共查询到20条相似文献,搜索用时 46 毫秒
1.
Annette P Richard 《Journal of solid state chemistry》2004,177(8):2740-2748
Subsolidus phase relationships in the In2O3-WO3 system at 800-1400°C were investigated using X-ray diffraction. Two binary-oxide phases—In6WO12 and In2(WO4)3—were found to be stable over the range 800-1200°C. Heating the binary-oxide phases above 1200°C resulted in the preferential volatilization of WO3. Rietveld refinement was performed on three structures using X-ray diffraction data from nominally phase-pure In6WO12 at room temperature and from nominally phase-pure In2(WO4)3 at 225°C and 310°C. The indium-rich phase, In6WO12, is rhombohedral, space group (rhombohedral), with Z=1, a=6.22390(4) Å, α=99.0338(2)° [hexagonal axes: aH=9.48298(6) Å, c=8.94276(6) Å, aH/c=0.9430(9)]. In6WO12 can be viewed as an anion-deficient fluorite structure in which 1/7 of the fluorite anion sites are vacant. Indium tungstate, In2(WO4)3, undergoes a monoclinic-orthorhombic transition around 250°C. The high-temperature polymorph is orthorhombic, space group Pnca, with a=9.7126(5) Å, b=13.3824(7) Å, c=9.6141(5) Å, and Z=4. The low-temperature polymorph is monoclinic, space group P21/a, with a=16.406(2) Å, b=9.9663(1) Å, c=19.099(2) Å, β=125.411(2)°, and Z=8. The structures of the two In2(WO4)3 polymorphs are similar, consisting of a network of corner sharing InO6 octahedra and WO4 tetrahedra. 相似文献
2.
Matic Lozinšek Evgeny Goreshnik Anton Meden Gašper Tav?ar 《Journal of solid state chemistry》2009,182(10):2897-2903
In the system BaF2/BF3/PF5/anhydrous hydrogen fluoride (aHF) a compound Ba(BF4)(PF6) was isolated and characterized by Raman spectroscopy and X-ray diffraction on the single crystal. Ba(BF4)(PF6) crystallizes in a hexagonal space group with a=10.2251(4) Å, c=6.1535(4) Å, V=557.17(5) Å3 at 200 K, and Z=3. Both crystallographically independent Ba atoms possess coordination polyhedra in the shape of tri-capped trigonal prisms, which include F atoms from BF4− and PF6− anions. In the analogous system with AsF5 instead of PF5 the compound Ba(BF4)(AsF6) was isolated and characterized. It crystallizes in an orthorhombic Pnma space group with a=10.415(2) Å, b=6.325(3) Å, c=11.8297(17) Å, V=779.3(4) Å3 at 200 K, and Z=4. The coordination around Ba atom is in the shape of slightly distorted tri-capped trigonal prism which includes five F atoms from AsF6− and four F atoms from BF4− anions. When the system BaF2/BF3/AsF5/aHF is made basic with an extra addition of BaF2, the compound Ba2(BF4)2(AsF6)(H3F4) was obtained. It crystallizes in a hexagonal P63/mmc space group with a=6.8709(9) Å, c=17.327(8) Å, V=708.4(4) Å3 at 200 K, and Z=2. The barium environment in the shape of tetra-capped distorted trigonal prism involves 10 F atoms from four BF4−, three AsF6− and three H3F4− anions. All F atoms, except the central atom in H3F4 moiety, act as μ2-bridges yielding a complex 3-D structural network. 相似文献
3.
