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Ismail Ijjaali 《Journal of solid state chemistry》2005,178(5):1503-1507
The quaternary oxychalcogenides Ln4MnOSe6 (Ln=La, Ce, Nd), Ln4FeOSe6 (Ln=La, Ce, Sm), and La4MnOS6 have been synthesized by the reactions of Ln (Ln=La, Ce, Nd, Sm), M (M=Mn, Fe), Se, and SeO2 at 1173 K for the selenides or by the reaction of La2S3 and MnO at 1173 K for the sulfide. Warning: These reactions frequently end in explosions. These isostructural compounds crystallize with two formula units in space group of the hexagonal system. The cell constants (a, c in Å) at 153 K are: La4MnOSe6, 9.7596(3), 7.0722(4); La4FeOSe6, 9.7388(4), 7.0512(5); Ce4MnOSe6, 9.6795(4), 7.0235(5); Ce4FeOSe6, 9.6405(6), 6.9888(4); Nd4MnOSe6, 9.5553(5), 6.9516(5); Sm4FeOSe6, 9.4489(5), 6.8784(5); and La4MnOS6, 9.4766(6), 6.8246(6). The structure of these Ln4MOQ6 compounds comprises a three-dimensional framework of interconnected LnOQ7 bicapped trigonal prisms, MQ6 octahedra, and the unusual LnOQ6 tricapped tetrahedra. 相似文献
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E Gaudin 《Journal of solid state chemistry》2003,175(1):124-131
The compound La2Ca2MnO6(O2) has been synthesized from La2Ca2MnO7 heated at 1123 K under high pressure (4 GPa) with KClO3 as oxygen source. The crystal structure has been refined from X-ray powder data in the space group. The unit-cell parameters are a=5.6335(2) Å and c=17.4879(8) Å. Perpendicular to the c-axis, the structure is built up by the periodic stacking of two close packed [LaO3] layers separated by a layer of composition [Ca2O2] containing (O2)2− peroxide ions. This oxide belongs to the family of compounds formulated as [A′2O2−δ][AnBn−1O3n] for n=2 and δ=0. It is the first member of the series where the thickness of the perovskite slab corresponds to one [BO6] (B=Mn) octahedron. The structural relationships with La2Ca2MnO7 are discussed and the magnetic properties show that in both phases manganese is tetravalent. 相似文献
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Kenzo Kitayama Minehito Kobayashi Hisataka Takano Naomi Nambu Hideyuki Hirasawa 《Journal of solid state chemistry》2003,176(1):151-158
Phase equilibria were established in Ho-Mn-O and Tb-Mn-O systems at 1100°C by varying the oxygen partial pressure from −log(PO2/atm)=0-13.00, and phase diagrams for the corresponding Ln2O3-MnO-MnO2 systems at 1100°C were presented. Stable Ln2O3, MnO, Mn3O4, LnMnO3, and LnMn2O5 phases were found at 1100°C, whereas Ln2Mn2O7, Ln2MnO4, Mn2O3, and MnO2 were not found to be stable. Small nonstoichiometric ranges were found in the LnMnO3 phase, with the composition of LnMnO3 represented as functions of log(PO2/atm), and . Activities of the components in the solid solution were calculated from these equations. The composition of LnMnO3 may range from Ln2O3 rich to Ln2O3 poor, while MnO is slightly nonstoichiometric, being oxygen rich and LnMn2O5 seems to be nonstoichiometric. Lattice constants of LnMnO3 quenched at different oxygen partial pressures and of LnMn2O5 quenched in air were determined. The standard Gibbs energy changes of the reactions appearing in the phase diagrams were also calculated. The relationship between the tolerance factor of LnMnO3 and ΔG0of reaction, (1/2)Ln2O3+MnO+(1/4)O2=LnMnO3, is shown graphically. 相似文献
5.
