共查询到20条相似文献,搜索用时 625 毫秒
1.
Use of Nd3+, Eu3+, and Gd3+ as local structural probes allows the determination of the rare earth positions in the NaxSr3?2xLnx(PO4)2 (Ln = La to Tb) and KCaLn(PO4)2 phases (Ln = rare earth). Moreover, a common feature of both series is a particularly high splitting of the excitation and levels of the Gd3+ ions. 相似文献
2.
A series of new compounds Ln(GaM2+)O4 and Ln(AlMn2+)O4 having a layer structure were successfully prepared [Ln = Lu, Yb, Tm, Er, Ho, and Y, and M = Mg, Mn, Co, Cu, and Zn]. The synthesis conditions and the unit cell parameters for 23 compounds have been determined. These compounds are isostructural with YbFe2O4 (space group Å, and c = 25.109(2) Å). 相似文献
3.
Electrical conductivity measurements of Th3P4-type EuLn2S4 (Ln = LaGd) compounds have been made as functions of temperature and sulfur vapor pressure. These compounds are all p-type semiconductors, and their conductivities at room temperature have almost the same values for the specimens from EuLa2S4 to EuNd2S4 but increase on going from EnNd2S4 to EuGd2S4. In addition, the conductivity of EuGd2S4 is sensitive to sulfur vapor pressure and obeys the relationship . The mechanism of electrical transport in these compounds is discussed. 相似文献
4.
K3Sb3P2O14 crystallizes in the rhombohedral system, space group with a = 7.147(1) Å, c = 30.936(6) Å, Z = 3. The structure was determined from 701 reflections collected on a Nonius CAD4 automatic diffractometer with radiation. The final R index and the weighted Rw index are 0.033 and 0.042, respectively. The structure is built up from layers of SbO6 octahedra and PO4 tetrahedra sharing corners. The potassium ions are situated between the (Sb3P2O14)3? covalent layers. 相似文献
5.
Rare earth tungstates of the stoichiometry Ln2WO6 where Ln = Ce to Lu have been prepared and their lattice parameters were refined by a least-squares method. They have two structures: the symmetry for the compositions Ce2WO6 through Ho2WO6, and a monoclinic group from Er2WO6 to Lu2WO6 crystallizing most likely in the or structure. High pressure modifications are described for Dy2WO6 and Ho2WO6. 相似文献
6.
J.D. Garrett J.E. Greedan R. Faggiani S. Carbotte I.D. Brown 《Journal of solid state chemistry》1982,42(2):183-190
Single crystals of the fast-ion conductor Ag16I12P2O7 were prepared and their structure ( Å) was determined by X-ray diffraction (r = 0.08). The I atoms form a close-packed array leaving channels occupied by P2O4?7 ions running along the c axis. The Ag atoms are disordered over four different types of site with occupation numbers ranging from 0.12 to 0.52. Each Ag+ ion coordination polyhedron shares several faces with adjacent polyhedra providing ready paths for Ag+ ion conduction. 相似文献
7.
The phases SrLnMnO4 (Ln = La, Nd, Sm, Gd), BaLnMnO4 (Ln = La, Nd) and the solid solutions M1+xLa1?xMnO4 (M = Sr: 0 ? x ? 1; M = Ba: 0 ? x ? 0.50) have a K2NiF4-type structure. The ratio of the unit cell is related to the electronic configuration of the Mn3+ ions. 相似文献
8.
A preliminary study of the PbF2LnF3 systems (Ln = lanthanides and Y) has allowed the characterisation of three phases: a disordered fluorite-like solid solution Pb1?xLnxF2+x the domain of which increases with increasing temperature and dopant ion radius, and two anion-excess fluorite related superstructures: Pb2YF7 (tetragonal, space group I4 or ) and Pb4Ln3F17 with Ln = SmLu (rhombohedral, space group ). The crystallographic characteristics of the two ordered phases have been confirmed by electron diffraction. 相似文献
9.
G. Eulenberger 《Journal of solid state chemistry》1984,55(3):306-313
The new compound Tl6[Ge2Te6] was prepared by thermal synthesis from the elements. The material is triclinic, space group , with a = 9.471(2), b = 9.714(2), c = 10.389(2) Å, α = 89.39(1), β = 97.27(1), γ = 100.79(1)°, and Z = 2. The crystal structure was determined from single-crystal intensity data measured by means of an automated four-circle diffractometer and refined to an R value of 0.053 for 1831 observed reflections. Tl6[Ge2Te6] is characterized by Ge2Te6 units with GeGe bonds which are linked into a three-dimensional structure by Tl atoms coordinated to essentially six Te atoms. The most important mean distances are Å, Å, and Å. The lone 6s electron pairs of the thallium(I) atoms exhibit significant stereochemical activity. Tl6[Ge2Te6] represents a new structure type. 相似文献
10.
