferromagnetic ordering below T(N) < 9 K, with the magnetic susceptibilities of the Tb, Dy, and Ho members following the Curie-Weiss law above T(N). For the Ho member, the thermal conductivities are low and the Seebeck coefficients are small and positive, implying p-type character consistent with the occurrence of partial Zn occupancies. At low temperatures (down to 5 K), electrical resistivity measurements for the Tb, Dy, and Ho members indicated metallic behavior, which persists at high temperatures (up to 560 K) for the Ho member. Band structure calculations on an idealized "Gd(6)Zn(2)Sb(14)" model revealed the existence of a pseudogap near the Fermi level.     

REMGa3Ge and RE3Ni3Ga8Ge3 (M = Ni, Co; RE = rare-earth element): new intermetallics synthesized in liquid gallium. X-ray, electron, and neutron structure determination and magnetism

New quaternary intermetallic phases REMGa(3)Ge (1) (RE = Y, Sm, Tb, Gd, Er, Tm; M = Ni, Co) and RE(3)Ni(3)Ga(8)Ge(3) (2) (RE = Sm, Gd) were obtained from exploratory reactions involving rare-earth elements (RE), transition metal (M), Ge, and excess liquid Ga the reactive solvent. The crystal structures were solved with single-crystal X-ray and electron diffraction. The crystals of 1 and 2 are tetragonal. Single-crystal X-ray data: YNiGa(3)Ge, a = 4.1748(10) A, c = 23.710(8) A, V = 413.24(2) A(3), I4/mmm, Z = 4; Gd(3)Ni(3)Ga(8)Ge(3), a = 4.1809(18) A, c = 17.035(11) A, V = 297.8(3) A(3), P4/mmm, Z = 1. Both compounds feature square nets of Ga atoms. The distribution of Ga and Ge atoms in the REMGa(3)Ge was determined with neutron diffraction. The neutron experiments revealed that in 1 the Ge atoms are specifically located at the 4e crystallographic site, while Ga atoms are at 4d and 8g. The crystal structures of these compounds are related and could be derived from the consecutive stacking of disordered [MGa](2) puckered layers, monatomic RE-Ge planes and [MGa(4)Ge(2)] slabs. Complex superstructures with modulations occurring in the ab-plane and believed to be associated with the square nets of Ga atoms were found by electron diffraction. The magnetic measurements show antiferromagnetic ordering of the moments located on the RE atoms at low temperature, and Curie-Weiss behavior at higher temperatures with the values of mu(eff) close to those expected for RE(3+) free ions.     

稀土－铌(钽)复合溴氧化物的结构与光谱特性

用高温固相法合成了系列化合物RE_0.06La_0.94M₂O₆Br(M=Nb,Ta;RE=Eu,Tb,Pr,Sm),并测定了其激发和发射光谱,室温下Eu³⁺、Tb³⁺、Pr³⁺、Sm³⁺在稀土-铌(钽)复合溴氧化物中呈现特征激发谱线,但Nb和Ta的光谱特性稍有不同。     

Zr(7)Sb(4): a new binary zirconium-rich antimonide

Zr(7)Sb(4) has been prepared by arc-melting of the elemental components and annealing at 1000-1150 degrees C. Its crystal structure was determined by X-ray diffraction (Pearson symbol mP44, monoclinic, space group P2(1)/c, Z = 4, a = 8.4905(6) A, b = 11.1557(8) A, c = 11.1217(8) A, beta = 111.443(2) degrees at 295 K). Zr(7)Sb(4) is isotypic to Hf(6)TiSb(4), a compound stabilized by differential fractional site occupancy. It is the first binary group-4 antimonide with this metal-to-antimony ratio, but it differs from the corresponding phosphides and arsenides M(7)Pn(4) (M = Ti, Zr, Hf; Pn = P, As), which adopt the Nb(7)P(4)-type structure. Zr(7)Sb(4) is built up from layers excised from the tetragonal W(5)Si(3)-type structure; these layers are displaced relative to each other to maximize interlayer Zr-Zr and Zr-Sb bonding, as confirmed by band structure calculations.     

