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1.
Single crystals of the title compounds were prepared by solid state reactions from barium carbonate and ruthenium metal using a BaBr2 flux and investigated by X-ray diffraction method using Mo(Kα) radiation and a Charge Coupled Device (CCD) detector. A structural model for the term n=2, Ba5Ru2Br2O9 (1) was established in the hexagonal symmetry, space group P63/mmc, a=5.8344(2) Å, c=25.637(2) Å, Z=2. Combined refinement and maximum-entropy method (MEM) unambiguously show the presence of CO32− ions in the three other compounds (2, 3, 4). Their crystal structures were solved and refined in the trigonal symmetry, space group , a=5.8381(1) Å, c=15.3083(6) Å for the term n=3, Ba6Ru3Br1.54(CO3)0.23O12 (2), and space group , a=5.7992(1) Å, c=52.866(2) Å and a=5.7900(1) Å, c=59.819(2) Å for the terms n=4, Ba7Ru4Br1.46(CO3)0.27O15 (3), and n=5, Ba8Ru5Br1.64(CO3)0.18O18 (4), respectively. The structures are formed by the periodic stacking along [0 0 1] of (n+1) hexagonal close-packed [BaO3] layers separated by a double layer of composition [Ba2Br2−2x(CO3)x]. The ruthenium atoms occupy the n octahedral interstices created in the hexagonal perovskite slabs and constitute isolated dimers Ru2O9 of face-shared octahedra (FSO) in 1 and isolated trimers Ru3O12 of FSO in 2. In 3 and 4, the Ru2O9 units are connected by corners either directly (3) or through a slab of isolated RuO6 octahedra (4) to form a bidimensional arrangement of RuO6 octahedra. These four oxybromocarbonates belong to the family of compounds formulated [Ba2Br2−2x(CO3)x][Ban+1RunO3n+3] where n represents the thickness of the octahedral string in hexagonal perovskite slabs. These compounds are compared to the oxychloride series. 相似文献
2.
Meghan C. Knapp 《Journal of solid state chemistry》2006,179(4):1076-1085
Unlike ordering of the octahedral B-site cations, ordering of the larger A-site cations in stoichiometric perovskites is rare. Herein the A- and B-site ordering characteristics of several double perovskites with AA′BB′O6 stoichiometry have been investigated. The compounds investigated include NaLaMgWO6, NaLaMgTeO6, NaLaScNbO6, NaLaScSbO6, NaLaTi2O6, and NaLaZr2O6. Group theoretical methods are used to enumerate the possible structures of AA′BB′X6 double perovskites that result from the combination of rock salt ordering of the B-site cations, layered ordering of the A-site cations, and octahedral tilting distortions. This combination results in 12 possible structures in addition to the aristotype. Among the compounds investigated only NaLaMgWO6 and NaLaScNbO6 show significant long-range ordering of the A-site cations, Na+ and La3+. A complete structural characterization is presented for NaLaMgWO6. This compound possesses monoclinic C2/m (#12) space group symmetry, with unit cell dimensions of , , , β=90.136(1)° at room temperature. The results presented here show that in AA′BB′O6 perovskites layered ordering of A-site cations creates a bonding instability that is compensated for by a second-order Jahn-Teller distortion of the B′ cation. These two distortions are synergistic and the removal of one leads to the disappearance of the other. 相似文献
3.
A new oxide, Bi14Sr21Fe12O61, with a layered structure derived from the 2212 modulated type structure Bi2Sr3Fe2O9, was isolated. It crystallizes in the I2 space group, with the following parameters: a=16.58(3) Å, b=5.496(1) Å, c=35.27(2) Å and β=90.62°. The single crystal X-ray structure determination, coupled with electron microscopy, shows that this ferrite is the m=5 member of the [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] collapsed family. This new collapsed structure can be described as slices of 2212 structure of five bismuth polyhedra thick along , shifted with respect to each other and interconnected by means of [Bi4Sr6Fe2O16] slices. The latter are the place of numerous defects like iron or strontium for bismuth substitution; they can be correlated to intergrowth defects with other members of the family. 相似文献
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6.