Fe2P2O7 crystallizes in the space group with lattice parameters a = 6.649(2)Å, b = 8.484(2)Å, c = 4.488(1)Å, α = 90.04°, β = 103.89(3)°, γ = 92.82(3)°, and ?cal = 3.86 g/cc. It is essentially isostructural with β-Zn2P2O7. As in the Zn compound, the bridging oxygen atom in the P2O7 group shows a high anisotropic thermal motion. It appears that the P-O-P bond angle is linear as a result of extensive π bonding with the p orbitals on the bridging oxygen atom. The high thermal motion is vibration of the atom into cavities in the structure. 相似文献
11.
The crystal structures of the apatites Ba10(PO4)6F2(I), Ba6La2Na2(PO4)6F2(II) and Ba4Nd3Na3(PO4)6F2 (III) have been determined by single-crystal X-ray diffraction. All three compounds crystallize in a hexagonal apatite-like structure. The unit cells and space groups are: I, a = 10.153(2), c = 7.733(1)Å, Å, ; III, a = 9.786(2), c = 7.281(1)Å, . The structures were refined by normal full-matrix crystallographic least squares techniques. The final values of the refinement indicators Rw and R are: I, Rw = 0.026, R = 0.027, 613 observed reflections; II, Rw = 0.081, R = 0.074, 579 observed reflections; III, Rw = 0.062, R = 0.044, 1262 observed reflections.In I, the Ba(1) atoms located in columns on threefold axes, are coordinated to nine oxygen atoms; the Ba(2) sites form triangles about the F site and are coordinated to six oxygen atoms and one fluoride ion. The fluoride ions are statistically displaced ~0.25 Å from the Ba(2) triangles. This displacement of the F ions is analogous to the displacement of OH ion in Ca10(PO4)6(OH)2.The structures of II and III contain disordered cations. In II there is disorder between La and Na in the column cation sites as well as triangle sites. In III, Nd and Na ions are ordered in the column sites, but there is disorder among Ba and the remaining Nd and Na ions in the triangle sites to give an average site population of . The coordination of the rare earth ions and Na ions in the ordered column sites are nine and six oxygens, respectively, in accord with the greater charge of the rare earth ions as compared with Na. The F ions in both II and III suffer from considerable disorder in position, and their locations are not precisely known. 相似文献
12.
The structure of a crystal was established by X-ray analysis. The solution in the cell of symmetry , with a = 6.6702(5), b = 5.3228(8), c = 8.9091(8) Å, β = 100.546(7)°, Z = 1, has led to R = 0.033 and Rw = 0.036 for 2155 reflections with . This structure can be described as two octahedra-wide ReO3-type slabs connected through “planes” of PO4 tetrahedra. A new structural family KxP2W2nO6n+4 can be foreseen which is closely related to the orthorhombic P4W8O32 and the monoclinic RbxP8W8nO24n+16 series. 相似文献
13.
Two original compounds, Ln4?2xBa2+2xZn2?xO10?2x, were isolated for Ln = La, Nd and 0 ≤ x ≤ 0.25. These oxides are tetragonal with a and c parameters close to 6.91 and 11.59 Å, respectively, for lanthanum, and 6.75 and 11.54 Å for neodymium. The structure of these phases was determined from X-ray powder patterns in the most symmetric space group, , using Patterson and Fourier functions for x = 0. The structure should be compared to that of copper oxides La4?2xBa2+2xCu2?xO10?2x: it is built up of identical Ln2O5 layers formed from face- and edge-sharing LnO8 polyhedra, between which Ba2+ and Zn2+ ions are inserted. Contrary to the copper compounds, two successive Ln2O5 layers are rotated by 90°, involving a doubling of c. The result for Zn2+ is tetrahedral coordination, while the coordination of Ba2+ becomes a bicapped antiprism. 相似文献
14.
The reactions (I) Hg2Cl2(s) + Br2(g) and (II) HgCl2(s) + HgBr2(s) have been investigated by an X-ray method. Both the reactions yield two forms of the mixed halide HgClBr, designated as α-HgClBr and β-HgClBr. The cell parameters of the two are as follows:α-HgClBr: , , , z = 4, ? = 5.91 g/cm3. The powder pattern and cell parameters are similar to that of HgCl2. Therefore it is probable that the chlorine atoms, in the linear halogenHghalogen molecules of HgCl2 structure have been replaced by bromines, and since the radius of the bromine atom is larger than that of chlorine, the lattice is larger in this case.β-HgClBr: , , , z = 4, ? = 5.40. These parameters are the same as those reported in the literature for β-Hg(ClBr)2, and its X-ray powder pattern is similar to HgCl2. Therefore this phase also has linear halogenHghalogen molecules but the distribution of Cl and Br atoms is perhaps random.Heating the products (I) and (II) up to the melting point increases the amount of α phase and decreases the β phase, whereas crystallization increases the β phase. DTA study has supported the X-ray findings. 相似文献
15.
