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1.
Peter Ziegler Katharina Gibson Aivaras Kareiva 《Journal of solid state chemistry》2004,177(10):3610-3615
The compounds BiMO2NO3, with M=Pb, Ca, Sr, and Ba, were obtained as single-phase products from solid-state reactions in an atmosphere of nitrous gases. The oxide nitrates with Pb and Ca crystallize in the tetragonal space group I4/mmm with two formula units per unit cell; the oxide nitrates with Sr and Ba crystallize in the orthorhombic space group Cmmm with four formula units per unit cell. Lattice parameters at room temperature are a=397.199(4), c=1482.57(2) pm for M=Pb; a=396.337(5), c=1412.83(3) pm for M=Ca; a=1448.76(3), b=567.62(1), c=582.40(1) pm for M=Sr and a=1536.50(8), b=571.67(3), c=597.55(3) pm for M=Ba. The structures, which were refined by powder X-ray diffraction, consist of alternating [BiMO2]+ and [NO3]− layers stacked along the direction of the long axis. IR and thermogravimetric data are also given. The various M2+ cations in BiMO2NO3 are compatible with each other; therefore and because of their layer-type structure, these compounds are interesting precursors for oxide materials, e.g., the HTSC compounds (Bi,Pb)2Sr2Can−1CunOx. 相似文献
2.
《Solid State Sciences》2007,9(7):564-573
High pressure and temperature are used to synthesise perovskite related phases in the Sr–Cr(IV)–O system. The n = 1, 2 and ∞ members of the Srn+1CrnO3n+1 family have been obtained. Another new member, n = 3 as well as an hexagonal layered perovskite have also been observed by transmission electron microscopy and electron diffraction. The average structure of Sr3Cr2O7 as determined by XRD has space group I4/mmm, whereas its microstructure includes a large amount of defects both in the layer stacking and within the layers. 2D magnetism and a large electrical resistance in Sr3Cr2O7 are observed as opposed to the nonlocalized electronic behaviour of SrCrO3. 相似文献
3.
The room temperature structures of the five layer Aurivillius phases A2Bi4Ti5O18 (A=Ca, Sr, Ba and Pb) have been refined from powder neutron diffraction data using the Rietveld method. The structures consist of [Bi2O2]2+ layers interleaved with perovskite-like [A2Bi2Ti5O16]2− blocks. The structures were refined in the orthorhombic space group B2eb (SG. No. 41), Z=4, and the unit cell parameters of the oxides are a=5.4251(2), b=5.4034(1), c=48.486(1); a=5.4650(2), b=5.4625(3), c=48.852(1); a=5.4988(3), b=5.4980(4), c=50.352(1); a=5.4701(2), b=5.4577(2), c=49.643(1) for A=Ca, Sr, Ba and Pb, respectively. The structural features of the compounds were found similar to n=2-4 layers bismuth oxides. The strain caused by mismatch of cell parameter requirements for the [Bi2O2]2+ layers and perovskite-like [A2Bi2Ti5O16]2− blocks were relieved by tilting of the TiO6 octahedra. Variable temperature synchrotron X-ray studies for Ca and Pb compounds showed that the orthorhombic structure persisted up to 675 and 475 K, respectively. Raman spectra of the compounds are also presented. 相似文献
4.
The phases LaxSr2−xFeyRu1−yO4±δ (x=0.2-0.8; y=0.6-0.9) have been synthesized by solid-state techniques and yield tetragonal structures with I4/mmm symmetry. The oxygen stoichiometry and high-temperature structures have been examined using diffraction techniques and in situ Mössbauer spectroscopy at temperatures up to ∼600°C. Furthermore, new reduced phases that adopt structures with Immm symmetry have been discovered. Unusual coordination numbers have been determined for the most highly reduced samples with square planar coordination evident for the B site cations. The reduced orthorhombic Immm phases were found to readily reoxidize in air to the tetragonal I4/mmm structure at relatively low temperatures of only ∼500°C. 相似文献
5.
Azadeh Askarinejad 《Journal of organometallic chemistry》2006,691(17):3563-3566
A two-dimensional polymer, [Tl3(μ-BPC)2(μ-NO3)]n [BPC = biphenyl-2-carboxylate], has been synthesized and characterized. Its single-crystal X-ray structure shows three types of TlI-ions with coordination numbers of 5 (Tl1 and Tl2), and 4 (Tl3). Two of the thallium atoms, Tl1 and Tl3, contain close TlI?π (aromatic) contacts, thus attaining a total hapticity of 11 and 10 with environments Tl1O5C6 and Tl3O4C6, respectively. 相似文献
6.
