共查询到20条相似文献,搜索用时 15 毫秒
1.
Nguyen-Huy Dung Pardo Marie-Paule Dogguy.Smiri Leïla 《Materials Research Bulletin》1982,17(3):293-300
The Mn0.23Ga1.85S3 phase belongs to the solid solution , stable at low temperature in the Ga2S3MnS system. It is hexagonal superstructure of the wurtzite, with the Ga2S3α′ type (; Z = 6; space groupe P61 or P65). Its crystal structure has been refined by the least squares method to a final R = 0.06 with 323 independant reflections. This structure is closely related to Ga2S3 α described by Hahn and Frank, and differs only by the partial occupation of the vacant metal site of Ga2S3 by Mn atoms in statistical disorder. 相似文献
2.
Epitaxial films of the low temperature modification of Cu2Se deposited onto NaCl single-crystal substrates at 200°C and 400°C have been investigated. The diffraction pattern of this phase was indexed on the basis of a hexagonal lattice with unit cell parameters a = 7.07 and . These parameters are related to the parameters of the f.c.c. phase by the relations and . 相似文献
3.
Europium orthoborate and strontium orthoborate crystallize in the rhombohedral system with two formula units in a cell of dimensions , αR=85.17° for Eu3B2O6, and , αR=85.00° for Sr3B2O6. The equivalent hexagonal lattice parameters are , , and , respectively. Eu3B2O6 appears to be ferromagnetic below 7.5K. 相似文献
4.
par Leïla Dogguy-Smiri Nguyen-Huy Dung Marie-Paule Pardo 《Materials Research Bulletin》1978,13(7):661-666
Twins of were used for crystal structure determination. Twinning is explained by a reticular pseudomerihedry. Axis, plane and obliquity of the twin have been determined. Cell dimensions are: ; ; α = β = γ = 90°; space group 14; Z = 2. The final R value is 0.059. The material is isostructural with CdGa2S4. 相似文献
5.
Tridimensional P2NbS8 crystallizes in P4?n2 tetragonal space group, with , , and Z = 4. The structure was anisotropically refined down to R = 2.3% from 468 reflexions and 53 variables. It is built from [Nb2S12] biprismatic bicapped units (average ) made of S?II and S?II2 anions (dianionic distance of 2.014(3) Å). The niobium atoms are found as isolated NbIV ? NbIV pairs () in these niobium group otherwise linked to each other through (PS4) tetrahedral units (average ) themselves constituting interbonded [P4S12] rings. The P2NbS8 three-dimensional network thus obtained is compared to the (2D) P2NbS8, layered phase already described. 相似文献
6.
Preparation chimioue et structure cristalline des tellurites de sodium et d'argent: Na2TeO3, Ag2TeO3
Sodium and silver tellurites are isotypic. The space group is . For Ag2TeO3, the parameters of the monoclinic unit cell are: a = 7.000(2), b = 10.509(5), , β = 91°51(5). The structures of sodium and silver tellurites has been determined. For Ag2TeO3, a R value of 0.047 is reached with 829 reflexions and for Na2TeO3 R = 0.024 with 1125 reflexions. The framework is built with MeO6 edge sharing octahedra, Me = Ag,Te. Ag2TeO3 is a distortion of NaCl Structure. 相似文献
7.
The existence has been proved, for the first time, in the LaLiFeO system of the phase (La1.75Li.25) (Fe.5Li.5)O4?x with tetragonal symmetry (; ; ) and K2NiF4-type structure.This phase gives probably the first example of lithium distribution in both A and B sites of A2BO4-type mixed oxides. The high ratio suggests a strong elongation of FeO6 octahedra induced by a high spin Fe(IV) d4 configuration. The results of structural studies and of Mössbauer analysis, confirming the above conclusions, are reported. 相似文献
8.
PbU2Se5 crystallizes in a monoclinic unit cell ; ; ; β = 90° of space group , Z = 4. The crystal structure has been determined for 1251 independant reflections and refined to a final R value of 0,068. Two kinds of uranium sites are found; the average U-Se distances are 2,97 Å for eight-coordination and 2,88 Å in seven-coordination. The average Pb-Se distance for eight-coordination is 3,20 Å. This structure explains the solid solution between PbU2Se5 and U3Se5. 相似文献
9.
P.D. Battle 《Materials Research Bulletin》1981,16(4):397-405
Neutron diffraction experiments have been performed to determine the structures of Ba2LaRuO6 and Ca2LaRuO6. Both are ordered, distorted perovskites. Ba2LaRuO6 is monoclinic, space group with , , , β=90.44(1)o. The A sites are occupied by barium and the B sites by an ordered arrangement of lanthanum and ruthenium. Ca2LaRuO6 is triclinic, space group P1 with a0=5.6179(5), b0=5.8350(5), c0=8.0667(4), α=90.0o, β=89.76(1)o, γ=90.0o. The A sites are occupied by calcium and lanthanum in a disordered manner, and the B sites are occupied by an ordered arrangement of calcium and ruthenium. The results reported in this paper thus contradict those of previous workers. The low-temperature magnetic structures are discussed briefly. 相似文献
10.
Three new compounds, X3InO6 (X = Gd, Tb, Lu) were prepared at 1–4 GPa, ~1050°C. They are monoclinic, space group with , , , β ~ 95° and Z = 4. 相似文献
11.