Ternary arsenides a(2)zn(5)as(4) (a = k, rb): zintl phases built from stellae quadrangulae

Stoichiometric reaction of the elements at high temperature yields the ternary arsenides K(2)Zn(5)As(4) (650 °C) and Rb(2)Zn(5)As(4) (600 °C). They adopt a new structure type (Pearson symbol oC44, space group Cmcm, Z = 4; a = 11.5758(5) ?, b = 7.0476(3) ?, c = 11.6352(5) ? for K(2)Zn(5)As(4); a = 11.6649(5) ?, b = 7.0953(3) ?, c = 11.7585(5) ? for Rb(2)Zn(5)As(4)) with a complex three-dimensional framework of linked ZnAs(4) tetrahedra generating large channels that are occupied by the alkali-metal cations. An alternative and useful way of describing the structure is through the use of stellae quadrangulae each consisting of four ZnAs(4) tetrahedra capping an empty central tetrahedron. These compounds are Zintl phases; band structure calculations on K(2)Zn(5)As(4) and Rb(2)Zn(5)As(4) indicate semiconducting behavior with a direct band gap of 0.4 eV.     

Diverse closed cavities in condensed rare earth metal-chalcogenide matrixes: Cs[Lu7Q11] and (ClCs6)[RE21Q34] (RE = Dy, Ho; Q = S, Se, Te)

Two types of novel ordered chalcogenids Cs[Lu(7)Q(11)] (Q = S, Se) and (ClCs(6))[RE(21)Q(34)] (RE = Dy, Ho; Q = S, Se, Te) were discovered by high-temperature solid state reactions. The structures were characterized by single-crystal X-ray diffraction data. Cs[Lu(7)Q(11)] crystallize in the orthorhombic Cmca (no. 64) with a = 15.228(4)-15.849(7) ?, b = 13.357(3)-13.858(6) ?, c = 18.777(5)-19.509(8) ?, and Z = 8. (ClCs(6))[RE(21)Q(34)] crystallize in the monoclinic C2/m (no. 12) with a = 17.127(2)-18.868(2) ?, b = 19.489(2)-21.578(9) ?, c = 12.988(9)-14.356(2) ?, β = 128.604(2)-128.738(4)°, and Z = 2. Both types of compounds feature 3D RE-Q network structures that embed with dual tricapped cubes Cs(2)@Se(18) in the former or unprecedented matryoshka nesting doll structure cavities of (ClCs(6))@Se(32) in the latter. The band gap, band structure, as well as a structure change trend of the majority of A/RE/Q compounds are presented.     

La0.5>RE0.3Sr0.2FeO3－δ (RE = Nd、Ce、Sm)体系双稀土阴极材料的制备与电性能

采用甘氨酸-硝酸盐法(GNP)合成了La0.5RE0.3Sr0.2FeO3－δ(RE=Nd、Ce、Sm)系列复合氧化物粉体. 用X射线衍射(XRD)和TG-DSC分析了样品钙钛矿物相的形成过程, 用Archimedes排水法测量体积密度并计算烧结样品的相对密度, 用四端子技术测量电导率. 结果显示, 掺Nd的样品1200 ℃烧结2 h成为单一立方钙钛矿结构, 掺Ce样品有明显的CeO2立方相析出, 掺Sm样品主相为钙钛矿结构伴有微弱的杂峰. 1250 ℃烧结2 h的La0.5Nd0.3Sr0.2FeO3－δ在600 ℃时电导率高达100 S•cm-1以上, 明显高于La0.5Ce0.3Sr0.2FeO3－δ及La0.5Sm0.3Sr0.2FeO3－δ样品的电导率, 预示着La0.5Nd0.3Sr0.2FeO3－δ可能是一种良好的中温固体氧化物燃料电池(SOFC)阴极材料.     

