首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
A new phosphoniobate, RbNb2PO8, with an intersecting tunnel structure, has been synthesized. It crystallizes in the Pnma space group with a = 13.815(1) Å, b = 15.884(2) Å, c = 12.675(2) Å, and Z = 16. The full matrix least-squares refinement led to R = 0.041 and Rw = 0.050. The host lattice is derived directly from that of the hexagonal tungsten bronzes (HTB) by an ordered substitution of PO4 tetrahedra, forming two sorts of tunnels running along b and a, respectively, where the Rb+ ions are located. The first type of tunnel results from the stacking of six-sided HTB-type rings (5NbO6 octahedra + 1PO4 tetrahedron) with seven-sided rings (4NbO6 octahedra + 3PO4 tetrahedra), whereas the second type of tunnel consists of brownmillerite rings (4NbO6 octahedra + 2 PO4 tetrahedra).  相似文献   

2.
Lithium iron(III) monophosphate-monohydrogen-monophosphate, Li2Fe[(PO4)(HPO4)], was synthesized under mild hydrothermal conditions and its crystal structure was determined by single crystal X-ray diffraction methods. Crystallographic data: monoclinic, P121/n1 (no. 14), a = 4.8142(2) Å, b = 7.9898(4) Å, c = 7.4868(4) Å, β = 104.398(3)°, V = 278.93(2) Å3, Z = 2, Dx = 3.104 g · cm-3. The structure is characterized by FeO6 octahedra sharing common O-corners with six neighbouring PO4 tetrahedra to form a three-dimensional framework. Lithium cations are located within channels running along [100]. The channels are formed by eight-membered rings resulting from the connection of alternating FeO6 octahedra (4×) and phosphate tetrahedra (4×). High-resolution diffraction data allowed to refine a split model for the position of the hydrogen atom. Magnetization data confirm the valence state 3+ for iron and detect an antiferromagnetic ordering of the iron moments below 23.6 K. Thermal decomposition of the compound was investigated by DTA/TG methods.  相似文献   

3.
This paper reports the hydrothermal synthesis and crystal structure refinement of diiron(II) phosphate hydroxide, FeII2(PO4)(OH), obtained at 1063 K and 2.5 GPa. This phosphate is the synthetic analogue of the mineral wolfeite, and has a crystal structure topologically identical to those of minerals of the triplite–triploidite group. The complex framework contains edge‐ and corner‐sharing FeO4(OH) and FeO4(OH)2 polyhedra, linked via corner‐sharing to the PO4 tetrahedra (average P—O distances are between 1.537 and 1.544 Å). Four five‐coordinated Fe sites are at the centers of distorted trigonal bipyramids (average Fe—O distances are between 2.070 and 2.105 Å), whereas the coordination environments of the remaining Fe sites are distorted octahedra (average Fe—O distances are between 2.146 and 2.180 Å). The Fe—O distances are similar to those observed in natural Mg‐rich wolfeite, except for two Fe—O bond distances, which are significantly longer in synthetic Fe2+2(PO4)(OH).  相似文献   

4.
A new phosphate, sodium calcium magnesium tetrakis(phosphate), Na8Ca1.5Mg12.5(PO4)12, has been synthesized by a flux method. Its novel structure consists of MgOx (x = 5 and 6) polyhedra and MO7 (M = Mg or Na) octahedra linked directly through common corners or edges to form a rigid three‐dimensional skeleton, reinforced by corner‐sharing between identical Mg12MO48 units. The connection of these units by the PO4 tetrahedra induces cavities and crossing tunnels where the Na+ and Ca2+ cations are located. This structural model was supported by a 31P NMR spectroscopy study which confirmed the existence of 12 crystallographically independent sites for the P atoms.  相似文献   

5.
Dicaesium divanadium trioxide phosphate hydrogenphosphate, Cs2V2O3(PO4)(HPO4), (I), and dicaesium tris[oxidovanadate(IV)] hydrogenphosphate dihydrate, Cs2[(VO)3(HPO4)4(H2O)]·H2O, (II), crystallize in the monoclinic system with all atoms in general positions. The structures of the two compounds are built up from VO6 octahedra and PO4 tetrahedra. In (I), infinite chains of corner‐sharing VO6 octahedra are connected to V2O10 dimers by phosphate and hydrogenphosphate groups, while in (II) three vanadium octahedra share vertices leading to V3O15(H2O) trimers separated by hydrogenphosphate groups. Both structures show three‐dimensional frameworks with tunnels in which Cs+ cations are located.  相似文献   