N. Tancret 《Journal of solid state chemistry》2004,177(3):806-816
Single crystals of the title compounds were prepared using a BaCl2 flux and investigated by X-ray diffraction methods using MoKα radiation and a charge coupled device (CCD) detector. The crystal structures of these two new compounds were solved and refined in the hexagonal symmetry with space group P63/mmc, a=5.851(1) Å, c=25.009(5) Å, ρcal=4.94 g cm−3, Z=2 to a final R1=0.069 for 20 parameters with 312 reflections for Ba5Ru2Cl2O9 and space group , a=5.815(1) Å, c=14.915(3) Å, ρcal=5.28 g cm−3, Z=1 to a final R1=0.039 for 24 parameters with 300 reflections for Ba6Ru3Cl2O12. The structure of Ba5Ru2Cl2O9 is formed by the periodic stacking along [001] of three hexagonal close-packed BaO3 layers separated by a double layer of composition Ba2Cl2. The BaO3 stacking creates binuclear face-sharing octahedra units Ru2O9 containing Ru(V). The structure of Ba6Ru3Cl2O12 is built up by the periodic stacking along [001] of four hexagonal close-packed BaO3 layers separated by a double layer of composition Ba2Cl2. The ruthenium ions with a mean oxidation degree +4.67 occupy the octahedral interstices formed by the four layers hexagonal perovskite slab and then constitute isolated trinuclear Ru3O12 units. These two new oxychlorides belong to the family of compounds formulated as [Ba2Cl2][Ban+1RunO3n+3], where n represents the thickness of the octahedral string in hexagonal perovskite slabs. 相似文献
7.
Synthesis and single crystal structures of ternary phosphides Li4SrP2 and AAeP (A=Li, Na; Ae=Sr, Ba)
Yongkwan Dong 《Journal of solid state chemistry》2007,180(2):432-439
Two new (NaSrP, Li4SrP2) and two known (LiSrP, LiBaP) ternary phosphides have been synthesized and characterized using single crystal X-ray diffraction studies. NaSrP crystallizes in the non-centrosymmetric hexagonal space group (#189, a=7.6357(3) Å, c=4.4698(3) Å, V=225.69(2) Å3, Z=3, and R/wR=0.0173/0.0268). NaSrP adopts an ordered Fe2P structure type. PSr6 trigonal prisms share trigonal (pinacoid) faces to form 1D chains. Those chains define large channels along the [001] direction through edge-sharing. The channels are filled by chains of PNa6 face-sharing trigonal prisms. Li4SrP2 crystallizes in the rhombohedral space group (#166, a=4.2813(2) Å, c=23.437(2) Å, V=372.04(4) Å3, Z=3, and R/wR=0.0142/0.0222). In contrast to previous reports, LiSrP and LiBaP crystallize in the centrosymmetric hexagonal space group P63/mmc (#194, a=4.3674(3) Å, c=7.9802(11) Å, V=131.82(2) Å3, Z=2, and R/wR=0.0099/0.0217 for LiSrP; a=4.5003(2) Å, c=8.6049(7) Å, V=150.92(2) Å3, Z=2, and R/wR=0.0098/0.0210 for LiBaP). Li4SrP2, LiSrP, and LiBaP can be described as Li3P derivatives. Li atoms and P atoms make a graphite-like hexagonal layer, . In LiSrP and LiBaP, Sr or Ba atoms reside between layers to substitute for two Li atoms of Li3P, while in Li4SrP2, Sr substitutes only between every other layer. 相似文献
8.
Hui Zhang Liang Fang R. Dronskowski R.Z. Yuan 《Journal of solid state chemistry》2004,177(11):4007-4012
Some dielectric oxides have been synthesized and characterized in the BaO-La2O3-TiO2-Nb2O5 system. Through Rietveld refinement of X-ray powder diffraction data, Ba5LaTi2Nb3O18 and Ba4La2Ti3Nb2O18 are identified as the AnBn−1O3n (n=6) type cation-deficient perovskites with space group and lattice constants , and for Ba5LaTi2Nb3O18; , and for Ba4La2Ti3Nb2O18, respectively. Their ceramics exhibit high dielectric constant up to 57 and high quality factors (Qf) up to 21,273 GHz. The temperature coefficient of resonant frequency (τf) of these ceramics is decreased with the increase of B-site bond valence. 相似文献
9.
