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1.
La mesure du nombre de transport ionique dans HfO2 et ZrO2 ae´te´re´alise´e entre 1300°C et 1600°C sous des pressions partielles d'oxyge`ne variant de 1 atma`10?10 atm. La contribution des porteurs ioniques ete´lectroniques dans la conductivite´totale du mate´riau est discute´e; pour HfO2, le de´sordre de Schottky rend compte des re´sultats; pour ZrO2 le ro?le des impurete´s apparait important.  相似文献   

2.
La phase α de type perovskiteBaFe1?xZnxO2,5?x/2 (0.05 < x < 0,40) pre´sente un ferrimagne´tisme faible pourx < 0,25, avecTc de l'ordre de 470°C, puis paramagne´tique (au-dessus de 77 K) pourx > 0,25, ce qui traduit la destruction progressive de l'ordre antiferromagne´tique observe´dans BaFeO2.5. Les phases β (Ba4Fe2Zn2O9) et γ (BaZn1?yFeyO2+y/2) sont en accord avec une forte perturbation du site octae´drique de la perovskite. La conductivite´est asseze´leve´e, de caracte`re mixte, avec une re´partition ionique-e´lectronique qui de´pend des conditions de synthe`se, et de la tempe´rature compte tenu dese´nergies d'activation diffe´rentes. Le coefficient de diffusion de l'oxyge`ne qui s'en de´duit este´leve´, mais le nombre de porteurs est restreint par la formation de paires de lacunes d'oxyge`ne tendant vers la coordinence 4 du fer.  相似文献   

3.
L'action de NH3 sur les germanates de lithium entre 680 et 800°C conduita`l'obtention d'une phase de formule Li1+xGe2?xN3?3xO3x avec0,04 ≤ x ≤ 0,33. Le compose´pour lequelx = 0,33ae´te´e´tudie´par diffraction de neutrons selon la me´thode du temps de vol et analyse de profil des raies de diffraction. La structure te´trae´drique normale de´rive de celle de la wurtzite (groupe spatialCmc21). Les atomes d'oxyge`ne et d'azote sont re´partis de fac¸on statistique sur les sites anioniques. On observe un ordre partiel des atomes de lithium et de germanium sur les sites cationiques en accord avec le calcul selon Pauling des forces de liaisons dirige´es.  相似文献   

4.
Un cristal de Fe7SiO10 a été isolé par J. Smuts, J. Steyn, et J. Boeyens (Acta Crystallogr. B25, 1251 (1969)), dans un réfractaire sidérurgique usagé, et appelé iscorite. Selon ces auteurs, la maille est monoclinique et la structure basée sur un empilement de blocs FeO et Fe3SiO6; mais le facteur d'accord est médiocre (R = 0,165) et les distances interatomiques très incorrectes. Nous avons donc préparé, pour la première fois, cette phase, et montré en combinant l'analyse chimique, la densité, l'étude aux rayons X du système FeSiO, et l'analyse d'un cristal à la microsonde, que la composition la plus correcte est Fe7(Si0.94Fe0.06)O10. L'étude d'un cristal confirme et précise la maille de Smuts et al.: monoclinique, avec a = 21,336(2), b = 3,0679(3), c = 5,8744(8)Å, β = 98°,06(1), P2m ou P21m. Cependant les diagrammes de Weissenberg présentent des lignes continues de diffusion pour certaines strates qui indiquent un désordre microstructural intense. Il en va de même pour la diffraction des électrons. Il n'est donc pas étonnant que l'affinement, sur la base du modèle de Smuts et al., ait donnéR = 0,09 dans l'un ou l'autre groupe d'espace. Les mesures magnétiques conduisent à un paramagnétisme avec forte contribution orbitale pour Fe2+, et mise en ordre vers 250 K avec, en-dessous, un comportement de ferromagnétique faible. Contrairement à la wüstite, l'iscorite ne se dismute pas facilement; elle donne avec Fe9PO12 des solutions solides limitées.A crystal of Fe7SiO10 has been isolated by J. Smuts, J. Steyn, and J. Boeyens (Acta Crystallogr. B25, 1251 (1969)), from a furnace refractory brick, and has been called iscorite. According to these authors, the cell is monoclinic and the structure based upon a stacking of FeO and Fe3SiO6 blocks; however the reliability factor is poor (R = 0.165) and the interatomic calculated distances are not correct. Therefore, we have prepared this phase for the first time; combining chemical analysis, density measurements, X-ray investigation of the FeSiO system, and electron probe microanalysis of a crystal, we have shown that the correct composition is Fe7(Si0.94Fe0.06)O10. The crystal study confirms, with a higher accuracy, the parameters for the cell proposed by Smuts et al.: a = 21.336(2), b = 3.0679(3), c = 5.8744(8)Å, β = 98°.06(1), P2m or P21m. However, the Weissenberg patterns display continuous diffusion lines, indicating an intense microstructural disorder, in agreement with the electron diffraction patterns. Hence it is not surprising to obtain, on the basis of the Smuts et al. model, a value R = 0.09 with both space groups. The magnetic measurements indicate a paramagnetism with strong orbital Fe2+ contribution and a transition at ~250 K to an ordered magnetic state, with a weak ferromagnetism below 250 K. In contrast to the case of wustite, iscorite does not easily disporportionate; it forms limited solid solutions with Fe9PO12.  相似文献   