L. Ya. Gavrilova T. V. Aksenova V. A. Cherepanov 《Russian Journal of Inorganic Chemistry》2008,53(6):953-958
Phase equilibria in systems La-M-Fe-O (M = Ca or Sr) at 1100° in air were studied. The homogeneity ranges and structures of solid solutions La1 ? x M x FeO3 ? δ (0 ≤ x ≤ 0.3 for M = Ca and 0 ≤ x ≤ 0.8 for M = Sr), Sr2 ? y La y FeO4 ? δ (0.8 ≤ y ≤ 1.0), and Sr3 ? z La z Fe2O7 ? δ (0 ≤ z ≤ 0.2) were determined using X-ray powder diffraction. The structural parameters of complex oxides were refined using the full-profile Rietveld technique. Correlations between the unit cell parameters and the compositions of solid solutions were derived. Isobaric/isothermal phase diagrams were constructed for systems La-M-Fe-O (M = Ca or Sr) at 1100°C in air. 相似文献
7.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1983,39(2):167-172
The non-ionized forms of tetradentate Schiff bases NN′-ethylenebis(salicylideneimine), H2L and NN′-propane-1,3-diylbis(salicylideneimine), H2L′ react with hydrated alkaline earth halide and nitrate to give complexes of the type: M(H2L)Cl2·nH2O [M = Mg(II), Ca(II), Sr(II); n = 0–4], M(H2L)2Cl2 [M = Ca(II), Sr(II), M(H2L)nBr2 [M = Ca(II), Sr(II); n = 2, 3 and Mg2(H2L)3Br4], M(H2L)nI2 [M = Mg(II), Ca(II), Sr(II), Ba(II); n = 2, 3)], M(H2L)n(NO3)2 and M(H2L′)n(NO1)2[M = Mg(II), Ca(II);n = 1, 2)]. Because of distinct spectral similarities with structurally known Ca(H2L′)(NO3)2 compound, the Schiff bases are coordinated through the negatively charged phenolic oxygen atoms and not the nitrogen atoms of the azomethine groups, which carry the protons transferred from phenolic groups on complexation. Halide and nitrate are coordinated to the central metal ion except in 2:1 nitrato complexes where the presence of both ionic and coordinated nitrate groups are evident and also in 3:1 halide complexes where the presence of non-coordinated halide cannot be excluded. X-Ray powder photographs showed no marked similarities between Ca(H2L′)(NO3)2 and Mg(H2L′)(NO3)2 while there are some isomorphic features between the same types of halide complexes. Infrared spectra and other structural information revealed the polymeric nature of the complexes. Therefore the coordination numbers exhibited by the alkaline earth metal cations would be 4, 6 or 8 in these series of Schiff base complexes. 相似文献
8.
Investigations are reported on polymerizations of 2- and 4- vinylpyridine, styrene and butadiene by a series of related alkaline earth metal initiators, Ph3CMX(THF)n (M = Ca, Ba, X = Cl, n = 2; M = Ca, X = Br, n = 4; M = Sr, X = Cl, n = 4; M = Sr, X = Br, n = 5) in tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME) at various temperatures and in the absence of solvent. The polymers have been examined by GPC and aspects of their microstructures determined by 13C and/or 1H NMR spectroscopy and, for polybutadiene, i.r. spectroscopy. Poly-2-vinylpyridine produced by Ph3CMX(THF)n is rich in isotactic content; the isotacticity is higher for polymer formed in THF than DME solution, falls with change of initiator in the order M = Ca > Sr > Ba and, in DME, is greater when X = Br. The tacticities of poly-4-vinylpyridine and polystyrene are similar to those obtained from related organometallic initiators. The 1,4-content of polybutadiene decreases with initiator Ph3CMX(THF)n in the order M = Ba > Sr > Ca; the trans-1,4 structure generally predominates except when M = Ba from which cis-1,4 links are formed in comparable amounts. 相似文献
9.
《Solid State Sciences》2000,2(5):587-594
Tl4Cu4(P2O7)3 has the following crystallographic features: orthorhombic space group Pcca with a=20.171(2), b=10.558(1), c=9.676(1) Å and Z=4. A total of 1303 reflections with I>2(I) were used for structure solution and refinements. The agreement factors R1 and WR2 converged to 0.040 and 0.093, respectively. GOF=1.103. Tl4Cu4(P2O7)3 presents a three-dimensional structure, its anionic framework consists of corner sharing CuO5 polyhedra and P2O7 groups delimiting several types of interconnected tunnels wherein the thallium cations reside. 相似文献
10.
