共查询到20条相似文献,搜索用时 15 毫秒
1.
Gunter Heymann 《Journal of solid state chemistry》2006,179(2):370-377
The new monoclinic cerium borogermanate Ce6(BO4)2Ge9O22 was synthesized under high-pressure and high-temperature conditions in a Walker-type multianvil apparatus at 10.5 GPa and 1200 °C. Ce6(BO4)2Ge9O22 crystallizes with two formula units in the space group P21/n with lattice parameters a=877.0(2), b=1079.4(2), c=1079.1(2) pm, and β=95.94(3)°. As the parameter pressure favours the formation of compounds with cations possessing high coordination numbers, it was possible to produce simultaneously BO4-tetrahedra and GeO6-octahedra in one and the same borogermanate for the first time. Furthermore, the cerium atoms show high coordination numbers (C.N.: 9 and 11), and one oxygen site bridges one boron and two germanium atoms (O[3]), which is observed here for the first time. Besides a structural discussion, temperature-dependent X-ray powder diffraction data are presented, demonstrating the metastable character of this high-pressure phase. 相似文献
2.
Accurate profile analysis of X-ray diffraction data was carried out to settle recent dispute on the symmetry and crystal structures of the double perovskite Ba2LaIrO6. Even through careful comparison of the full-width at half-maximum values, we found no evidence for Ba2LaIrO6 adopting either monoclinic (I2/m) or mixed rhombohedral and monoclinic (I2/m) structures at room temperature, becoming triclinic at below about 200 K. The correct space group is just at temperatures between 82 and 653 K. Furthermore, the phase transition does occur in Ba2LaIrO6, but the transition temperature is found to be much higher than the reported value. 相似文献
3.
Rodion V. Panin Nellie R. Khasanova Evgeny V. Antipov Walter Schnelle 《Journal of solid state chemistry》2007,180(5):1566-1574
NaPd3O4, Na2PdO3 and K3Pd2O4 have been prepared by solid-state reaction of Na2O2 or KO2 and PdO in sealed silica tubes. Crystal structures of the synthesized phases were refined by the Rietveld method from X-ray powder diffraction data. NaPd3O4 (space group Pm3¯n, a=5.64979(6) Å, Z=2) is isostructural to NaPt3O4. It consists of NaO8 cubes and PdO4 squares, corner linked into a three-dimensional framework where the planes of neighboring PdO4 squares are perpendicular to each other. Na2PdO3 (space group C2/c, a=5.3857(1) Å, b=9.3297(1) Å, c=10.8136(2) Å, β=99.437(2)°, Z=8) belongs to the Li2RuO3-structure type, being the layered variant of the NaCl structure, where the layers of octahedral interstices filled with Na+ and Pd4+ cations alternate with Na3 layers along the c-axis. Na2PdO3 exhibits a stacking disorder, detected by electron diffraction and Rietveld refinement. K3Pd2O4, prepared for the first time, crystallizes in the orthorhombic space group Cmcm (a=6.1751(6) Å, b=9.1772(12) Å, c=11.3402(12) Å, Z=4). Its structure is composed of planar PdO4 units connected via common edges to form parallel staggered PdO2 strips, where potassium atoms are located between them. Magnetic susceptibility measurements of K3Pd2O4 reveal a Curie-Weiss behavior in the temperature range above 80 K. 相似文献
4.