Ulrike Troitzsch Andrew G. Christy David J. Ellis 《Journal of solid state chemistry》2007,180(10):2885-2895
We report a new zirconium titanate compound (Zr,Ti)O2 with 27.5-35 mol% titania (TiO2) formed from the oxides at 35-38 kbar, 1400-1500 °C. Crystal structure investigations at atmospheric conditions with powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed a monoclinic structure related to that of M-fergusonite (beta). Unit-cell dimensions (from 27.5 to 35 mol% TiO2): a=7.267(20)-7.340(2) Å, b=10.435(3)-10.429(1) Å, c=5.023(11)-5.040(1) Å, β=136.45(12)-137.55(1)°, V=262.44(92)-260.40(12) Å3, Z=4. Rietveld refinement (RF=1.55) of a sample with 32.8 mol% TiO2 indicates that site A is 8-fold coordinated, mostly occupied by Zr, while site B has 6-fold average coordination, occupied by Ti and Zr. Site B is at least partly ordered, as indicated by superstructure reflections 0 0 1 and −2 0 1 detected with TEM, reducing the space group from C2/c to C2. Pronounced streaking of selected diffraction spots is linked to the boundaries of lamellar domains in twin orientation, with twin planes either (200) or (20−2). Adjacent lamellae differ slightly in composition, causing subtle asymmetry of the twin diffraction patterns. 相似文献
4.
Three novel metal polyphosphides, α-SrP3, BaP8, and LaP5, were prepared in BN crucibles by the reaction of the respective stoichiometric mixtures under a high pressure of 3 GPa at 950-1000°C. Their crystal structures were determined from single-crystal X-ray data (α-SrP3: space group C2/m, a=9.199(6) Å, b=7.288(3) Å, c=5.690(3) Å, β=113.45(4)°, Z=4, R1/wR2=0.0684/0.1180 for 471 observed reflections and 22 variables; BaP8: space group P−1, a=6.762(2) Å, b=7.233(2) Å, c=8.567(2) Å, α=86.32(2)°, β=84.31(2)°, γ=70.40(2)°, Z=2, R1/wR2=0.0476/0.1255 for 2702 observed reflections and 82 variables; LaP5: space group P21/m, a=4.885(1) Å, b=9.673(3) Å, c=5.577(2) Å, β=105.32(2)°, Z=2, R1/wR2=0.0391/0.1034 for 1272 observed reflections and 31 variables). α-SrP3 is isostructural with SrAs3 and the crystal structure consists of two-dimensional puckered polyanionic layers ∞2[P3]2− that stack along the c-axis yielding channels occupied by Sr2+ counterions. BaP8 crystallizes in a new structure type which contains a three-dimensional infinite polyanionic framework ∞3[P3]2−, with large channels hosting the barium cations. LaP5 is a layered compound containing ∞2[P5]3− polyanionic layers separated by La3+ ions. All three compounds exhibit expected diamagnetic behaviors. 相似文献
5.
Crystal structure of LiB3O5 (a framework of [B3O5]− rings and Li atoms located in interspaces) was refined at high temperatures using single-crystal X-ray diffraction, MoKα-radiation, anharmonic approximation, orthorhombic; Pna21; Z=4; 20 °C (a=8.444, b=7.378, c=5.146 Å, 1411 F(hkl), R=0.022); 227 °C (a=8.616, b=7.433, c=5.063 Å, 1336 F(hkl), R=0.026), 377 °C (a=8.746, b=7.480, c=5.013 Å, 1193 F(hkl), R=0.035). A high mobility of Li atoms and their highly asymmetric vibrations are revealed. Ellipsoid of Li thermal vibrations is oviform. Li is shifted on heating to 0.26 Å mainly along a-axis causing high thermal expansion in this direction; Li temperature factors are multiplied by 4 on heating. Rigid boron-oxygen groups in LiB3O5 remain practically stable on heating similar to α-Na2B8O13 and α-CsB5O8. At the same time these groups rotate relative to each other like hinges leading to extremely anisotropic thermal expansion (αa=101, αb=31, αc=−71, αv=60×10−6 °C−1, 20-530 °C, HTXRPD data). 相似文献
6.