α-LnNb3O9 (Ln = La, Pr, Nd) compounds have been prepared hydrothermally from acidic solutions. In comparison to the previously reported orthorhombic β modifications, α-LnNb3O9 compounds are monoclinic. The structure of α-PrNb3O9 was determined with a = 5.3784(6), b = 7.602(2), c = 16.344(2) Å, and β = 92.21(1)°, space group . It is built of double and single chains of corner-shared NbO6 octahedra extended along the b axis. Praseodymium atoms reside in tunnels along the b axis and are in eight-coordination with oxygen. All α-LnNb3O9 compounds can be irreversibly converted to the β modification by heating in air to 1200°C. The X-ray excited luminescence of Sm-, Eu-, Tb-, and Dy-doped α-LaNb3O9 is also reported. 相似文献
16.
Barium-zinc decametaphosphate, Ba2Zn3P10O30, is monoclinic, , with the unit cell parameters a = 21.738(15), b = 5.356(5), c = 10.748(8) Å, β = 99.65(3)° and Z = 2. The crystal structure was solved with a final R value of 0.041. This salt provides the first structural evidence for the existence of a 10-phosphorus ring anion. 相似文献
17.
Peter Rogl 《Journal of solid state chemistry》1984,55(3):262-269
The crystal structure of Sc2Ru5B4 has been determined by single-crystal X-ray analysis. Sc2Ru5B4 crystallizes in the primitive monoclinic space group with a = 9.983(6), b = 8.486(4), c = 3.0001(3)Å, γ = 90.01(7)°, Z = 2. Deviations from the orthorhombic space group Pbam-D92h are small but significant. Intensity measurements were obtained from a four-circle diffractometer. The structure was solved by Patterson methods and refined by full matrix least-squares calculation. for an asymmetric set of 863 independent reflections (|F0|>2σ(F0)). The crystal structure is characterized by two different types of boron atoms: (a) isolated borons B(1) and B(3) in distorted trigonal Ru-prisms with tetrakaidekahedral metal coordination: 6Ru + 3Sc, and (b) boron atoms B(2) and B(4) with a pronounced tendency to form boron pairs (B(2)-B(2) = 1.86 Å, B(4)-B(4) = 1.89 Å); the metal coordination of these boron atoms is 6Ru + 2Sc. Sc atoms have a coordination number of 17 consisting of 10Ru + 2Sc + 5B. The crystal structure of Sc2Ru5B4 is a pentagon layer structure (Ru, B atoms) with a 4.3.4.32-secondary layer of Sc atoms. The structure is furthermore related to the structure types of Ti3Co5B2 and CeCo3B2. From powder photographs Sc2Os5B4 is isotypic. No superconductivity was observed for Sc2(Ru, Os)5B4 down to 1.5 K. 相似文献
18.
Bernadette Saubat Marcus Vlasse Claude Fouassier 《Journal of solid state chemistry》1980,34(3):271-277
To obtain rare earth luminescent materials with weak concentration quenching, the B2O3-rich portion of the ternary diagram Ln2O3MgOB2O3 (Ln = rare earth) has been investigated. A ternary phase of composition LnMgB5O10 has been found for Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er. These compounds all crystallize in the monoclinic space group . The structure has been determined on a LaMgB5O10 crystal. A full-matrix least-squares refinement leads to R = 0.039. The structure can be described as being made of (B5O105?)n two-dimensional layers linked together by the lanthanum and magnesium ions. The rare earth atom coordination polyhedra form isolated chains. These borates are isostructural with some rare earth cobalt borates. 相似文献
19.
Reaction of the 16 electron monomer [Co(η5-C5H5)(S2C2{CN}2)] with various tertiary phosphines and phosphites (L) gives readily the 18 electron monomers [Co(η5-C5H5)(S2C2{CN}2)L] which for L = P(OR)3 have J(C55) ca. 6 Hz but J(C55) = 0 for L = PR3. 相似文献
20.
The crystal structure of SnC2O4 has been determined by X-ray single-crystal techniques and refined to R = 0,018 for 1139 reflections. The cell is monoclinic, space group with Z = 4 formula units, the parameters being a = 10,375(3)Å. b = 5,504(2)Å, c = 8,234(3)Å, β = 125,11(2)°. The oxalato groups, located on symmetry centers, are chelated to two Sn atoms through one oxygen on each carbon atom, giving rise to an infinite string (SnC2O4)n. The Sn(II) atom is one-side bonded to four oxygen atoms with two SnO bonds of 2,232(2) Å and two of 2,393(2) Å. The tin atom is in a distorted trigonal bipyramid SnO4E, the lone pair E occupying one of the apices of the equatorial trigonal base of the polyhedron. Crystal structure comparison with disodium bisoxalatostannate(II), Na2Sn(C2O4)2, permits one to deduce SnC2O4 by crystallographic shear operation of periodicity. Na2Sn(C2O4)2 can be described as an intergrowth of SnC2O4 and Na2C2O4 structures and consldered as the first member of a new series Na2Sn1+n(C2O4)2+n with n integer ? 0. 相似文献