5.
Subsolidus phase relations in the systems Li2MoO4-K2MoO4-Ln2(MoO4)3 (Ln=La, Nd, Dy, Er) were determined. Formation of LiKLn2(MoO4)4 was confirmed in the systems with Ln=Nd, Dy, Er at the LiLn(MoO4)2-KLn(MoO4)2 joins. No intermediate phases of other compositions were found. No triple molybdates exist in the system Li2MoO4-K2MoO4-La2(MoO4)3. The join LiLa(MoO4)2-KLa(MoO4)2 is characterized by formation of solid solutions.Triple molybdates LiKLn2(MoO4)4 for Ln=Nd-Lu, Y were synthesized by solid state reactions (single phases with ytterbium and lutetium were not prepared). Crystal and thermal data for these molybdates were determined. Compounds LiKLn2(MoO4)4 form isostructural series and crystallized in the monoclinic system with the unit cell parameters a=5.315-5.145 Å, b=12.857-12.437 Å, c=19.470-19.349 Å, β=92.26-92.98°. When heated, the compounds decompose in solid state to give corresponding double molybdates. The dome-shaped curve of the decomposition temperatures of LiMLn2(MoO4)4 has the maximum in the Gd-Tb-Dy region.While studying the system Li2MoO4-K2MoO4-Dy2(MoO4)3 we revealed a new low-temperature modification of KDy(MoO4)2 with the triclinic structure of α-KEu(MoO4)21 (a=11.177(2) Å, b=5.249(1) Å, c=6.859(1) Å, α=112.33(2)°, β=111.48(1)°, γ=91.30(2)°, space group , Z=2).  相似文献   

6.
Physicochemical analysis (XRPA, DTA) was used to study phase equilibria in a ternary salt system Rb2MoO4-Fe2(MoO4)3-Hf(MoO4)2 in the subsolidus region. Ternary molybdates with compositions 5:1:3, 5:1:2, and 1:1:1 have been found and synthesized. Crystal and thermal characteristics have been determined. Single crystals of the ternary molybdate Rb5FeHf(MoO4)6 with a composition of 5:1:2 were grown. The crystal structure of the compound was solved using X-ray diffractometry (CAD-4 automatic diffractometer, MoK α radiation, 1766 F(hkl), R = 0.0298). Hexagonal crystals with unit cell dimensions: a = b = 10.124(1) Å, c =15.135(3) Å, V = 1343.4(4) Å3, Z = 2, ρcalc = 4.008 g/cm3, space group P63. The mixed three-dimensional framework of the structure is formed from two sorts of MoO4 tetrahedra and Fe and Hf octahedra linked through their common O-vertices. Rubidium atoms of three varieties occupy the large voids of the framework.Original Russian Text Copyright © 2004 by B. G. Bazarov, R. F. Klevtsova, A. D. Tsyrendorzhieva, L. A. Glinaskaya, and Zh. G. Bazarova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1038–1043, November–December, 2004.  相似文献   