Five members of Ln5/8M3/8MnO3 series with A-cation size variance (σ2) ranging between 3×10−4 and 71×10−4 Å2, and the same A-cation size , have been synthesized by the ceramic method. The five manganites are single phase and they crystallize in the Pnma perovskite superstructure. The five compositions display ferromagnetic-paramagnetic transitions at temperatures ranging between 130 and 270 K, for the highest and lowest variance sample, respectively. The samples with smaller variances show sharp magnetization transitions and the samples with the larger variances display broad transitions. These transitions have also been studied by differential scanning calorimetry, DSC, and some enthalpy changes are reported. The resistivity study indicates that all samples display the expected metal-to-insulator transitions at temperatures ranging between 140 and 270 K. The samples have been analysed at room temperature by ultra-high-resolution synchrotron powder diffraction and the structural and microstructural features are reported. Furthermore, Nd5/8Sr0.255Ca0.12MnO3 () and Sm0.225Nd0.4Sr0.308Ca0.067MnO3 () samples have also been studied by synchrotron powder diffraction at 140 K, below the transition temperatures. Both samples are found to be single phase above and below the transition by ultra-high-resolution synchrotron powder diffraction. The microstructure of the samples has been investigated through Williamson-Hall plots. Sample broadenings are markedly anisotropic and strongly dominated by microstrains with average values of the Δd/d term close to 14×10−4. A direct correlation is found between the microstrain values and the widths of the magnetization transitions. 相似文献
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Evan Lyle Thomas Andrew N. Bankston Peter Klavins David P. Young Julia Y. Chan 《Journal of solid state chemistry》2006,179(6):1642-1649
Ln3Co4Sn13 (Ln=La, Ce) have been synthesized by flux growth and characterized by single crystal X-ray diffraction. These compounds adopt the Yb3Rh4Sn13-type structure and crystallize in the cubic space group (No. 223) with Z=2. Lattice parameters at 298 K are , , and , for the La and Ce analogues, respectively. The crystal structure consists of an Sn-centered icosahedron at the origin of the unit cell, which shares faces with eight Co trigonal prisms and 12 Ln-centered cuboctahedra. Magnetization data at 0.1 T show paramagnetic behavior down to 1.8 K for Ce3Co4Sn13, with per Ce3+, while conventional type II superconductivity appears below 2.85 K in the La compound. Electrical resistivity and specific heat data for the La compound show a corresponding sharp superconducting transition at Tc∼2.85 K. The entropy and resistivity data for Ce3Co4Sn13 show the existence of the Kondo effect with a complicated semiconducting-like behavior in the resistivity data. In addition, a large enhanced specific heat coefficient at low T with a low magnetic transition temperature suggests a heavy-fermionic character for the Ce compound. Herein, the structure and physical properties of Ln3Co4Sn13 (Ln=La, Ce) are discussed. 相似文献
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Yuki Shimoda 《Journal of solid state chemistry》2009,182(10):2873-2879
New quadruple perovskite oxides Ba4LnIr3O12 (Ln=lanthanides) were prepared and their magnetic properties were investigated. They crystallize in the monoclinic 12L-perovskite-type structure with space group C2/m. The Ir3O12 trimers and LnO6 octahedra are alternately linked by corner-sharing and form the perovskite-type structure with 12 layers. The Ln and Ir ions are both in the tetravalent state for Ln=Ce, Pr, and Tb compounds , and for other compounds (Ln=La, Nd, Sm-Gd, Dy-Lu), Ln ions are in the trivalent state and the mean oxidation state of Ir ions is . An antiferromagnetic transition has been observed for Ln=Ce, Pr, and Tb compounds at 10.5, 35, and 16 K, respectively, while the other compounds are paramagnetic down to 1.8 K. 相似文献
9.
The novel compound Ca2Co1.6Ga0.4O5 with brownmillerite (BM) structure has been prepared from citrates at 950 °C. The crystal structure of Ca2Co1.6Ga0.4O5 was refined, from neutron powder diffraction (NPD) data, in space group Pnma, , , , χ2=1.798, , Rwp=0.0378 and Rp=0.0292. On the basis of the NPD refinement the compound was found to be a G-type antiferromagnet (space group Pn′m′a) at room temperature, with the magnetic moments of cobalt atoms directed along chains of tetrahedra in the BM structure. Electron diffraction and electron microscopy studies revealed disorder in the crystallites, which can be interpreted as the presence of slabs with BM-type structure of Pnma and I2mb symmetry. 相似文献
10.