The new compound Sr5(As2O7)2(AsO3OH) was synthesized under hydrothermal conditions. It represents a previously unknown structure type and belongs to a group of a few compounds in the system SrO-As2O5-H2O; (As2O7)4− besides (AsO3OH)2− groups have not been described yet. The crystal structure of Sr5(As2O7)2(AsO3OH) was determined by single-crystal X-ray diffraction (space group P21/n, a=7.146(1), b=7.142(1), , β=93.67(3)°, , Z=4). One of the five symmetrically unique Sr atoms is in a trigonal antiprismatic (Inorg. Chem. 35 (1996) 4708)—coordination, whereas the other Sr atoms adopt the commonly observed (“Collect” data collection software, Delft, The Netherlands, 1999; Methods Enzymol. 276 (1997) 307)—coordination. The position of the hydrogen atom was located in a difference Fourier map and subsequently refined with an isotropic displacement parameter. Worth mentioning is the very short hydrogen bond length Oh-H?O(1) of 2.494(4) Å; it belongs to the shortest known examples where the donor and acceptor atoms are crystallographically different. This hydrogen bond was confirmed by IR spectroscopy. In addition, Raman spectra were collected in order to study the arsenate groups. 相似文献
10.
We describe the preparation and structural characterization of four In-containing perovskites from neutron powder diffraction (NPD) and X-ray powder diffraction (XRPD) data. Sr3In2B″O9 and Ba(In2/3B″1/3)O3 (B″=W, U) were synthesized by standard ceramic procedures. The crystal structure of the W-containing perovskites and Ba(In2/3U1/3)O3 have been revisited based on our high-resolution NPD and XRPD data, while for the new U-containing perovskite Sr3In2UO9 the structural refinement was carried out from high-resolution XRPD data. At room temperature, the crystal structure for the two Sr phases is monoclinic, space group P21/n, where the In atoms occupy two different sites Sr2[In]2d[In1/3B″2/3]2cO6, with a=5.7548(2) Å, b=5.7706(2) Å, c=8.1432(3) Å, β=90.01(1)° for B″=W and a=5.861(1) Å, b=5.908(1) Å, c=8.315(2) Å, β=89.98(1)° for B″=U. The two phases with A=Ba should be described in a simple cubic perovskite unit cell (S.G. Pm3¯m) with In and B″ distributed at random at the octahedral sites, with a=4.16111(1) Å and 4.24941(1) Å for W and U compounds, respectively. 相似文献
11.
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
12.
Composition- and temperature-dependent phase transitions in 1:3 ordered perovskites Ba4−xSrxNaSb3O12
A series of 25 members of the 1:3 ordered perovskite family of the type Ba4−xSrxNaSb3O12 has been synthesized and their structures determined using synchrotron X-ray and neutron powder diffraction techniques. At room temperature the sample Ba4NaSb3O12 has a cubic structure in space group with a=8.2821(1) Å, where the Na and Sb cations are ordered in the octahedral sites but there is no tilting of the (Na/Sb)O6 octahedra. As the average size of the A-site cation decreases, through the progressive replacement of Ba by Sr, tilting of the octahedra is introduced firstly lowering the symmetry to tetragonal in P4/mnc then to orthorhombic in Cmca and ultimately a monoclinic structure in P21/n as seen for Sr4NaSb3O12 with a=8.0960(2) Å, b=8.0926(2) Å, c=8.1003(1) Å and β=90.016(2)°. The powder neutron diffraction studies show that the orthorhombic and tetragonal phases in Cmca and P4/mnc co-exist at room temperature for samples with x between 1.5 and 2. 相似文献
13.
Martin Pley 《Journal of solid state chemistry》2005,178(10):3206-3209
RuO4 was prepared by oxidation of elemental ruthenium. Two different modifications were obtained and investigated by X-ray single crystal diffraction. RuO4-I has cubic symmetry , and two independent tetrahedral molecules are present in the unit cell. Within the standard uncertainties in both molecules the distances Ru-O are 1.695 Å. The second modification, RuO4-II, is monoclinic and isotypic with OsO4. There is one independent molecule in the unit cell, which shows distances Ru-O of 1.697 and 1.701 Å, respectively. 相似文献
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Hui Wu 《Journal of solid state chemistry》2004,177(11):4305-4315
Single-phase 1:2 B-site ordered perovskites are formed in the (1−x)A2+(Li1/4Nb3/4)O3-(x)A2+(Li2/5W3/5)O3 systems, A2+=Sr and Ca, within the range 0.238?x?0.333. The X-ray and electron diffraction patterns are consistent with a P21/c monoclinic supercell, , , , β≈125°, where the 1:2 order is combined with b−b−c+ octahedral tilting. Rietveld refinements of the ordered A(BI1/3BII2/3)O3 structures give a good fit to a model with BI occupied by Li and Nb, BII by W and Nb, and a general stoichiometry (Sr,Ca)(Li3/4+y/2Nb1/4−y/2)1/3(Nb1−yWy)2/3O3, y=0.9x=0.21-0.30. The Sr system also includes regions of stability of a 1:3 ordered phase for 0.0?x?0.111, and a 1:1 ordered double perovskite for 0.833?x?1.0. The formation of the non-stoichiometric 1:2 ordered phases is associated with the large site charge/size differences that can be accessed in these systems, and restricted by local charge imbalances at the A-sites for W-rich compositions. These concepts are used to generate stability maps to rationalize the formation of the known 1:2 ordered oxide perovskites. 相似文献
16.