6.
A series of alluaudite Na2Fe3?xMnx(PO4)3 microcompounds, which self‐assembled from primary nanorods, were prepared successfully through a solvothermal method. As a promising candidate cathode for sodium‐ion batteries, it is necessary to obtain a deeper understanding of the relationship between the structure and physicochemical properties of these materials. The local electronic and geometric environments were systematically investigated, for the first time, by using a combination of soft/hard X‐ray absorption, IR, and Mössbauer spectroscopy. The results show that the electrochemical performance is not only associated with morphology, but also with the electronic and crystalline structure. With the introduction of manganese into the lattice, the long‐range order maintains the isostructural framework and the lattice parameters expand as expected. However, for short‐range order, PO4 tetrahedra and MO6 octahedra (M=Fe and Mn) become more severely distorted as a function of Mn concentration. Meanwhile, larger MnO6 octahedra will compress the space of FeO6 octahedra, which will result in stronger core/electron–electron interactions for Fe, as characterized by hard/soft X‐ray absorption spectra. These slight changes in the electronic and local structures lead to different electrochemical performances with changes to the manganese content. Moreover, other physicochemical properties, such as magnetic behavior, are also confirmed to be correlated with these different electron interactions and local geometric environments.  相似文献   

7.
A room-temperature structural model of titanium pyrophos­phate, TiP2O7, has been determined from synchrotron X-ray data. The structure consists of TiO6 octahedra and PO4 tetrahedra sharing corners in a three-dimensional network. The PO4 tetrahedra form P2O7 groups connecting the TiO6 octahedra. The 3 × 3 × 3 superstructure differs substantially from the parent AB2O7 structure. The P—O—P bonding angles of the pyrophosphate group are between 141.21 (12) and 144.51 (13)° for those groups not located on the threefold axis. The individual TiO6 octahedra and PO4 tetrahedra are somewhat distorted.  相似文献   

8.
The structure of the title compound, potassium trinickel arsenate diarsenate, is built up from corner‐ and edge‐sharing NiO6 octahedra, AsO4 tetrahedra and As2O7 groups, giving rise to a polyhedral connectivity which produces large tunnels running along the crystallographic [010] direction. The K+ cations are located within these tunnels.  相似文献   

9.
The title synthesized hypophosphite has the formula V(H2PO2)3. Its structure is based on VO6 octahedra and (H2PO2) pseudo‐tetrahedra. The asymmetric unit contains two crystallographically distinct V atoms and six independent (H2PO2) groups. The connection of the polyhedra generates [VPO6H2]6− chains extended along a, b and c, leading to the first three‐dimensional network of an anhydrous transition metal hypophosphite.  相似文献   

10.
The First Vanadium(III) Borophosphate: Synthesis and Crystal Structure of CsV3(H2O)2[B2P4O16(OH)4] CsV3(H2O)2[B2P4O16(OH)4] was prepared under mild hydrothermal conditions (T = 165 °C) from mixtures of CsOH(aq), VCl3, H3BO3, and H3PO4 (molar ratio 1 : 1 : 1 : 2). The crystal structure was determined by X‐ray single crystal methods (monoclinic; space group C2/m, No. 12): a = 958.82(15) pm, b = 1840.8(4) pm, c = 503.49(3) pm; β = 110.675(4)°; Z = 2. The anionic partial structure contains oligomeric units [BP2O8(OH)2]5–, which are built up by a central BO2(OH)2 tetrahedron and two PO4 tetrahedra sharing common corners. VIII is octahedrally coordinated by oxygen of adjacent phosphate tetrahedra and OH groups of borate tetrahedra as well as oxygen of phosphate tetrahedra and H2O molecules, respectively (coordination octahedra VO4(OH)2 and VO4(H2O)2). The oxidation state +3 for vanadium was confirmed by measurements of the magnetic susceptibility. The trimeric borophosphate groups are connected via vanadium centres to form layers with octahedra‐tetrahedra ring systems, which are likewise linked via VIII‐coordination octahedra. Overall, a three‐dimensional framework constructed from VO4(OH)2 and VO4(H2O)2 octahedra as well as BO2(OH)2 and PO4 tetrahedra results. The structure contains channels running along [001], which are occupied by Cs+ in a distorted octahedral coordination (CsO4(H2O)2).  相似文献   