The compound NaAlF4 has been obtained in the form of thin fibrous crystals or fine colorless powder by condensation at 18 °C of vapors arising over chiolite Na5Al3F14 or NaCaAlF6, heated up to 800 °C. Thermal stability has been investigated by the methods of thermal analysis and high temperature X-ray diffraction. When heated in air, NaAlF4 is stable up to 390-400 °C, then there is an exothermal solid state decay into Na5Al3F14(s) and AlF3(s). At higher temperature Na5Al3F14(s) decays into Na3AlF6(s) and NaAlF4(g). The crystal structure (space group Cmcm, a=3.6124(1) Å, b=14.9469(7) Å, c=5.2617(3) Å, V=284.10 Å3) has been determined by X-ray powder diffraction method. In the crystal structure of NaAlF4 the octahedrons [AlF6] are joined through vertices and form corrugated layers, sodium ion layers being located between them. The distances between the atoms of Al-F are in the range 1.791-1.814 Å, and those for Na…F are in the range 2.297-2.439 Å. In spite of limited thermal stability of the crystal form, the compound NaAlF4 is the main component of the gas mixture over solid and molten salts in the ternary system NaF-AlF3-CaF2 and participates in chemical transformations between the phases at high temperature. 相似文献
7.
Synthesis and crystal structure of Bi6.4Pb0.6P2O15.2: A new polymorph in the series Bi6+xM1−xP2O15+y
Bi6.4Pb0.6P2O15.2 is a polymorph of structures with the general stoichiometry Bi6+xM1−xP2O15+y. However, unlike previously published structures that consist of layers formed by edge sharing OBi4 tetrahedra bridged by PO4 and TO6 (T=transition metal) tetrahedra and octahedra the title compound's structure is more complex. It is monoclinic, C2, a=19.4698(4) Å, b=11.3692(3) Å, c=16.3809(5) Å, β=101.167(1)°, Z=10. Single-crystal X-ray diffraction data were refined by least squares on F2 converging to R1=0.0387, wR2=0.0836 for 7023 intensities. The crystal twins by mirror reflection across (001) as the twin plane and twin component 1 equals 0.74(1). Oxygen ions are in tetrahedral coordination to four metal ions and the O(BiPb)4 units share corners to form layers that are part of the three-dimensional framework. Eight oxygen ions form a cube around the two crystallographically independent Pb ions. Pb-O bond lengths vary from 2.265(14) to 2.869(14) Å. Pairs of such cubes share an edge to form a Pb3O20 unit. The two oxygen ions from the unshared edges are part of irregular Bi polyhedra. Other oxygen ions of Bi polyhedra are part only of O(BiPb)4 units, and some oxygen ions of the polyhedra are also part of PO4 tetrahedra. One, two, three and or four PO4 moieties are connected to the Bi polyhedra. Bi-O bond lengths ?3.1 Å vary from 2.090(12) to 3.07(3) Å. The articulations of Pb cubes, Bi polyhedra and PO4 tetrahedra link into the three-dimensional structure. 相似文献
8.
Stanislav Filatov Yurij Shepelev Natalia Sennova Yury F. Kargin 《Journal of solid state chemistry》2004,177(2):515-522
The paper presents a new data on the crystal structure, thermal expansion and IR spectra of Bi3B5O12. The Bi3B5O12 single crystals were grown from the melt of the same stoichiometry by Czochralski technique. The crystal structure of Bi3B5O12 was refined in anisotropic approximation using single-crystal X-ray diffraction data. It is orthorhombic, Pnma, a=6.530(4), b=7.726(5), c=18.578(5) Å, V=937.2(5) Å3, Z=4, R=3.45%. Bi3+ atoms have irregular coordination polyhedra, Bi(1)O6 (d(B-O)=2.09-2.75 Å) and Bi(2)O7 (d(B-O)=2.108-2.804 Å). Taking into account the shortest bonds only, these polyhedra are considered here as trigonal Bi(1)O3 (2.09-2.20 Å) and tetragonal Bi(2)O4 (2.108-2.331 Å) irregular pyramids with Bi atoms in the tops of both pyramids. The BiO4 polyhedra form zigzag chains along b-axis. These chains alternate with isolated anions [B2IVB3IIIO11]7− through the common oxygen atoms to form thick layers extended in ab plane. A perfect cleavage of the compound corresponds to these layers and an imperfect one is parallel to the Bi-O chains. The Bi3B5O12 thermal expansion is sharply anisotropic (α11≈α22=12, α33=3×10−6 °C−1) likely due to a straightening of the flexible zigzag chains along b-axis and decreasing of their zigzag along c-axis. Thus the properties like cleavage and thermal expansion correlate to these chains. 相似文献
9.