Tae-Soo You 《Journal of solid state chemistry》2010,183(6):1258-214
Reported are the synthesis and the structural characterization of four new polar intermetallic phases, which exist only with mixed alkaline-earth and rare-earth metal cations in narrow homogeneity ranges. (Sr1-xCax)5In3Ge6 and (Eu1-xYbx)5In3Ge6 (x≈0.7) crystallize in the orthorhombic space group Pnma with two formula units per unit cell (own structure type, Pearson symbol oP56). The lattice parameters are as follows: a=13.109(3)-13.266(3) Å, b=4.4089(9)-4.4703(12) Å, and c=23.316(5)-23.557(6) Å. (Sr1-xCax)3In2Ge4 and (Sr1-xYbx)3In2Ge4 (x≈0.4-0.5) adopt another novel monoclinic structure-type (space group C2/m, Z=4, Pearson symbol mS36) with lattice parameters in the range a=19.978(2)-20.202(2) Å, b=4.5287(5)-4.5664(5) Å, c=10.3295(12)-10.3447(10) Å, and β=98.214(2)-98.470(2)°, depending on the metal cations and their ratio. The polyanionic sub-structures in both cases are based on chains of InGe4 corner-shared tetrahedra. The A5In3Ge6 structure (A=Sr/Ca or Sr/Yb) also features Ge4 tetramers, and isolated In atoms in nearly square-planar environment, while the A3In2Ge4 structure (A=Sr/Ca or Eu/Yb) contains zig-zag chains of In and Ge strings with intricate topology of cis- and trans-bonds. The experimental results have been complemented by tight-binding linear muffin-tin orbital (LMTO) band structure calculations. 相似文献
5.
Ying-Zhi Cheng Xiu-Yu Sun Xiao-Ling Xiao Xiang-Feng Liu Li Xue Zhong-Bo Hu 《中国化学快报》2017,28(7):1600-1606
Crystal structures and thermal expansion properties of Yb_(2-x)Fe_xMo_3O_(12)(x=0.0,0.6,1.0,1.1,1.4) solid solutions have been studied by X-ray powder diffraction(XRPD) at different temperatures.Rietveld analysis of the XRPD data shows that Yb_(2-x)Fe_xMo_3O_(12) solid solutions adopt orthorhombic structure and have variable thermal expansion coefficients controlled by the ratio of Yb~(3+) to Fe~(3+).Yb_2Mo_3O_(12) shows anisotropic negative thermal expansion property,induced by the reductions in average Yb-O-Mo angle and average apparent Mo2-O bond length with increasing temperatures.As more Yb~(3+) substituted by Fe~(3+),the linear thermal expansion coefficients of Yb_(2-x)Fe_xMo_3O_(12) increase from negative to positive.A near-zero thermal expansion coefficient of 0.55×10~(-6)K~(-1) for Yb_(0.6)Fe_(1.4)Mo_3O_(12) is observed in the temperature range of 573-873 K 相似文献
6.
Ivan V. Ogorodnyk Igor V. Zatovsky Vyacheslav N. Baumer 《Journal of solid state chemistry》2006,179(12):3681-3687
The single crystals of caesium magnesium titanium (IV) tri-oxo-tetrakis-diphosphate bis-monophosphate, Cs3.70Mg0.60Ti2.78(TiO)3(P2O7)4(PO4)2, crystallize in sp. gr. P-1 (No. 2) with cell parameters a=6.3245(4), b=9.5470(4), c=15.1892(9) Å, α=72.760(4), β=85.689(5), γ=73.717(4), z=1. The titled compound possesses a three-dimensional tunnel structure built by the corner-sharing of distorted [TiO6] octahedra, [Ti2O11] bioctahedra, [PO4] monophosphate and [P2O7] pyrophosphate groups. The Cs+ cations are located in the tunnels. The partial substitution of Ti positions with Mg atoms is observed. The negative charge of the framework is balanced by Cs cations and Mg atoms leading to pronounced concurrency and orientation disorder in the [P2O7] groups, which coordinate both. 相似文献
7.
Junji Awaka Norihito Kijima Hiroshi Hayakawa Junji Akimoto 《Journal of solid state chemistry》2009,182(8):2046-2052
We have successfully synthesized a high-purity polycrystalline sample of tetragonal Li7La3Zr2O12. Single crystals have been also grown by a flux method. The single-crystal X-ray diffraction analysis verifies that tetragonal Li7La3Zr2O12 has the garnet-related type structure with a space group of I41/acd (no. 142). The lattice constants are a=13.134(4) Å and c=12.663(8) Å. The garnet-type framework structure is composed of two types of dodecahedral LaO8 and octahedral ZrO6. Li atoms occupy three crystallographic sites in the interstices of this framework structure, where Li(1), Li(2), and Li(3) atoms are located at the tetrahedral 8a site and the distorted octahedral 16f and 32g sites, respectively. The structure is also investigated by the Rietveld method with X-ray and neutron powder diffraction data. These diffraction patterns are identified as the tetragonal Li7La3Zr2O12 structure determined from the single-crystal data. The present tetragonal Li7La3Zr2O12 sample exhibits a bulk Li-ion conductivity of σb=1.63×10−6 S cm−1 and grain-boundary Li-ion conductivity of σgb=5.59×10−7 S cm−1 at 300 K. The activation energy is estimated to be Ea=0.54 eV in the temperature range of 300–560 K. 相似文献
8.