The rare-earth dicyanamides Ln[N(CN)2]3 (Ln=La, Ce, Pr, Nd, Sm, Eu) were obtained via ion exchange in aqueous medium and subsequent drying: The crystal structures were solved and refined based on X-ray powder diffraction data and they were found to be isotypic: Ln[N(CN)2]3; Cmcm (no. 63), Z=4, Ln=La: , , ; Ce: , , ; Pr: , , ; Nd: , , ; Sm: , , ; Eu: , , ). The compounds represent the first dicyanamides with trivalent cations. The Ln3+ ions are coordinated by three bridging N atoms and six terminal N atoms of the dicyanamide ions forming a three capped trigonal prism. The structure type is related to that of PuBr3. The novel compounds Ln[N(CN)2]3 have been characterized by IR and Raman spectroscopy (Ln=La) and the thermal behavior has been monitored by differential scanning calorimetry (Ln=Ce, Nd, Eu). 相似文献
11.
Artem M. Abakumov Marta D. Rossell Sergey Yu. Vassiliev Gustaaf Van Tendeloo 《Journal of solid state chemistry》2006,179(2):421-428
Phase transitions in the elpasolite-type K3AlF6 complex fluoride were investigated using differential scanning calorimetry, electron diffraction and X-ray powder diffraction. Three phase transitions were identified with critical temperatures , and . The α-K3AlF6 phase is stable below T1 and crystallizes in a monoclinic unit cell with a=18.8588(2)Å, b=34.0278(2)Å, c=18.9231(1)Å, β=90.453(1)° (a=2ac−cc, b=4bc, c=ac+2cc; ac, bc, cc—the basic lattice vectors of the face-centered cubic elpasolite structure) and space group I2/a or Ia. The intermediate β phase exists only in very narrow temperature interval between T1 and T2. The γ polymorph is stable in the T2<T<T3 temperature range and has an orthorhombic unit cell with a=36.1229(6)Å, b=17.1114(3)Å, c=12.0502(3)Å (a=3ac−3cc, b=2bc, c=ac+cc) at 250 °C and space group Fddd. Above T3 the cubic δ polymorph forms with ac=8.5786(4)Å at 400 °C and space group . The similarity between the K3AlF6 and K3MoO3F3 compounds is discussed. 相似文献
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Ingo Hartenbach Sabine Strobel Peter K. Dorhout 《Journal of solid state chemistry》2008,181(10):2828-2836
The fluoride-derivatized lanthanoid(III) ortho-oxomolybdates(VI) LnF[MoO4] (Ln=Sm-Tm) crystallize in the monoclinic space group P21/c with four formula units per unit cell (a=516-528 pm, b=1220-1248 pm, c=659-678 pm, β=112.5-113.1°). The structure contains one crystallographically unique Ln3+ cation surrounded by two fluoride and six oxide anions in a square antiprism (CN=8). The square antiprisms [LnF2O6] are interconnected via three edges to form layers parallel (010), which are cross-linked along [010] by Mo6+ in tetrahedral oxygen coordination to form the three-dimensional crystal structure. The fluoride anions within this arrangement exhibit a twofold coordination of Ln3+ cations in the shape of a boomerang, which is connected to another F− anion to form planar [F2Ln2]4+ rhombuses. Magnetic measurements for GdF[MoO4], TbF[MoO4], and DyF[MoO4] show Curie-Weiss behavior, despite the peculiar arrangement of the lanthanoid(III) cations in layers comparable with those of gray arsenic. Furthermore, Raman, infrared, and diffuse reflectance spectroscopy data for these compounds were recorded and interpreted. 相似文献
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Kenny Ståhl Tonci Balic-Zunic K. Michael Eriksen Rasmus Fehrmann 《Journal of solid state chemistry》2005,178(5):1697-1704