G.B. Song C.Q. Han J.K. Liang Q.L. Liu F.S. Liu G.H. Rao 《Journal of solid state chemistry》2004,177(7):2394-2403
The subsolidus phase relations of the PrOx-CaO-CuO pseudo-ternary system sintered at 950-1000°C have been investigated by X-ray powder diffraction. In this system, there exist one compound Ca10Pr4Cu24O41, one Ca2Pr2Cu5O10-based solid solution, seven three-phase regions and two two-phase regions. The crystal structures of Ca10Pr4Cu24O41 and Ca2Pr2Cu5O10-based solid solution have been determined. Compound Ca10Pr4Cu24O41 crystallizes in an orthorhombic cell with space group D2h20−Cccm, Z=4. Its lattice parameters are a=11.278(2) Å, b=12.448(3) Å and c=27.486(8) Å. The crystal structure of Ca2Pr2Cu5O10-based solid solution is an incommensurate phase based on the orthorhombic NaCuO2 type subcell. The lattice parameters of the subcell of the Ca2.4Pr1.6Cu5O10 are a0=2.8246(7) Å, b0=6.3693(5) Å, c0=10.679(1) Å, and those of the orthorhombic superstructure are with a=5a0, b=b0, c=5c0. The Ca2.4Pr1.6Cu5O10 structure can also be determined by using a monoclinic supercell with space group C2h5−P21/c, Z=4, a=5a0, b=b0, and β=104.79(1)° or 136.60(1)°, V=5a0b0c0. 相似文献
10.
The two new compounds, Sr4Cu3(AsO4)2(AsO3OH)4·3H2O (1) and Ba2Cu4(AsO4)2(AsO3OH)3(2), were synthesized under hydrothermal conditions. They represent previously unknown structure types and are the first compounds synthesized in the systems SrO/BaO-CuO-As2O5-H2O. Their crystal structures were determined by single-crystal X-ray diffraction [space group C2/c, a=18.536(4) Å, b=5.179(1) Å, c=24.898(5) Å, β=93.67(3)°, V=2344.0(8) Å3, Z=4 for 1; space group P42/n, a=7.775(1) Å, c=13.698(3) Å, V=828.1(2) Å3, Z=2 for 2]. The crystal structure of 1 is related to a group of compounds formed by Cu2+-(XO4)3− layers (X=P5+, As5+) linked by M cations (M=alkali, alkaline earth, Pb2+, or Ag+) and partly by hydrogen bonds. In 1, worth mentioning is the very short hydrogen bond length, D···A=2.477(3) Å. It is one of the examples of extremely short hydrogen bonds, where the donor and acceptor are crystallographically different. Compound 2 represents a layered structure consisting of Cu2O8 centrosymmetric dimers crosslinked by As1φ4 tetrahedra, where φ is O or OH, which are interconnected by Ba, As2 and hydrogen bonds to form a three-dimensional network. The layers are formed by Cu2O8 centrosymmetric dimers of CuO5 edge-sharing polyhedra, crosslinked by As1O4 tetrahedra. Vibrational spectra (FTIR and Raman) of both compounds are described. The spectroscopic manifestation of the very short hydrogen bond in 1, and ABC-like spectra in 2 were discussed. 相似文献
11.
Dmitry V. Peryshkov 《Journal of fluorine chemistry》2010,131(11):1252-1256
The anhydrous salt K2B12F12 crystallized from aqueous solution and its structure was determined by single crystal X-ray diffraction. The Ni2In-type structure it exhibits is rare for an A2X ionic compound at 25 °C and 1 atm., consisting of an expanded hexagonal close-packed array of B12F122− centroids (cent?cent distances: 7.204-8.236 Å) with half of the K+ ions filling all of the Oh holes and half of the K+ ions filling all of the D3h trigonal holes in the close-packed layers that are midway between two “empty” Td holes. The structure is also unusual in that the bond-valence sum for the K+ ions in Oh holes is less than or equal to 0.73 (the bond-valence sum for the other type of K+ ion is 1.16). A variation of the Ni2In structure is exhibited by the previously published monohydrate Cs2(H2O)B12F12, for which an improved structure is also reported here. For K2B12F12: monoclinic, C2/c, a = 8.2072(8), b = 14.2818(7), c = 11.3441(9) Å, β = 92.832(5)°, Z = 4, T = 120(2) K. For Cs2(H2O)B12F12: orthorhombic, P212121, a = 9.7475(4), b = 10.2579(4), c = 15.0549(5) Å, Z = 4, T = 110(1) K. 相似文献
12.