Vladimir G. Zubkov Ivan I. Leonidov Alexander P. Tyutyunnik Ludmila L. Surat Marina A. Melkozerova Elena V. Zabolotskaya Dina G. Kellerman 《Journal of solid state chemistry》2010,183(5):1186-1346
The crystal structure of the promising optical materials Ln2M2+Ge4O12, where Ln=rare-earth element or Y; M=Ca, Mn, Zn and their solid solutions has been studied in detail. The tendency of rare-earth elements to occupy six- or eight-coordinated sites upon iso- and heterovalent substitution has been studied for the Y2−xErxCaGe4O12 (x=0-2), Y2−2xCexCa1+xGe4O12 (x=0-1), Y2Ca1−xMnxGe4O12 (x=0-1) and Y2−xPrxMnGe4O12 (x=0-0.5) solid solutions. A complex heterovalent state of Eu and Mn in Eu2MnGe4O12 has been found. 相似文献
9.
The germanate compound Cu2Sc2Ge4O13 has been synthesized by solid-state ceramic sintering techniques between 1173 and 1423 K. The structure was solved from single-crystal data by Patterson methods. The title compound is monoclinic, a=12.336(2) Å, b=8.7034(9) Å, c=4.8883(8) Å, β=95.74(2), space group P21/m, Z=4. The compound is isotypic with Cu2Fe2Ge4O13, described very recently. The structure consists of crankshaft-like chains of edge-sharing ScO6 octahedra running parallel to the crystallographic b-axis. These chains are linked laterally by [Cu2O6]8− dimers forming a sheet of metal-oxygen-polyhedra within the a-b plane. These sheets are separated along the c-axis by [Ge4O13]10− units. Cooling to 100 K does not alter the crystallographic symmetry of Cu2Sc2Ge4O13. While the b, c lattice parameter and the unit cell volume show a positive linear thermal expansion (α=6.4(2)×10−6, 5.0(2)×10−6 and 8.3(2)×10−6 K−1 respectively), the a lattice parameter exhibits a negative thermal expansion (α=−3.0(2)×10−6 K−1) for the complete T-range investigated. This negative thermal expansion of a is mainly due to the increase of the Cu-Cu interatomic distance, which is along the a-axis. Average bond lengths remain almost constant between 100 and 298 K, whereas individual ones partly show both significant shortages and lengthening. 相似文献
10.
The crystal structure of metastable Li2Si3O7 was determined from single crystal X-ray diffraction data. The orthorhombic crystals were found to adopt space group Pmca with unit cell parameters of , and . The content of the cell is Z=4. The obtained structural model was refined to a R-value of 0.035. The structure exhibits silicate sheets, which can be classified as [Si6O14] using the silicate nomenclature of Liebau. The layers are build up from zweier single chains running parallel to c. Raman spectra are presented and compared with other silicates. Furthermore, the structure is discussed versus Na2Si3O7. 相似文献
11.