Jean-Pierre Bastide Patrick Germain Jack Thourey Guy Pérachon 《Materials Research Bulletin》1984,19(1):7-10
Sodium pentafluorotellurate (IV) NaTeF5 has been prepared by slow evaporation of a mixture of sodium fluoride and tellurium dioxyde in 50 % aqueous hydrofluoric acid.NaTeF5 has an orthorhombic structure, parameters of which are 相似文献
12.
M.T. Averbuch-Pouchot 《Materials Research Bulletin》1981,16(4):407-411
NH4HSO4·NH4H2PO4 is monoclinic with Z = 2 and the following unit cell dimensions : a = 7.723(5), b = 7.540(5), , β = 101.32(5)°. Crystal structure of this salt has been solved with a final R value 0.028. As in the corresponding potassium salt PO4 and SO4 tetrahedra are randomly distributed.A complete hydrogen bonding pattern is given. 相似文献
13.
J.J. Verkelis 《Materials Research Bulletin》1974,9(8):1063-1065
Single crystals of semiconducting compound In2Te5 were grown by chemical transport employing iodine as a transport agent. The crystals had a plate-like habit with the [100] direction perpendicular to the flat surface of the platelets. Nominal dimensions are 10 × 1 × 0.05 mm. In2Te5 has a monoclinic structure with dimensions of the base centered cell: , , , β = 92°5′. The space group is . Pycnometric density is 5.96 g/cm3. The single crystals were all p-type. The conductivity, thermoelectric power and hardness were about 10?5Ω?1cm?1, 650 mkV/°C, and 30 kg/mm2, respectively. The minimum energy gap is 1.26 eV. 相似文献
14.
(CH3NH3)2CdBr4 and Cs2CdBr4 are two compounds with a tetrahedral CdBr4-coordination. Their room temperature structures are determined. (CH3NH3)2CdBr4: monoclinic, , , , , β = 96.194(11) °, z = 4. Cs2CdBr4: orthorhombic, Pnma, , , , z = 4. 相似文献
15.
M. Cambini 《Materials Research Bulletin》1974,9(11):1469-1480
The ordered structure of the V8N subnitride was studied by X-rays, electron diffraction and electron microscopy. V8N exists in two different modifications (α′ and α″). The vanadium sublattice of both phases is pseudo-tetragonal, in reality triclinic, with lattice parameters: , , αo = βo = 90.5o ± 0.1o, γo = 90o. The proposed unit cell of α′-V8N has dimensions: a = 2√2 ao, c = 2co and corresponds to V32N4. Doublets of nitrogen atoms occupy two sets of octahedral cavities whose shortest axes are aligned along the x and y directions of the sublattice in an ordered fashion. The α″-V8N phase is a periodically twinned modification of the α′-V8N, the twin plane being of the (001) type. The V8O suboxide has the same structure as the α″-V8N, the sublattice parameters being: , , αo = βo = 90.3o ± 0.1o, γo = 90o. 相似文献
16.
A series of isotypic silicates of composition RE2M[SiO4]2 (OH) with RE = La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, and M = Al3+, Fe3+ has been synthesized under hydrothermal conditions. Lattice constants of two members as determined from single crystal X-ray diffraction data are: La2Al[SiO4]2 (OH) (La2Fe[SiO4]2 (OH)) , , , gb = 112.4 (112.5°), , Z=4. 相似文献
17.
An oxygen-defect perovskite Sr2Mn2O5 was isolated by reduction of SrMnO3?x perovskites in the presence of zirconium. Its structure, similar to that of Ca2Mn2O5, has been determined by X-ray powder diffraction and HREM. The orthorhombic cell has the parameters : , , . The possible space groups are Pbam and Pba2. The framework is built up from corner-sharing MnO4 pyramids forming pseudo-hexagonal tunnes running along 〈001〉 and perovskite tunnels running along 〈110〉 and 〈110〉. This oxide is antiferromagnetic with and . 相似文献
18.
In copper doped Y2BaZnO5 oxides, copper exhibits a distorted square pyramidal coordination which is consistant with the values of g and A tensors obtained from O band ERS spectrum for a sample containing about 1 % Cu. Three values for g and A are observed, g1 = 2.0495, g2 = 2.0515, g3 = 2.275, , and . Since an approximate C4v point symmetry can be assumed for copper. The electronic spectrum shows three bands at 11700, 14500 and 20500 cm?1 which can be assigned to the transitions A1 → B1, B2 → B1 and E → B1 respectively. The orbital reduction parameters are calculated and the bonding covalency is discussed. 相似文献
19.
The crystallographic structure and interface oxidation state of thin ZnO films r.f. sputtered onto silicon and SiO2/Si substrates were investigated. The quality of the ZnO layers is characterized by a high optical transmission coefficient which is close to unity up to an optical band gap corresponding to that of single-crystal ZnO. The values of the transmission coefficients and band edge provide sensitive indicators of film quality. The deposited layers have a wurtzite crystal structure with lattice parameters and , corresponding closely with bulk ZnO. The orientation of the ZnO grains with respect to the substrate depends critically on the interface oxidation state. An analysis of X-ray photoelectron spectra provides an assessment of this interface oxidation state. 相似文献
20.
KHSO4 · KH2PO4 is monoclinic with Z = 2 and the following unit cell dimensions: a = 7.434(3); b = 7.341(3); ; β = 99.56(5)°.Crystal structure of this salt has been solved, using 1699 independent reflexions with a final R value: 0.034. PO4 and SO4 tetrahedra are randomly distributed in the arrangement with a resulting (P.S)-O mean distance of 1.508(3) Å. 相似文献