7.
Proton NMR relaxation times (T2, T1, T1?) are reported for powder samples of MoO3 · 2H2O and yellow MoO3 · H2O in the temperature range 150–325 K and at 20 and 60 MHz. No translation of hydrogen atoms is detected but the spin-lattice relaxation behavior indicates reorientation of H2O molecules. The waters coordinated to Mo atoms undergo 180° flips (about their C2 axes) with similar motional parameters in both compounds. The interlayer waters in MoO3 · 2H2O undergo 180° flips with different parameters. An assumed Arrhenius-type temperature dependence of correlation times leads to preexponential factors which are “anomalously” low. The possible involvement of temperature-dependent activation barriers is discussed.  相似文献   

8.
Two new mixed organic-inorganic uranyl molybdates, (C6H14N2)3[(UO2)5(MoO4)8](H2O)4 (1) and (C2H10N2)[(UO2)(MoO4)2] (2), have been obtained by hydrothermal methods. The structure of 1 [triclinic, , Z=1, a=11.8557(9), b=11.8702(9), c=12.6746(9) Å, α=96.734(2)°, β=91.107(2)°, γ=110.193(2)°, V=1659.1(2) Å] has been solved by direct methods and refined on the basis of F2 for all unique reflections to R1=0.058, which was calculated for the 5642 unique observed reflections (|Fo|?4σF). The structure contains topologically novel sheets of uranyl square bipyramids, uranyl pentagonal bipyramids, and MoO4 tetrahedra, with composition [(UO2)5(MoO4)8]6−, that are parallel to (−101). H2O groups and 1,4-diazabicyclo [2.2.2]-octane (DABCO) molecules are located in the interlayer, where they provide linkage of the sheets. The structure of 2 [triclinic, , Z=2, a=8.4004(4), b=11.2600(5), c=13.1239(6) Å, α=86.112(1)°, β=86.434(1)°, γ=76.544(1)°, V=1203.14(10) Å] has been solved by direct methods and refined on the basis of F2 for all unique reflections to R1=0.043, which was calculated for 5491 unique observed reflections (|Fo|?4σF). The structure contains topologically novel sheets of uranyl pentagonal bipyramids and MoO4 tetrahedra, with composition [(UO2)(MoO4)2]2−, that are parallel to (110). Ethylenediamine molecules are located in the interlayer, where they provide linkage of the sheets. All known topologies of uranyl molybdate sheets of corner-sharing U and Mo polyhedra can be described by their nodal representations (representations as graphs in which U and Mo polyhedra are given as black and white vertices, respectively). Each topology can be derived from a simple black-and-white graph of six-connected black vertices and three-connected white vertices by deleting some of its segments and white vertices.  相似文献   

9.
La structure destrans fe´ruloyl-6′ ettrans sinapoyl-6′ lyaloside, isole´s des feuilles dePauridiantha Lyalii, ae´te´de´termine´e par de´gradation chimique et par spectroscopie (Masse, RMN1H et13C). Ces compose´s font partie d'un groupe structural caracte´rise´par un enchai?nement alcaloide-monoterpe`ne-ose-acide (C6-C3), groupe dont un seul repre´sentant semble avoire´te´isole´jusqu'a`pre´sent. Leur fonction dans le ve´ge´tal est discute´e.  相似文献   

10.
Au sein d'un re´seau de type BaFeF5 des chai?nes d'octae`dres fluore´sa`sommets communs peuvent disparai?tre en donnant naissance a des canaux dont l'occupation partielle ou totale par des files de cations Sr2+ et de couples d'anions F?, conduit respectivement aux phases Sr3(FeF6)2 ou Sr5T3F19 (T = Cr, Co, Ga). Une discussion cristallochimique permet d'expliquer l'existence d'un domaine de solutions solides au sein du diagramme ternaire SrF2BaF2FeF3.  相似文献   

11.
Crystals of the rhenium cluster complex (H3O)4[(C2H5)4N]6[Th2Cl4(H2O)12O]3[Re4Se4(CN)12]4 are obtained in an acidic (HCl) aqueous solution by the reaction of cluster salt K4[Re4Se4(CN)12]·6H2O with ThCl4 and (C2H5)4NCl. Single crystal X-ray analysis shows that the title compound is ionic and crystallizes in the cubic crystal system (a = 22.7322(3) ?, V = 11746.93(27) ?3, Z = 2, I4 3m space group, R = 0.0350). It contains [Th2Cl4(H2O)12O]2+ cations with two thorium atoms bonded to each other through the bridging oxygen atom forming an angle of 180° in the structure.  相似文献   