Yang Zhou Yanqiang Li Qingran Ding Youchao Liu Yangxin Chen Xitao Liu Xiaoying Huang Lina Li Sangen Zhao Junhua Luo 《中国化学快报》2021,32(1):263-265
Two fluoride sulfates,K2Mn3(SO4)3F2·4H2O(Ⅰ) and Rb2Mn3(SO4)3F2·2H2O (Ⅱ) are obtained by water solution method.Single-crystal X-ray diffraction analysis indicated that they crystallize in space groups of Cmc21.Their structures feature a pseudo-KTP structure consisting of interconnecting[Mn3(SO4)3F2(H2O)2]∞ layers,which are further packing along the a axis with alkali metal cations balancing the charges.The structure relationships between the two compounds are discussed.Secondharmonic generation measurements manifest that Ⅰ and Ⅱ have similar second-harmonic generation responses of about 0.2 and 0.25 times that of KH2PO4. 相似文献
12.
The complex perovskite BiMn7O12 occurs with two polymorphic structures, cubic and monoclinic. Currently their crystal structures are investigated with high-resolution synchrotron powder X-ray diffraction at room temperature. Rietveld analysis reveals unusual behavior for, respectively, the oxygen and bismuth atoms in the monoclinic and cubic phases. Bond valence calculations indicate that all the Mn atoms in both the phases are in trivalent state. Possible roles of the 6s2 lone-pair electrons of Bi3+ in BiMn7O12 are discussed in comparison with the LaMn7O12 phase that is isomorphic to monoclinic BiMn7O12. Multiple roles of the lone-pair electrons are revealed, causing (i) A-site cation deficiency, (ii) octahedral tilting, (iii) A-site cation displacement, and (iv) Mn3+ Jahn-Teller (JT) distortion. Relationships between the monoclinic and cubic phases are discussed with emphasis on the MnO2 and MnO6 local structural aspects. All Mn atoms in the monoclinic polymorph have distorted coordination consistent with JT-active Mn(III) high spin, whereas for the cubic polymorph, the B-site Mn atoms show regular octahedral coordination. 相似文献
13.
A tin(II) squarate Sn2O(C4O4)(H2O) was synthesized by hydrothermal technique. It crystallizes in the monoclinic system, space group C2/m (no. 12) with lattice parameters a=12.7380(9) Å, b=7.9000(3) Å, c=8.3490(5) Å, β=121.975(3)°, V=712.69(7) Å3, Z=4. The crystal structure determined with an R=0.042 factor, consists of [(Sn4O10)(H2O)2] units connected from one another in the [101] and [010] directions via squarate groups to form layers separated by Sn(II) lone pairs. This compound presents the same remarkable structural arrangement as observed in the tin-oxo-fluoride Sn2[Sn2O2F4] inorganic compound with Sn(II) lone pairs E(1) and E(2) concentrated in large rectangular-shape tunnels running along [001] direction. 相似文献
14.
Alexei A. Belik Qingzhen Huang Jeffrey W. Lynn 《Journal of solid state chemistry》2008,181(9):2292-2297
The crystal and magnetic structures of SrFe2+2(PO4)2 have been determined by neutron powder diffraction data at low temperatures (space group P21/c (no. 14); Z=4; a=9.35417(13) Å, b=6.83808(10) Å, c=10.51899(15) Å, and β=109.5147(7)° at 15 K). Two magnetic phase transitions were found at T1=7.4 K (first-order phase transition) and T2=11.4 K (second-order phase transition). The transition at T2 was hardly detectable by dc and ac magnetization measurements, and a small anomaly was observed by specific heat measurements. At T1, strong anomalies were found by dc and ac magnetization and specific heat. The structure of SrFe2(PO4)2 consists of linear four-spin cluster units, Fe2-Fe1-Fe1-Fe2. Below T1, the propagation vector of the magnetic structure is k=[0,0,0]. The magnetic moments of the inner Fe1-Fe1 atoms of the four-spin cluster unit are ferromagnetically coupled. The magnetic moment of the outer Fe2 atom is also ferromagnetically coupled with that of the Fe1 atom but with spin canting. The four-spin cluster units form ferromagnetic layers parallel to the [−101] plane, while these layers are stacked antiferromagnetically in the [−101] direction. Spin canting of the outer Fe2 atoms provides a weak ferromagnetic moment of about 1 μB along the b-axis. The refined magnetic moments at 3.5 K are 4.09 μB for Fe1 and 4.07 μB for Fe2. Between T1 and T2, a few weak magnetic reflections were observed probably due to incommensurate magnetic order. 相似文献
15.