Tomohiro Mitsuyama 《Journal of solid state chemistry》2008,181(6):1419-1424
Partial replacement of alkaline metals in anhydrous KCa2Ta3O10 and LiCa2Ta3O10 was studied to control interlayer hydration and photocatalytic activity for water splitting under UV irradiation. A′1−xNaxCa2Ta3O10·nH2O (A′=K and Li) samples were synthesized by ion exchange of CsCa2Ta3O10 in mixed molten nitrates at 400 °C. In K1−xNaxCa2Ta3O10·nH2O, two phases with the orthorhombic (C222) and tetragonal (I4/mmm) structures were formed at x?0.7 and x?0.5, respectively. Upon replacement by Na+ having a larger enthalpy of hydration (ΔHh0), the interlayer hydration occurred at x?0.3 and the hydration number (n) was increased monotonically with an increase of x. Li1−xNaxCa2Ta3O10·nH2O showed a similar hydration behavior, but the phase was changed from I4/mmm (x<0.5, n∼0) via P4/mmm (x∼0.5, n∼1) to I4/mmm (x∼1.0, n∼2). The photocatalytic activities of these systems after loading 0.5 wt% Ni were quite different each other. K1−xNaxCa2Ta3O10·nH2O exhibited the activity increasing in consistent with n, whereas Li1−xNaxCa2Ta3O10·nH2O exhibited the activity maximum at x=0.77, where the rates of H2/O2 evolution were nearly doubled compared with those for end-member compositions (x=0 and 1). 相似文献
11.
In order to clarify the effect of PbO addition on the formation steps of the superconducting phases in the system Bi2O3?SrO?CaO?CuO, a study of solid-state reactions under non-isothermal conditions, in the PbO?MO (M=Ca, Sr, Ca+Sr) system has been carried out. Results suggest that the reactivity of the components in the system containing PbO and CaO is much higher than in the system containing SrO. The Ca2PbO4 compound is formed first even in the system whereM=Ca+Sr. It is confirmed that Ca2PbO4 systems containing PbO. 相似文献
12.
Shalabh Gupta 《Journal of solid state chemistry》2006,179(6):1924-1930
Two new antimony based intermetallic phases, Ca8.63(5)Sr2.37Sb10(1) and Ca3.66(7)Sr7.34Sb10(2), crystallizing in Ho11Ge10 structure type (tetragonal, I4/mmm) have been synthesized and characterized. Although both Ca11Sb10 and Sr11Sb10 are known to be isostructural (Ho11Ge10 structure type) and hence all Ca sites should be accessible to Sr as well, it appears that certain sites are preferentially ordered by Ca in the mixed (Ca/Sr)11Sb10 compounds reported here. The crystal structure of Ca8.63(5)Sr2.37Sb10 and Ca3.66(7)Sr7.34Sb10 has been solved from single crystal X-ray data using direct methods and refined using full-matrix least-squares method. The structure can be described as bonded network of A-Sb (A=Ca, Sr) with Sb existing as isolated Sb3−, diantimony and square units. Simple valence electron count reveals these compounds to be Zintl phases. It is found that the larger Sr or Sr/Ca ions preferentially occupy sites that are closer to the diantimony anions as compared to the smaller Ca ions. 相似文献
13.
We report the formation of a new n=3 Ruddlesden-Popper (R-P) layered perovskite oxide, Ca2La2CuTi2O10 (I), in the metathesis reaction between NaLaTiO4 and Ca2CuO2Cl2 (n=1 R-P phases) at 700°C in air. Rietveld refinement of powder XRD data shows that I is isostructural with Sr4Ti3O10 (space group I4/mmm; a=3.8837(5), c=27.727(6) Å), consisting of triple perovskite CuTi2O10 sheets wherein Cu and Ti are ordered at the central and terminal octahedral sites, respectively. Magnetization data provide support for the presence of strong antiferromagnetically coupled CuO2 sheets in the structure. I is metastable decomposing at higher temperatures (∼950°C) to a mixture of perovskite-like CaLa2CuTi2O9 and CaO. Interestingly, the reaction between NaLaTiO4 and Sr2CuO2Cl2 follows a different metathesis route, 2NaLaTiO4+Sr2CuO2Cl2→La2CuO4+2SrTiO3+2NaCl, revealing multiplicity of reaction pathways for solid-state metathesis reactions. 相似文献
14.