The structures of NaRu2O4 and Na2.7Ru4O9 are refined using neutron diffraction. NaRu2O4 is a stoichiometric compound consisting of double chains of edge sharing RuO6 octahedra. Na2.7Ru4O9 is a non-stoichiometric compound with partial occupancy of the Na sublattice. The structure is a mixture of single, double and triple chains of edge-shared RuO6 octahedra. NaRu2O4 displays temperature independent paramagnetism with . Na2.7Ru4O9 is paramagnetic, χ0= with and a Curie constant of 0.0119 emu/mol Oe K. Specific heat measurements reveal a small upturn at low temperatures, similar to the upturn observed in La4Ru6O19. The electronic contribution to the specific heat (γ) for Na2.7Ru4O9 was determined to be15 mJ/moleRu K2. 相似文献
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18.
《Journal of solid state chemistry》2003,173(1):203-208
Single crystals of a new complex oxide, Sr18Ru1.9Bi4.1O33, were precipitated from a mixture of molten alkali and alkaline earth metal hydroxides at 750°C. The structure was determined from a ruby-red crystal using single-crystal X-ray diffraction. Sr18Ru1.88Bi4.12O33 crystallizes in the space group C2/c (monoclinic) and has unit-cell dimensions: a=10.2102(11) Å, b=17.882(2) Å, c=19.579(2) Å, and β=102.043(2)°. The structure (refined to R1=4.5%, wR2=9.2%) is an unusual ABO3 defect perovskite, with th of the oxygen positions vacant. All the A sites and half of the B sites are occupied by Sr2+, while the remaining B sites are occupied by Bi5+ or Ru5+. The oxygen atom vacancies are located within the Bi coordination sphere exclusively. The bonding in the BO3 sublattice is less covalent than that in the perovskite archetype from which it is derived due to the presence of 50% Sr2+ on the B sites. Thus, the structure of Sr18Ru1.9Bi4.1O33 can also be viewed as being made up of isolated bismuthate anions (BiO55−, BiO5.56− and BiO67−) and ruthenate anions (RuO67−) separated by strontium cations. 相似文献
19.
The structures of the Ba2InNbO6, Sr2InNbO6 and Ca2InNbO6 “1:1” complex perovskites have been refined from neutron powder diffraction data. Both the A=Ca and Sr compounds occur at room temperature in P121/n1 (a=ap+bp, b=-ap+bp, c=2cp) perovskite-related superstructures while the A=Ba compound occurs in the , a=2ap, elpasolite structure type. In the case of the A=Ca compound, an extensive Ca2[(Ca2x/3In1−xNbx/3)Nb]O6 ‘solid solution’ field spanning compositions between Ca4Nb2O9 and Ca2InNbO6 in the CaO-InO3/2-NbO5/2 ternary phase diagram is shown to exist. Under the conditions of synthesis used, the ‘solid solution’ field stops just short of the ideal 1:1 Ca2InNbO6 composition. 相似文献
20.
The solid-state synthesis of the oxyfluoride Nb3O5F5, its crystal structure determined from X-ray powder diffraction data as well as some physical characterizations, are reported. Nb3O5F5 constitutes the term n=3 of the NbnO2n−1Fn+2 series related to the Dion-Jacobson phases. It crystallizes, at room temperature, in the tetragonal system (space group I4/mmm (no. 139); Z=4; a=3.9135(1) Å, c=24.2111(2) Å, and V=370.80(3) Å3). The crystal structure appears to be an in-between of the three-dimensional network of NbO2F and the two-dimensional packing of NbOF3 (term n=1 of the NbnO2n−1Fn+2 series). This layered structure consists of slabs made of three Nb(O,F)6 corner-linked octahedra in thickness (n=3) shifted one from another by a ()/translation. Oxygen and fluorine atoms are randomly distributed over all the ligand sites. 相似文献