A new cesium uranyl niobate, Cs9[(UO2)8O4(NbO5)(Nb2O8)2] or Cs9U8Nb5O41 has been synthesized by high-temperature solid-state reaction, using a mixture of U3O8, Cs2CO3 and Nb2O5. Single crystals were obtained by incongruent melting of a starting mixture with metallic ratio=Cs/U/Nb=1/1/1. The crystal structure of the title compound was determined from single crystal X-ray diffraction data, and solved in the monoclinic system with the following crystallographic data: a=16.729(2) Å, b=14.933(2) Å, c=20.155(2) Å β=110.59(1)°, P21/c space group and Z=4. The crystal structure was refined to agreement factors R1=0.049 and wR2=0.089, calculated for 4660 unique observed reflections with I?2σ(I), collected on a BRUKER AXS diffractometer with MoKα radiation and a CCD detector.In this structure the UO7 uranyl pentagonal bipyramids are connected by sharing edges and corners to form a uranyl layer corresponding to a new anion-sheet topology, and creating triangular, rectangular and square vacant sites. The two last sites are occupied by Nb2O8 entities and NbO5 square pyramids, respectively, to form infinite uranyl niobate sheets stacking along the [010] direction. The Nb2O8 entities result from two edge-shared NbO5 square pyramids. The Cs+ cations are localized between layers and ensured the cohesion of the structure.The cesium cation mobility between the uranyl niobate sheets was studied by electrical measurements. The conductivity obeys the Arrhenius law in all the studied temperature domains. The observed low conductivity values with high activation energy may be explained by the strong connection of the Cs+ cations to the infinite uranyl niobate layers and by the high density of these cations in the interlayer space without vacant site.Infrared spectroscopy investigated at room temperature in the frequency range 400-4000 cm−1, showed some characteristic bands of uranyl ion and niobium polyhedra. 相似文献
16.
Digamber G. Porob 《Journal of solid state chemistry》2004,177(12):4535-4541
Two new compounds Ca0.5Bi3V2O10 and Sr0.5Bi3V2O10 have been synthesized in the ternary system: MO-Bi2O3-V2O5 system (M=M2+). The crystal structure of Sr0.5Bi3V2O10 has been determined from single crystal X-ray diffraction data, space group and Z=2, with cell parameters a=7.1453(3) Å, b=7.8921(3) Å, c=9.3297(3) Å, α=106.444(2)°, β=94.088(2)°, γ=112.445(2)°, V=456.72(4) Å3. Ca0.5Bi3V2O10 is isostructural with Sr0.5Bi3V2O10, with, a=7.0810(2) Å, b=7.8447(2) Å, c=9.3607(2) Å, α=106.202(1)°, β=94.572(1)°, γ=112.659(1)°, V=450.38(2) Å3 and its structure has been refined by Rietveld method using powder X-ray data. The crystal structure consists of infinite chains of (Bi2O2) along c-axis formed by linkage of BiO8 and BiO6 polyhedra interconnected by MO8 polyhedra forming 2D layers in ac plane. The vanadate tetrahedra are sandwiched between these layers. Conductivity measurements give a maximum conductivity value of 4.54×10−5 and 3.63×10−5 S cm−1 for Ca0.5Bi3V2O10 and Sr0.5Bi3V2O10, respectively at 725 °C. 相似文献
17.