Five new oxides, K3Ti5MO14, Rb3Ti5MO14 (M = Ta, Nb), and Tl3Ti5NbO14, have been synthesized. The structure of these oxides consists of octahedral layers similar to those observed for Na2Ti3O7 and held together by monovalent ions; the sheets consist of blocks of 2 × 3 edge-sharing octahedra, which are then joined to each other by the corners of the octahedra. The relative disposition of the layers is similar to that observed for Tl2Ti4O9. These oxides can be considered as the member n = 3 of a series of closely related structures with formula AnB2nO4n+2, where n indicates the number of octahedra which determines the width of the blocks of 2 × n octahedra. 相似文献
15.
Brendan J. Kennedy Qingdi Zhou Yoshika Kubota 《Journal of solid state chemistry》2008,181(6):1377-1386
Crystal structures of a series of bi-layered compounds ABi4Ti4O15 (A=Ca, Sr, Ba, Pb) have been investigated using a combination of synchrotron X-ray and neutron powder diffraction data. All four oxides adopt an orthorhombic structure at room temperature and the structures have been refined in space group A21am. This orthorhombic structure is a consequence of a combination of rotation of the TiO6, resulting from the less than optimal size of the A-type cation, and displacement of the Ti atoms towards the Bi2O2 layers. There is partial disorder of the Bi and A-type cations over two of the three available sites, which increases in the order Ca<Sr and Pb<Ba. 相似文献
16.
A new reduced potassium niobate (KNb4O6) of intergrowth type structure containing condensed Nb6O12 clusters has been found. The structure has been determined from HREM images. The atomic positions have been refined with the Rietveld technique using X-ray powder diffraction data. The space group of KNb4O6 is P4/mmm; Z = 1, and its unit cell parameters are a = 4.1393(1) and c = 8.2537(2). KNb4O6 consists of alternating slabs of KNbO3 (perovskite) and NbO (ordered deficient NaCl-type) both being a single unit thick. The structure is closely related to that of A2Nb5O9 (A = Ba, Sr). Both phases can be considered as members (n = 1 and 2 respectively) of a homologous series AnNb3+nO3+3n. Electron microscopy studies show the presence of defects, both as extra perovskite layers and missing NbO slabs, together with areas of more disordered intergrowth. The profile refinement and microanalysis of individual crystal fragments both indicate the structure to be niobium deficient according to the formula K1+x/2Nb4−xO6. 相似文献
17.
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
18.
A family of layered bismuth oxyhalides, LI0.5Bi1.5O2X and LIIBiO2X has been reinvestigated. Formation of X1-type Sillén compounds has been established for LI=Li, Na, LII=Ca, Sr, Ba, and X=Cl, Br, I, but the details of their crystal structures are different. While all LI0.5Bi1.5O2X, CaBiO2Br, and CaBiO2I adopt the disordered tetragonal Nd2O2Te structure, all compounds of LII=Sr and Ba are orthorhombic and isostructural to PbSbO2Cl, due to L/Bi cation ordering. Crystal structures have been determined for CaBiO2I, SrBiO2Br, SrBiO2I, and BaBiO2I. We discuss the factors which determine the occurrence and type of cation ordering in the quaternary bismuth and antimony X1-type oxyhalides. We also predict that more isostructural compounds can be prepared with antimony. 相似文献
19.
E. A. Tugova 《Russian Journal of General Chemistry》2016,86(11):2410-2417
Regularities of formation of complex aluminates with structure of P/RS intergrowth type phases in the Ln2O3–MO–Al2O3 systems (Ln = rare-earth element, M = Mg, Ca, Sr, Ba) have been considered. Systematization of the data on formation of complex compounds coexisting with one-layer phases in the Ln2O3–MO–Al2O3 systems and analysis of geometry criteria of LnMAlO4 stability is a promising approach to prediction of novel compounds with structure of Ruddlesden–Popper phase. 相似文献
20.
Chemical Vapour Transport of Ternary Oxides in the Systems Ca/Mo/O and Sr/Mo/O The chemical vapour transport behaviour of ternary phases in the Ca/Mo/O and Sr/Mo/O systems has been investigated using Cl2 as transport agent in a temperature gradient 1423 to 1323 K. MMoO4 (M= Ca, Sr) migrate in the above‐mentioned temperature gradient with rates of 0.1 to 0.2 mg/h. Starting from three phase mixtures crystals of the compounds MMo5O8 have been grown (migration rates: M = Ca 0.1 mg/h, M = Sr 0.01 mg/h). The observed transport behaviour is compared with predictions given by thermo dynamical model calculations and the influences of source composition and the moisture contents are described in detail. 相似文献