12.
A cobalt phosphonate (H3O)6·[Co4(H2O)4(HPMIDA)2(PMIDA)2)]·2H2O, 1, has been synthesized from a mild solvothermal reaction of Co(II) ion with N-(phosphonomethyl)iminodiacetic acid (H4PMIDA). Compound 1 crystallizes in the triclinic space group with cell parameters of , , , α=93.06(3)°, β=99.66(3)°, γ=90.34(3)° and Z=1. Compound 1 shows a novel tetra-nuclear molecular structure. In the crystal lattice, molecules of 1 hydrogen bond to each other to form two-dimensional (2D) layers, which are further linked together by the co-crystallized H2O molecules and H3O+ counter ions through hydrogen bonding to form the 3D supramolecular network. Thermogravimetric analysis, IR spectrum, magnetic susceptibility and luminescent spectra are given.  相似文献   

13.
Flower-like NaY(MoO4)2 particles were synthesized through a microwave-assisted hydrother-mal process followed by a subsequent calcination process. The products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron mi-croscopy. The possible formation mechanism of the flower-like NaY(MoO4)2 precursor was proposed. The NaY(MoO4)2:Eu3+ phosphors were also prepared and their luminescence properties showed the NaY(MoO4)2:Eu3+ materials with the emission peak at 612 nm had potential application as a red phosphor for white light-emitting diodes. Furthermore, the microwave-assisted hydrothermal process followed by a subsequent calcination process could be extended to prepare the other lanthanide molybdates with the flower-like morphology.  相似文献   

14.
The first organically templated 3d-4f mixed metal sulfates, [H2en]2{La2M(SO4)6(H2O)2} (M=Co 1, Ni 2) have been synthesized and structurally determined from non-merohedrally twinned crystals. The two compounds are isostructural and their structures feature a three-dimensional anionic network formed by the lanthanum(III) and nickel(II) ions bridged by sulfate anions. The La(III) ions in both compounds are 10-coordinated by four sulfate anions in bidentate chelating fashion, and two sulfate anions in a unidentate fashion. The transition metal(II) ion is octahedrally coordinated by six oxygens from four sulfate anions and two aqua ligands. The doubly protonated enthylenediamine cations are located at the tunnels formed by 8-membered rings (four La and four sulfate anions).  相似文献   

15.
Crystal structures of Pb(MoO2)2(PO4)2 and Ba(MoO2)2(PO4)2 were determined. Both compounds contain the molybdyl group MoO2. The monoclinic unit-cell parameters are a = 6.353(7), b = 12.289(4), c = 11.800 Å, β = 92°56(6), and Z = 4 for the lead salt and a = 6.383(8), b = 7.142(7), c = 9.953(8) Å, β = 95°46(8), and Z = 2 for the barium salt. P21c is the common space group. The R values are respectively R = 0.027 and R = 0.031 for 1964 and 1714 independent reflections. The frameworks built up by a three-dimensional network of monophosphate PO4 and molybdyl MoO2 groups are similar, characterized mainly by corner-sharing PO4 and MoO6 polyhedra. Two oxygen atoms of each MoO6 group are bonded to the molybdenum atom only as in other molybdyl salts.  相似文献   

16.
Two new vanadium squarates have been synthesized, characterized by infrared and thermal behavior and their structures determined by single crystal X-ray diffraction. Both structures are made of discrete, binuclear vanadium entity but in 1, [V(OH)(H2O)2(C4O4)]2·2H2O the vanadium atom is trivalent and the entity is neutral while in 2, (NH4)[(VO)2(OH)(C4O4)2(H2O)3]·3H2O, the vanadium atom is tetravalent and the entity is negatively charged, balanced by the presence of one ammonium ion. Both molecular anions are bridged by two terminal μ2 squarate ligands. 1 crystallizes in the triclinic system, space group P-1, with lattice constants a=7.5112(10) Å, b=7.5603(8) Å, c=8.2185(8) Å, α=106.904(8)°, β=94.510(10)°, γ=113.984(9)° while 2 crystallizes in the monoclinic system, space group C2/c, with a=14.9340(15) Å, b=6.4900(9) Å, c=17.9590(19) Å and β=97.927(12)°. From the magnetic point of view, V(III) binuclear species show ferromagnetic interactions at low temperatures. However, no anomalies pointing to magnetic ordering are observed down to 2 K.  相似文献   