The crystal structures of K2S2O7, KNaS2O7 and Na2S2O7 have been solved and/or refined from X-ray synchrotron powder diffraction data and conventional single-crystal data. K2S2O7: From powder diffraction data, monoclinic C2/c, Z=4, a=12.3653(2), b=7.3122(1), , β=93.0792(7)°, RBragg=0.096. KNaS2O7: From powder diffraction data; triclinic , Z=2, a=5.90476(9), b=7.2008(1), , α=101.7074(9), β=90.6960(7), γ=94.2403(9)°, RBragg=0.075. Na2S2O7: From single-crystal data; triclinic , Z=2, a=6.7702(9), b=6.7975(10), , α=116.779(2), β=96.089(3), γ=84.000(3)°, RF=0.033. The disulphate anions are essentially eclipsed. All three structures can be described as dichromate-like, where the alkali cations coordinate oxygens of the isolated disulphate groups in three-dimensional networks. The K-O and Na-O coordinations were determined from electron density topology and coordination geometry. The three structures have a cation-disulphate chain in common. In K2S2O7 and Na2S2O7 the neighbouring chains are antiparallel, while in KNaS2O7 the chains are parallel. The differences between the K2S2O7 and Na2S2O7 structures, with double-, respectively single-sided chain connections and straight, respectively, corrugated structural layers can be understood in terms of the differences in size and coordinating ability of the cations. 相似文献
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Mohammad El-khateeb Khaled Shawakfeh Heinrich Lang 《Journal of organometallic chemistry》2006,691(18):3743-3748
The hydrosulfido complexes CpRu(L)(L′)SH react with one equivalent of O-alkyl oxalyl chlorides (ROCOCOCl) to form the corresponding O-alkylthiooxalate complexes CpRu(L)(L′)SCOCO2R (L = L′ = PPh3 (1), (2); L = PPh3, L′ = CO (3); R = Me (a), Et (b)). The reactions of the hydrosulfido complexes with half equivalent of oxalyl chloride produce the bimetallic complexes [CpRu(L)(L′)SCO]2 (L = L′ = PPh3 (4), (5); L = PPh3, L′ = CO (6)). The crystal structures of CpRu(PPh3)2SCOCO2Me (1a) and CpRu(dppe)SCOCO2Et (2b) are reported. 相似文献
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A new Os-containing, pillared perovskite, La5Os3MnO16, has been synthesized by solid state reaction in sealed quartz tubes. This extends the crystal chemistry of these materials which had been known only for Mo and Re, previously. The crystal structure has been characterized by X-ray and neutron powder diffraction and is described in space group C-1 with parameters a=7.9648(9) Å; b=8.062(1) Å; c=10.156(2) Å, α=90.25(1)°, β=95.5(1)°; γ=89.95(2)°, for La5Os3MnO16. The compound is isostructural with the corresponding La5Re3MnO16 phase. A very short Os-Os distance of 2.50(1) Å was found in the dimeric pillaring unit, Os2O10, suggestive of a triple bond as demanded by electron counting. Nearly spin only values for the effective moment for Os5+ () and Mn2+ () were derived from magnetic susceptibility data. Evidence for magnetic transitions was seen near ∼180 and 80 K. Neutron diffraction data indicate that Tc is 170(5) K. The magnetic structure of La5Os3MnO16 at 7 K was solved revealing that Os5+ and Mn2+ form ferrimagnetically coupled layers with antiferromagnetic interlayer ordering. The ordered moments are for Mn2+ and for Os5+, which are reduced from the respective spin only values of 5.0 and . The observation of net ferrimagnetic (antiparallel) intraplanar coupling between Os5+(t2g3) and Mn2+(t2g3eg2) is interesting as it appears to contradict the Goodenough-Kanamori rules for 180° superexchange. 相似文献
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The organic-inorganic hybrid materials vanadium oxide [VIVO2(phen)2]·6H2O (1) and [(2,2′-bipy)2VVO2](H2BO3)·3H2O (2) have been conventional and hydrothermal synthesized and characterized by single crystal X-ray diffraction, elemental analyses, respectively. Although the method and the ligand had been used in the syntheses of the compounds (1) and (2) are different, they almost possess similar structure. They all exhibit the distorted octahedral [VO2N4] unit with organonitrogen donors of the phen and 2,2′-bipy ligands, respectively, which coordinated directly to the vanadium oxide framework. And they are both non-mixed-valence complexes. But the compound (1) is isolated, and the compound (2) consists of a cation of [(2,2′-bipy)2VVO2]+ and an anion of (H2BO3)−. So the valence of vanadium of (1) and (2) are tetravalence and pentavalence, respectively. Meanwhile it is noteworthy that π-π stacking interaction between adjacent phen and 2,2′-bipy groups in compounds 1 and 2 also play a significant role in stabilization of the structure. Thus, the structure of [VIVO2(phen)2]·6H2O and [(2,2′-bipy)2VVO2](H2BO3)·3H2O are both further extended into interesting three-dimensional supramolecular. Crystal data: (1) Triclinic, a=8.481(4), b=12.097(5), and α=66.32(2), β=82.97(3), and γ=82.59(4)°, Z=2, R1=0.0685, wR2=0.1522. (2) Triclinic, a=6.643(13), b=11.794(2), and α=101.39(3), β=101.59(3), and γ=97.15(3)°, Z=2, R1=0.0736, wR2=0.1998. 相似文献