11.
A new iron(II) orthophosphate K[Fe(PO4)] has been obtained by hydrothermal synthesis and its crystal structure was determined by single‐crystal X‐ray diffraction: space group P21/n, Z = 8, a = 9.6199(10), b = 8.6756(8), c = 10.8996(13) Å, β = 115.577(8)° at 193 K, R = 0.023. FeII shows coordination numbers (CN) 4 (distorted tetrahedral) and CN 5 (distorted trigonal bipyramidal). The [FeO4] and [FeO5] units form together with the [PO4] tetrahedra a microporous 3D para‐framework with open channels along the a and b directions. The potassium ions positioned in the channels show CN 7 and 8. The structural relations within the morphotropic row of non‐isotypic K[M(PO4)] structures (M = Zn, Ni, Mn, Fe) are discussed on the basis of common basic structural units.  相似文献   

12.
The crystal structure of tripotassium pentairon hexaphosphate has been determined by single‐crystal X‐ray diffraction. The structure contains one Fe atom on a center of symmetry, one K, two Fe and two P atoms on twofold axes, and one Fe, two P and one K atom in general positions. The K3Fe5(PO4)6 structure consists of a complex three‐dimensional framework of corner‐sharing between iron polyhedra, and corner‐ and edge‐sharing between PO4 tetrahedra and iron polyhedra (FeO5 and FeO6). This linkage between iron and phosphorus forms intersecting channels containing the K atoms.  相似文献   

13.
This study presents the first structural report of natural isokite (calcium magnesium phosphate fluoride), with the formula CaMg(PO4)F0.8(OH)0.2 (i.e. some substitution of OH for F), based on single‐crystal X‐ray diffraction data. Isokite belongs to the C2/c titanite mineral group, in which Mg is on an inversion centre and the Ca, P and F/OH atoms are on twofold axes. The structure is composed of kinked chains of corner‐sharing MgO4F2 octahedra that are crosslinked by isolated PO4 tetrahedra, forming a three‐dimensional polyhedral network. The Ca2+ cations occupy the interstitial sites coordinated by six O atoms and one F anion.  相似文献   

14.
The crystal structure of cobalt vanadophosphate dihydrate {systematic name: poly[diaqua‐μ‐oxido‐μ‐phosphato‐hemicobalt(II)vanadium(II)]}, Co0.50VOPO4·2H2O, shows a three‐dimensional framework assembled from VO5 square pyramids, PO4 tetrahedra and Co[O2(H2O)4] octahedra. The CoII ions have local 4/m symmetry, with the equatorial water molecules in the mirror plane, while the V and apical O atom of the vanadyl group are located on the fourfold rotation axis and the P atoms reside on sites. The PO4 tetrahedra connect the VO5 polyhedra to form a planar P–V–O layer. The [Co(H2O)4]2+ cations link adjacent P–V–O layers via vanadyl O atoms to generate an unprecedented three‐dimensional open framework. Powder diffraction measurements reveal that the framework collapses on removal of the water molecules.  相似文献   

15.
Spheniscidite, a synthetic iron phosphate mineral has been synthesized by hydrothermal methods. The material is isotypic with another iron phosphate mineral, leucophosphite. Spheniscidite crystallizes in the monoclinic spacegroupP21/n. (a=9·845(1),b=9·771(3),c=9·897(1),β=102·9°,V=928·5(1),Z=4,M=372·2,d calc=2·02 g cm−3 andR=0·02). The structure consists of a network of FeO6 octahedra vertex-linked with PO4 tetrahedra forming 8-membered one-dimensional channels in which the NH4 + ions and H2O molecules are located. The material exhibits reversible dehydration and good adsorption behaviour. Magnetic susceptibility measurements indicate that the solid orders antiferromagnetically.  相似文献   