Synthesis, crystal structures, magnetic and electric transport properties of Eu11InSb9 and Yb11InSb9
Sheng-qing Xia Svilen Bobev Arif Ozbay Veronika Fritsch 《Journal of solid state chemistry》2007,180(7):2088-2094
Two new rare-earth metal containing Zintl phases, Eu11InSb9 and Yb11InSb9 have been synthesized by reactions of the corresponding elements in molten In metal to serve as a self-flux. Their crystal structures have been determined by single crystal X-ray diffraction—both compounds are isostructural and crystallize in the orthorhombic space group Iba2 (No. 45), Z=4 with unit cell parameters a=12.224(2) Å, b=12.874(2) Å, c=17.315(3) Å for Eu11InSb9, and a=11.7886(11) Å, b=12.4151(12) Å, c=16.6743(15) Å for Yb11InSb9, respectively (Ca11InSb9-type, Pearson's code oI84). Both structures can be rationalized using the classic Zintl rules, and are best described in terms of discrete In-centered tetrahedra of Sb, [InSb4]9−, isolated Sb dimers, [Sb2]4−, and isolated Sb anions, Sb3−. These anionic species are separated by Eu2+ and Yb2+ cations, which occupy the empty space between them and counterbalance the formal charges. Temperature-dependent magnetic susceptibility and resistivity measurements corroborate such analysis and indicate divalent Eu and Yb, as well as poorly metallic behavior for both Eu11InSb9 and Yb11InSb9. The close relationships between these structures and those of the monoclinic α-Ca21Mn4Sb18 and Ca21Mn4Bi18 are also discussed. 相似文献
13.
The basic mercury(I) chromate(VI), Hg6Cr2O9 (=2Hg2CrO4·Hg2O), has been obtained under hydrothermal conditions (200 °C, 5 days) in the form of orange needles as a by-product from reacting elemental mercury and K2Cr2O7. Hydrothermal treatment of microcrystalline Hg6Cr2O9 in demineralised water at 200 °C for 3 days led to crystal growth of red crystals of the basic mercury(I, II) chromate(VI), Hg6Cr2O10 (=2Hg2CrO4·2HgO). The crystal structures were solved and refined from single crystal X-ray data sets. Hg6Cr2O9: space group P212121, Z=4, a=7.3573(12), b=8.0336(13), , 3492 structure factors, 109 parameters, R[F2>2σ(F2)]=0.0371, wR(F2 all)=0.0517; Hg6Cr2O10: space group Pca21, Z=4, a=11.4745(15), b=9.4359(12), , 3249 structure factors, 114 parameters, R[F2>2σ(F2)]=0.0398, wR(F2 all)=0.0625. Both crystal structures are made up of an intricate mercury-oxygen network, subdivided into single building blocks [O-Hg-Hg-O] for the mercurous compound, and [O-Hg-Hg-O] and [O-Hg-O] for the mixed-valent compound. Hg6Cr2O9 contains three different Hg22+ dumbbells, whereas Hg6Cr2O10 contains two different Hg22+ dumbbells and two Hg2+ cations. The HgI-HgI distances are characteristic and range between 2.5031(15) and 2.5286(9) Å. All Hg22+ groups exhibit an unsymmetrical oxygen environment. The oxygen coordination of the Hg2+ cations is nearly linear with two tightly bonded O atoms at distances around 2.07 Å. For both structures, the chromate(VI) anions reside in the vacancies of the Hg-O network and deviate only slightly from the ideal tetrahedral geometry with average Cr-O distances of ca. 1.66 Å. Upon heating at temperatures above 385 °C, Hg6Cr2O9 decomposes in a four-step mechanism with Cr2O3 as the end-product at temperatures above 620 °C. 相似文献
14.