REAu2In4 (RE = La, Ce, Pr, Nd): polyindides from liquid indium

The series of compounds REAu2In4 (RE = La, Ce, Pr, Nd) crystallize from excess In as rod-shaped single crystals. All members adopt the orthorhombic space group Pnma with a = 18.506(2) A, b = 4.6865(6) A, and c = 7.3414(9) A for LaAu2In4, a = 18.514(3) A, b = 4.6624(8) A, and c = 7.389(1) A for CeAu2In4, a = 18.420(4) A, b = 4.6202(9) A, and c = 7.376(2) A for the Pr analogue, and a = 18.406(2) A, b = 4.6114(5) A, and c = 7.4073(7) A for NdAu2In4. The REAu2In4 series can be regarded as polar intermetallic phases composed of a complex [Au2In4]3- polyanion network in which the rare-earth ions are embedded. The [Au2In4]3- network features In tetramer units, which defines the compounds as polyindides. Magnetic measurements found no magnetic ordering down to 2 K for any of the compounds. In addition, LaAu2In4 was found to be Pauli paramagnetic with a small susceptibility. Ab initio density functional methods were used to carry out electronic structure calculations to explore the bonding, the role of gold, and the contributions of different atoms to the density of states near the Fermi energy. We find that the density of states decreases slowly near Ef and reaches a minimum at about 0.5 eV above Ef.     

Large-scale synthesis of single-crystalline RE2O3 (RE=Y, Dy, Ho, Er) nanobelts by a solid-liquid-phase chemical route

Yttrium-group heavy rare-earth sesquioxide (RE(2)O(3), RE=Y, Dy, Ho, Er) nanobelts were successfully fabricated by thermolysis of solid RE(NO(3))(3)x H(2)O in a dodecylamine/1-octadecene mixed solvent system. The synthetic principle is based on separating the nucleation and growth processes by utilizing the poor solubility of RE(NO(3))(3)chi H(2)O in the solvent mixture and the heat-transportation difference between the liquid and solid. By using dodecylamine, RE(2)O(3) nanobelts can be readily obtained. X-ray diffraction (XRD) analysis shows that the synthesized RE(2)O(3) nanobelts are body-centered cubic and crystalline. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selective-area electron diffraction (SAED), and high-resolution transmission electron microscopy (HR-TEM) demonstrate that the synthesized RE(2)O(3) compounds possess regular geometric structure (beltlike) with perfect crystallinity. Preliminary experimental results prove that the dodecylamine plays a key role in the formation of RE(2)O(3) nanobelts and cannot be replaced by other surfactants. Furthermore, this method can be extended to the synthesis of RE(2)O(3) nanobelt/metal nanocrystal nanocomposites and ABO(3) (A=Y, Dy, Ho, Er; B=Al) and A(3)B(5)O(12) (A=Y, Dy, Ho, Er; B=Al)-type ternary oxide nanobelts, using mixed-metal nitrate salts in the correct stoichiometry instead of single rare-earth nitrates.     

Synthesis, crystal chemistry, and magnetic properties of RE7Li8Ge10 and RE11Li12Ge16 (RE = La-Nd, Sm): new members of the [REGe2](n)[RELi2Ge](m) homologous series

Eight new rare-earth metal-lithium-germanides belonging to the [REGe(2)](n)[RELi(2)Ge](m) homologous series have been synthesized and structurally characterized by single-crystal X-ray diffraction. The structures of the title compounds can be rationalized as linear intergrowths of imaginary RELi(2)Ge (MgAl(2)Cu structure type) and REGe(2) (AlB(2) structure type) slabs. The compounds with general formula RE(7)Li(8)Ge(10) (RE = La-Nd, Sm), i.e., [REGe(2)](3)[RELi(2)Ge](4), crystallize in the orthorhombic space group Cmmm (No. 65) with a new structure type. Similarly, the compounds with general formula RE(11)Li(12)Ge(16) (RE = Ce-Nd), i.e., [REGe(2)](5)[RELi(2)Ge](6), crystallize in the orthorhombic space group Immm (No. 71) also with its own structure type. Temperature-dependent DC magnetization measurements indicate Curie-Weiss paramagnetism in the high-temperature regime and hint at complex magnetic ordering at low temperatures. The measured effective moments are consistent with RE(3+) ground states in all cases. The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB-LMTO) electronic structure calculations.     

Gd5-xYxTt4 (Tt = Si or Ge): effect of metal substitution on structure, bonding, and magnetism

A crystallographic study and theoretical assessment of the Gd/Y site preferences in the Gd 5- x Y x Tt 4 ( Tt = Si, Ge) series prepared by high-temperature methods is presented. All structures for the Gd 5- x Y x Si 4 system belong to the orthorhombic, Gd 5Si 4-type (space group Pnma). For the Gd 5- x Y x Ge 4 system, phases with x < 3.6 and x >or= 4.4 adopt the orthorhombic, Sm 5Ge 4-type structure. For the composition range of 3.6 相似文献