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The first member of the Ruddlesden-Popper family, Ca2MnO4, has been revisited. Coexistence of two structures has been shown from electron microscopy at room temperature and neutron diffraction data have evidenced two antiferromagnetic structures at low temperature. Two forms, with an orthorhombic Aba2 ( and c≈12 Å) and a tetragonal I41/cad ( and c≈24 Å) symmetries, were found to coexist coherently within the same matrix. 相似文献
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B. Chapelet-Arab G. Nowogrocki S. Grandjean 《Journal of solid state chemistry》2004,177(11):4269-4281
Three new alkaline earth-zirconium oxalates M2Zr(C2O4)4·nH2O have been synthesized by precipitation methods for M=Ba, Sr, Ca. For each compound the crystal structure was determined from single crystals obtained by controlled diffusion of M2+ and Zr4+ ions through silica gel containing oxalic acid. Ba2Zr(C2O4)4·7H2O, monoclinic, space group C2/c, a=9.830(2), b=29.019(6), , , , Z=4, R=0.0427; Sr2Zr(C2O4)4·11H2O, tetragonal, space group I41/acd, a=16.139(4), , ,Z=8, R=0.0403; Ca2Zr(C2O4)4·5H2O, orthorhombic, space group Pna21, a=8.4181(5), b=15.8885(8), , , Z=4, R=0.0622. The structures of the three compounds consist of chains of edge-shared MO6(H2O)x (x=2 or 3) polyhedra connected to ZrO8 polyhedra through oxalate groups. Depending on the arrangement of chains, the ZrO8 polyhedron geometry (dodecahedron or square antiprism) and the connectivity, two types of three-dimensional frameworks are obtained. For the smallest M2+ cations (Sr2+, Ca2+), large tunnels are obtained, running down the c direction of the unit cell, which can accommodate zeolitic water molecules. For the largest Ba2+ cation, the second framework is formed and is closely related to that of Pb2Zr(C2O4)4·nH2O. The decomposition at 800°C into strontium carbonate, barium carbonate or calcium oxide and MZrO3 (M=Sr, Ba, Ca) perovskite is reported from thermal analyses studies and high temperature X-ray powder diffraction. 相似文献
20.
Paul H. Tobash 《Journal of solid state chemistry》2007,180(5):1575-1581
Reported are the flux synthesis, the crystal structure determination, the properties and the band structure calculations of a new polymorph of CaGe2, which crystallizes with the hexagonal space group P63mc (no. 186) with cell parameters of a=3.9966(9) and c=10.211(4) Å (Z=2; Pearson's code hP6). The structure can be viewed as puckered layers of three-bonded germanium atoms, , which are stacked along the direction of the c-axis in an ABAB-fashion. The germanium polyanionic layers are separated by the Ca cations. As such, this structure is closely related to the structure of the other CaGe2 polymorph, which crystallizes with the rhombohedral CaSi2 type in the R3¯m space group (No. 166), where the layers are arranged in an AA′BB′CC′-fashion, and are also interspaced by Ca2+ cations. LMTO calculations suggest that in spite of the formal closed-shell configuration for all atoms and the apparent adherence to the Zintl rules for electron counting, i.e., Ca2+[3b-Ge1−]2), the phase will be a poor metal due to a small Ca-3d-Ge-4p band overlap. Magnetic susceptibility measurements as a function of the temperature indicate that the new CaGe2 polymorph exhibits weak, temperature independent, Pauli-paramagnetism. 相似文献