17.
The subsolidus area of Cs2MoO4-Al2(MoO4)3-Zr(MoO4)2 system was studied by X-ray powder diffraction. Two new molybdates with component molar ratios of 1: 1: 1 (S1) and 5:1:2 (S2) were synthesized for the first time. The crystallographic parameters of the 5:1:2 compound were determined. Solution- melt crystallization and spontaneous nucleation yielded crystals of new 1:1:1 cesium aluminum zirconium molybdate Cs(AlZr0.5)(MoO4)3. Its formula unit and crystal structure were refined by X-ray diffraction (1592 reflections, R=0.0249). Trigonal crystals: a=12.9441(2) ?, c=12.0457(4) ?, V=1747.86(7) ?3, Z = 6, space group R $ \bar 3 $ \bar 3 . The three-dimensional combined framework of this structure is formed by MoO4 tetrahedrons linked through common vertices to (Al,Zr)O6 octahedrons. Cesium atoms occupy large cavities of the framework. Crystallographic position M(1) is occupied by randomly distributed Al3+ and Zr4+ cations.  相似文献   

18.
Crystals with uncommon composition NaBa6[Co(Edta)]4(ClO4)9 · 30H2O (Edta4− is ethylenediaminetetraacetic acid anion) were obtained with the following unit cell parameters: a = 14.8513(9) Å, b = 26.2361(15) Å, c = 15.1789(9) Å, α = 91.661(7)°, β = 113.035(7)°, γ = 89.897(7)°, space group P1¯. Each complex anion [Co(Edta)] is bonded through the carboxyl O atoms to five Ba atoms to give three-dimensional framework in a crystal. One perchlorate ion forms Ba-O-Cl-O-Ba bridge between the Ba atoms; four ClO 4 ions are isolated, while the remaining four ions act as monodentate ligands at the Ba atoms. The water molecules (25 in sum) complete the coordination sphere of the Ba atoms to eight-, nine-, or ten-vertex polyhedron. Four water molecules are in the closest surrounding of the Na atom, one H2O molecule is isolated.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 590–595.Original Russian Text Copyright © 2005 by Zabel, Poznyak, Pawlowski.  相似文献   

19.
Three new hydrated scandium selenites have been hydrothermally synthesized as single crystals and structurally and physically characterized. Sc2(SeO3)3·H2O crystallizes as a new structure type containing novel ScO7 pentagonal bipyramidal and ScO6+1 capped octahedral coordination polyhedra. Sc2(SeO3)3·3H2O contains typical ScO6 octahedra and is isostructural with its M2(SeO3)3·3H2O (M=Al, Cr, Fe, Ga) congeners. CsSc3(SeO3)4(HSeO3)2·2H2O contains near-regular ScO6 octahedra and has essentially the same structure as its indium-containing analogue. All three phases contain the expected pyramidal [SeO3]2- selenite groups. Crystal data: Sc2(SeO3)3·3H2O, Mr=524.85, trigonal, R3c (No. 161), , , , Z=6, R(F)=0.018, wR(F2)=0.036; Sc2(SeO3)3·H2O, Mr=488.82, orthorhombic, P212121 (No. 19), , , , , Z=4, R(F)=0.051, wR(F2)=0.086; CsSc3(SeO3)4(HSeO3)2·2H2O, Mr=1067.60, orthorhombic, Pnma (No. 62), , , , , Z=4, R(F)=0.035, wR(F2)=0.070.  相似文献   

20.
Electrical conductivities were measured for the ternary systems Y(NO3)3+La(NO3)3+H2O, La(NO3)3+Ce(NO3)3+H2O, La(NO3)3+Nd(NO3)3+H2O, and their binary subsystems Y(NO3)3+H2O, La(NO3)3+H2O, Ce(NO3)3+H2O, and Nd(NO3)3+H2O at (293.15, 298.15 and 308.15) K. The measured conductivities were used to test the generalized Young’s rule and the semi-ideal solution theory. The comparison results show that the generalized Young’s rule and the semi-ideal solution theory can yield good predictions for the conductivities of the ternary electrolyte solutions, implying that the conductivities of aqueous solutions of (1:3 + 1:3) electrolyte mixtures can be well predicted from those of their constituent binary solutions by the simple equations.  相似文献   

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