Bi2O3-MoO3 system shows a large panoply of phases depending on Bi/Mo ratio, among them, the low temperature phases of the homologous series Bi2(n+2)MonO6(n+1) with n=3, 4, 5 and 6. They exhibit, alike most of the phases of this system, strong fluorite sub-network. Nevertheless, a multitechnique approach has been followed in order to solve the crystal structure of the n=3 member, i.e. Bi10Mo3O24. From ab initio indexing X-ray powder pattern cell parameters were derived. It belongs to the monoclinic system, space group C2, with cell parameters: a=23.7282(2) Å, b=5.64906(6) Å, c=8.68173(9) Å, β=95.8668(7)° with Z=2. The matrix relating this cell with the fluorite one is 4 0 1/0 1 0/ 0 and a cationic localization was derived. HRTEM allowed the cationic Bi and Mo order to be modified and specified, as well as to build up a full structural ab initio model on the basis of crystal chemistry considerations. Simultaneous Rietveld refinement of multipattern X-ray and neutron powder diffraction data taking advantage of the neutron scattering length for O location have been performed. The goodness of the model was ascertained by low reliability factors, weighted Rb=4.97% and Rf=3.21%. This complex Bi10Mo3O24 structure, with 5Bi, 2Mo and 13O in different crystallographic positions of the asymmetric unit, shows good agreement between observed and calculated patterns within the data resolution. Moreover, the determination of this structure sets the basis for the crystallographic characterization of the complete family Bi2(n+2)MonO6(n+1), whose guidelines are also evidenced in this paper. 相似文献
18.
Najoua Ouerfelli Daniele Mazza Mohamed Faouzi Zid 《Journal of solid state chemistry》2007,180(4):1224-1229
A new solid solution TlFe0.22Al0.78As2O7 has been synthesized by a solid-state reaction. The structure of the title compound has been determined from a single-crystal X-ray diffraction and refined to final values of the reliability factors: R(F2)=0.030 and wR(F2)=0.081 for 1343 independent reflections with I>2σ(I). It crystallizes in the triclinic space group P-1, with a=6.296(2) Å, b=6.397(2) Å, c=8.242(2) Å, α=96.74(2)°, β=103.78(2)°, γ=102.99(3)°, V=309.0(2) Å3 and Z=2. The structure can be described as a three-dimensional framework containing (Fe/Al)O6 octahedra connected through As2O7 groups. The metallic units and diarsenate groups share oxygen corners to form a three-dimensional framework with interconnected tunnels parallel to the a, b and c directions, where Tl+ cations are located. The ionic conductivity measurements are performed on pellets of the polycrystalline powder. At 683 K, The conductivity value is 5.23×10−6 S cm−1 and the ionic jump activation energy is 0.656 eV. The bond valence analysis reveals that the ionic conductivity is ensured by Tl+ along the [001] direction. 相似文献
19.
The crystal structure of Ca5Te3O14 at room temperature was studied by the Rietveld method using combined X-ray and neutron powder diffraction data. The compound crystallizes in the space group Cmca with the lattice parameters a=10.4268(2) Å, b=10.3908(2) Å and c=10.4702(2) Å. The structure of Ca5Te3O14 is chiolite-like and consists of a framework of corner-linked TeO6 octahedral layers in which a linear TeO2 group of every fourth octahedron is substituted by a Ca atom. This type of structure was previously observed in BaSr4U3O14. The relationship between the chiolite-like structure and the fluorite structure is discussed. 相似文献
20.
M.G. Krzhizhanovskaya R.S. Bubnova M.S. Kozin S.K. Filatov 《Journal of solid state chemistry》2009,182(5):1260-1264
A new compound, SrBi2B4O10, has been grown by cooling a melt with the stoichiometric composition. It is triclinic, P−1, a=6.819(1), b=6.856(1), c=9.812(2) Å, α=96.09(1), β=109.11(1), γ=101.94(1)°, V=416.5(1) Å3, Z=2. The crystal structure of the compound has been solved by direct methods and refined to R1=0.050 (wR2=0.128). The structure contains Bi-O pseudolayers build up from Bi-O chains involving oxocentred OBi3 triangles. Sr atoms and [B4O9]6− isolated anions (4B:3Δ□:<2Δ□>Δ) are located between the Bi-O packages.The thermal treatment as well as DSC experiment showed that the compound melts above 800 °C presumably according to the peritectic reaction: SrBi2B4O10 ↔ SrB2O4+SrB4O7+ Liquid. According to high-temperature X-ray powder diffraction study thermal expansion of SrBi2B4O10 structure is anisotropic (α11=13, α22=9, α33=2, αV=24×10−6 °C−1). 相似文献