A novel sodium lead pentaborate, NaPbB5O9, has been successfully synthesized by standard solid-state reaction. The single-crystal X-ray structural analysis showed that NaPbB5O9 crystallizes in the monoclinic space group P21/c with a=6.5324(10) Å, b=13.0234(2) Å, c=8.5838(10) Å, β=104.971(10)°, and Z=4. The crystal structure is composed of double ring [B5O9]3− units, [PbO7] and [NaO7] polyhedra. [B5O9]3− groups connect with each other forming two-dimensional infinite ∞[B5O9]3− layers, while [PbO7] and [NaO7] polyhedra are located between the layers. [PbO7] polyhedra linked together via corner-sharing O atom forming novel infinite ∞[PbO6] chains along the c axis. The thermal behavior, IR spectrum and the optical diffuse reflectance spectrum of NaPbB5O9 were reported. 相似文献
15.
Neeraj Sharma René B. Macquart Mogens Christensen Yu-Sheng Chen 《Journal of solid state chemistry》2009,182(6):1312-4494
The floating-zone furnace method was used to synthesize single crystals of the fluorite-related δ-Bi2O3-type phase Bi38Mo7O78 for the first time. Single crystal synchrotron X-ray diffraction data, in conjunction with ab initio (density functional theory) calculations, were used to solve, optimize, and refine the 5×3×3 commensurate superstructure of fluorite-type δ-Bi2O3 in Pbcn (a=28.7058(11) Å, b=16.8493(7) Å and c=16.9376(6) Å, Z=4, RF=11.26%, wRI=21.67%). The structure contains stepped channels of Mo6+ in tetrahedral environments along the b axis and chains of Mo6+ in octahedral environments along the ac plane. The role of the stepped channels in oxide ion conduction is discussed. The simultaneous presence of both tetrahedral and octahedral coordination environments for Mo6+, something not previously observed in Mo6+-doped δ-Bi2O3-type phases, is supported by charge balance considerations in addition to the results of crystallographic and ab initio analysis. 相似文献
16.
Barium calcium magnesium silicate (BaCa2MgSi2O8), a compound whose space group was obtained via X-ray diffraction data, was re-investigated using neutron diffraction techniques. A combined powder X-ray and neutron Rietveld method revealed that BaCa2MgSi2O8 crystallizes in the trigonal space group P3? (Z=1, a=5.42708(5) Å, c=6.79455(7) Å, V=173.310(4) Å3; Rp/Rwp=5.52%/7.63%), instead of the previously believed space group P3?m1. The difference in the two structures arises from the displacement of the O2 atom. Blue emission from Ba0.98Eu0.02Ca2MgSi2O8 under 325-nm excitation is ascribed to the 4f65d1→4f7 transitions of Eu2+ ions at Ba sites and Ca sites. Site assignment of Eu2+ ions in the titled compound was performed by analysis of emission spectra at temperatures in the range of 4.2-300 K. 相似文献
17.
Ioana Vidican 《Journal of solid state chemistry》2003,170(2):203-210
Single crystals of K3RESi2O7 (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE=Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K3RESi2O7 that contains the rare-earth cation in both a slightly distorted octahedral and an ideal trigonal prismatic coordination environment, while in K3LuSi2O7, containing the smallest of the rare earths, lutetium is found solely in an octahedral coordination environment. The structure of K3LuSi2O7 crystallizes in space group P63/mmc with a=5.71160(10) Å and c=13.8883(6) Å. The structures containing the remaining rare earths crystallize in the space group P63/mcm with the lattice parameters of a=9.9359(2) Å, c=14.4295(4) Å, (K3GdSi2O7); a=9.88730(10) Å, c=14.3856(3) Å, (K3TbSi2O7); a=9.8673(2) Å, c=14.3572(4) Å, (K3DySi2O7); a=9.8408(3) Å, c=14.3206(6) Å, (K3HoSi2O7); a=9.82120(10) Å, c=14.2986(2) Å, (K3ErSi2O7); a=9.80200(10) Å, c=14.2863(4) Å, (K3TmSi2O7); a=9.78190(10) Å, c=14.2401(3) Å, (K3YbSi2O7). The optical properties of the silicates were investigated and K3TbSi2O7 was found to fluoresce in the visible. 相似文献
18.