16.
A new stibium phosphate, lithium barium bis(antimony oxide) tris(phosphate), LiBa(SbO)2(PO4)3, was prepared by the molten salt method with LiF as the flux. The crystal structure consists of an original three‐dimensional anionic framework of [(SbO)2(PO4)3] built from PO4 tetrahedra sharing their corners with SbO6 octahedra. This framework delimits one‐dimensional tunnels where the lithium(I) and barium(II) ions are located. The UV–Vis spectrum shows that LiBa(SbO)2(PO4)3 was transparent from 350 to 800 nm, and is thus suitable as a luminescent host matrix. We then used Tb3+ and Eu3+ activators to test its luminous performance and the purities of the prepared phosphors were studied by powder X‐ray diffraction analysis with Rietveld refinements. Photoluminescence (PL) studies reveal that the emission spectra of 1 mol% RE3+‐doped (RE = Tb and Eu) samples can be excited by 371 and 394 nm light, emitting green and orange–red light, respectively, for Tb3+ and Eu3+. The CIE coordinates were measured to be (0.295, 0.571) and (0.6027, 0.3967), and the luminescent lifetimes were calculated as 0.178 and 1.159 ms, respectively.  相似文献   

17.
IntroductionInthelastfewyearsthesearchfornewmaterialswithmicroporousandzeolite analogoussystemshasprimarilyfocusedonaluminumphosphatesandaluminosilicatecom poundssubstitutedwithavarietyofatoms .1 3 Cobalt sub stitutedaluminophosphatesaresystematicallystudiedmainlyduetotheirpotentialuseassolid acidcatalysts .Insuchmaterials ,theBr nstedacidsiteisgeneratedbyeachsubstitutionofAl(III)byCo(II)inwhichaprotonisneededtobalancethecharge .4 7Tofindnewtypeofze oliticmaterials ,theborophosphatemateri…  相似文献   

18.
Three compounds ASb2(SO4)2(PO4) (A = H3O+, K, Rb) were obtained from the reactions of Sb2O3, A2CO3 (A = Li, Rb) or K2SO4 and NH4H2PO4 in H2SO4 (98 %) at 220–250 °C. Their structures were determined by single‐crystal X‐ray diffraction. All compounds crystallize in the triclinic space group P$\bar{1}$ (no.2) and are isostructural. The crystal structures consist of two‐dimensional 2[Sb2(SO4)2(PO4)] anionic layers and alkali cations, which are located between anionic layers. The anionic layers are composed of [SbO4] ψ‐trigonal bipyramids, [SbO5] ψ octahedra, [SO4] tetrahedra, and [PO4] tetrahedra. All compounds are characterized by solid state UV/Vis/NIR diffuse reflectance spectra, FT‐IR spectroscopy, and Raman spectroscopy.  相似文献   

19.
Two new mixed‐valence iron phosphates, namely heptairon pentaphosphate hydrogen phosphate, Fe6.67(PO4)5.35(HPO4)0.65, and heptairon tetraphosphate bis(hydrogen phosphate), Fe6.23(PO4)4.45(HPO4)1.55, have been synthesized hydrothermally at 973 K and 0.1 GPa. The structures are similar to that of FeII3FeIII4(PO4)6 and are characterized by infinite chains of Fe polyhedra parallel to the [101] direction. These chains are formed by the Fe1O6 and Fe2O6 octahedra, alternating with the Fe4O5 distorted pentagonal bipyramids, according to the stacking sequence ...Fe1–Fe1–Fe4–Fe2–Fe2.... The Fe3O6 octahedra and PO4 tetrahedra connect the chains together. FeII is localized on the Fe3 and Fe4 sites, whereas FeIII is found in the Fe1 and Fe2 sites, according to bond‐valence calculations. Refined site occupancies indicate the presence of vacancies on the Fe4 site, explained by the substitution mechanism FeII + 2(PO43−) = vacancies + 2(HPO42−).  相似文献   

20.
Trilithium aluminium trimolybdate(VI), Li3Al(MoO4)3, has been grown as single crystals from α‐Al2O3 and MoO3 in an Li2MoO4 flux at 998 K. This compound is an example of the well known lyonsite structure type, the general formula of which can be written as A16B12O48. Because this structure can accomodate cationic mixing as well as cationic vacancies, a wide range of chemical compositions can adopt this structure type. This has led to instances in the literature where membership in the lyonsite family has been overlooked when assigning the structure type to novel compounds. In the title compound, there are two octahedral sites with substitutional disorder between Li+ and Al3+, as well as a trigonal prismatic site fully occupied by Li+. The (Li,Al)O6 octahedra and LiO6 trigonal prisms are linked to form hexagonal tunnels along the [100] axis. These polyhedra are connected by isolated MoO4 tetrahedra. Infinite chains of face‐sharing (Li,Al)O6 octahedra extend through the centers of the tunnels. A mixed Li/Al site, an Li, an Mo, and two O atoms are located on mirror planes.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号