Artem M Abakumov Marina G Rozova Evgeny V Antipov Gustaaf Van Tendeloo 《Journal of solid state chemistry》2004,177(8):2855-2861
The new Pb5Sb2MnO11 compound was synthesized using a solid-state reaction in an evacuated sealed silica tube at 650°C. The crystal structure was determined ab initio using a combination of X-ray powder diffraction, electron diffraction and high-resolution electron microscopy (a=9.0660(8)Å, b=11.489(1)Å, c=10.9426(9)Å, S.G. Cmcm, RI=0.045, RP=0.059). The Pb5Sb2MnO11 crystal structure represents a new structure type and it can be considered as quasi-one-dimensional, built up of chains running along the c-axis and consisting of alternating Mn+2O7 capped trigonal prisms and Sb2O10 pairs of edge sharing Sb+5O6 octahedra. The chains are joined together by Pb atoms located between the chains. The Pb+2 cations have virtually identical coordination environments with a clear influence of the lone electron pair occupying one vertex of the PbO5E octahedra. Electronic structure calculations and electron localization function distribution analysis were performed to define the nature of the structural peculiarities. Pb5Sb2MnO11 exhibits paramagnetic behavior down to T=5 K with Weiss constant being nearly equal to zero that implies lack of cooperative magnetic interactions. 相似文献
19.
The fluorine-containing derivatives of Sr2MnGaO5.5 were prepared by treatment with XeF2 at temperatures ranging from 300°C to 600°C. The compounds crystallize in a tetragonal unit cell with at≈ap, ct≈2ap (ap—the parameter of the perovskite subcell). An increase in fluorine content is accompanied by a reduction of the Mn oxidation state due to a partial replacement of oxygen by fluorine. The crystal structure of Sr2MnGaO4.78F1.22 was determined by electron diffraction and X-ray powder diffraction (a=3.85559(2) Å, c=7.78289(6) Å, S.G. P4/mmm, RI=0.012, RP=0.019). The structure consists of alternating (MnO2), (SrO) and (GaO0.78F1.22) layers. The Ga atoms are situated in slightly elongated octahedra, the MnO6 octahedra are characterized by two short apical Mn-O distances of 1.876(8) Å and four long equatorial ones of 1.9278(1) Å. This is interpreted as an “apically compressed” type of Jahn-Teller distortion, in contrast to the “apically elongated” one in the Sr2MnGaO5+δ brownmillerites with different oxygen content. Possible structural reasons for the reversed Jahn-Teller effect are discussed. 相似文献
20.
A new compound, Na2Zn5(PO4)4, was identified in the system ZnONa2OP2O5 and high-quality crystal was obtained by the melt method. The crystal structure of this compound was solved by direct method from single crystal X-ray diffraction data. The structure was then refined anisotropically using a full-matrix least square refinement on F2 and the refinement converged to R1=0.0233 and wR2=0.0544. This compound crystallizes in the orthorhombic system with space group Pbcn, lattice parameters a=10.381(2) Å, b=8.507(1) Å, c=16.568(3) Å and Z=4. The structure is made up of 3D [Zn5P4O16]n2n− covalent framework consisting of [Zn4P4O16]n4n− layers. The powder diffraction pattern of Na9Zn21(PO4)17 is explained by simulating a theoretical pattern with NaZnPO4 and Na2Zn5(PO4)4 in the molar ratio of 1:4 and then by Rietveld refinement of experimental pattern. Na2Zn5(PO4)4 melts congruently at 855 °C and its conductivity is 5.63×10−9 S/cm. 相似文献