共查询到20条相似文献,搜索用时 15 毫秒
1.
Mourad Hidouri Alain Wattiaux Jacques Darriet 《Journal of solid state chemistry》2006,179(6):1808-1813
Single crystals of a new mixed-valent iron phosphate Na1/2Cu4/3Fe2(PO4)3 have been synthesized by a flux method and structurally characterized from X-ray diffraction data. Crystal data: space group ; ; ; ; α=105.881(1)°; β=107.202(1)°; γ=101.467(1)°; Z=2; R1=0.03; wR2=0.093. The three-dimensional structure was found to be closely related to that of the well known Howardevansite structural type. It results from infinite chains of CuO5 and FeO6 polyhedra, joined together by (Cu,□)O6 octahedra and PO4 tetrahedra by corner-sharing. The large cavities in framework are occupied by Na+ ions. The magnetic susceptibility study revealed an antiferromagnetic behavior with Neel temperature of approximately 40 K. The Mössbauer spectroscopy confirmed the presence of iron in both +2 and +3 oxidation states. 相似文献
2.
Mourad Hidouri Alain Wattiaux Léopold Fournés Jacques Darriet Mongi B. Amara 《Comptes Rendus Chimie》2011,14(10):904-910
Na2Mn2(1 − x)Cd2xFe(PO4)3 (0 ≤ x ≤ 1) phosphates were prepared by solid state reaction and characterized by powder X-ray diffraction, magnetic susceptibility and Mössbauer spectroscopy. The X-ray diffraction patterns indicated the formation of a continuous solid solution which crystallizes in the alluaudite structural type characterized by the general formula X(2)X(1)M(1)M(2)2(PO4)3. The cation distribution, deduced from a structure refinement of the x = 0, 0.5 and 1 compositions, is ordered in the X(2) sites and disordered in the remaining X(1), M(1) and M(2) sites. The magnetic susceptibility study revealed an antiferromagnetic behaviour of the studied compounds. The 57Fe Mössbauer spectroscopy confirmed the structural results and proved the exclusive presence of Fe3+ ions. 相似文献
3.
Abdessalem Badri María Luisa López Alain Wattiaux 《Journal of solid state chemistry》2011,184(4):937-944
Single crystals of a new phosphate KCuFe(PO4)2 have been prepared by the flux method and its structural and physical properties have been investigated. This compound crystallizes in the monoclinic system with the space group P21/n and its parameters are: a=7.958(3) Å, b=9.931(2) Å, c=9.039(2) Å, β=115.59(3)° and Z=4. Its structure consists of FeO6 octahedra sharing corners with Cu2O8 units of edge-sharing CuO5 polyhedra to form undulating chains extending infinitely along the b-axis. These chains are connected by the phosphate tetrahedra giving rise to a 3D framework with six-sided tunnels parallel to the [101] direction, where the K+ ions are located. The Mössbauer spectroscopy results confirm the exclusive presence of octahedral Fe3+ ions. The magnetic measurements show the compound to be antiferromagnetic with Cm=5.71 emu K/mol and θ=−156.5 K. The derived experimental effective moment μex=6.76μB is somewhat higher than the theoretical one of μth=6.16μB, calculated taking only into account the spin contribution for Fe3+ and Cu2+ cations. Electrical measurements allow us to obtain the activation energy (1.22 eV) and the conductivity measurements suggest that the charge carriers through the structure are the potassium cations. 相似文献
4.
S. Benmokhtar A. El Jazouli P. Gravereau L. Fournès D. Waal 《Journal of solid state chemistry》2006,179(12):3709-3717
A new iron titanyl oxyphosphate Fe0.50TiO(PO4) was synthesized by both solid-state reaction and Cu2+-Fe2+ ion exchange method. The material was then characterized by X-ray diffraction, Mössbauer spectroscopy, magnetic susceptibility measurements and Raman spectroscopy. The crystal structure of the compound was refined, using X-ray powder diffraction data, by Rietveld profile method; it crytallizes in the monoclinic system, space group P21/c (No.14), with , , , β=120.36°(1), and Z=4. The volume of the title compound is comparable to those of the M0.50IITiO(PO4) series, where MII=Mg, Co, Ni and Zn. The framework is built up from [TiO6] octahedra and [PO4] tetrahedra. [TiO6] octahedra are linked together by corners and form infinite chains along the c-axis. Ti atoms are displaced from the center of octahedral units showing an alternating short distance (1.73 Å) and a long one (2.22 Å). These chains are linked together by [PO4] tetrahedra. Fe2+ cations occupy a triangle-based antiprism sharing two faces with two [TiO6] octahedra. Mössbauer and magnetic measurements show the existence of iron only in divalent state, located exclusively in octahedral sites with high spin configuration (t2g4eg2). Raman study confirms the existence of Ti-O-Ti chains. 相似文献
5.
S. Benmokhtar A. El Jazouli J.P. Chaminade A. Wattiaux J.C. Grenier 《Journal of solid state chemistry》2007,180(7):2004-2012
A new iron titanyl phosphate Fe0.50Ti2(PO4)3 was synthesized by both solid-state reaction and Cu2+-Fe2+ ion exchange method. The material was then characterized by X-ray diffraction, Mössbauer, magnetic susceptibility measurements and optical absorption. The crystal structure of the compound was refined, using X-ray powder diffraction data, by the Rietveld profile method; it crystallizes in the rhombohedral system, space group , with a=8.511(1) Å and c=20.985(3) Å, V=1316.45(3) Å3 and Z=6. The structure, which is compared to that of Mn0.50Ti2(PO4)3 is built up from [TiO6] octahedra and [PO4] tetrahedra which are linked by corner sharing along the c-axis. Fe2+ cations are located in half of the antiprism MI sites and are orderly distributed with vacancies within the two possible positions of the MI sites of . These results were supported by the Mössbauer studies that showed the presence of one Fe2+ site in the high spin state (t2g4eg2). The Curie-Weiss-type behavior is observed in the magnetic susceptibility. Diffuse reflectance spectrum indicates the presence of octahedrally coordinated Fe2+ ions. 相似文献
6.
Yoshitaka Misawa 《Journal of solid state chemistry》2011,184(6):1478-1483
Structures and magnetic properties of double perovskite-type oxides Eu2LnTaO6 (Ln=Eu, Dy-Lu) were investigated. These compounds adopt a distorted double perovskite structure with space group P21/n. Magnetic susceptibility, specific heat, and 151Eu Mössbauer spectrum measurements show that the Eu2+ ions at the 12-coordinate sites of the perovskite structure are antiferromagnetically ordered at ∼4 K, and that Ln3+ ions at the 6-coordinate site are in the paramagnetic state down to 1.8 K. 相似文献
7.
151Eu and 121Sb Mössbauer spectroscopy of EuSbSe3 and EuBiSe3 were measured at different temperatures. The presence of divalent europium and trivalent antimony were confirmed. The largely negative values of the isomer shift in 151Eu spectrum show highly ionic bonding within these two compounds. Both of them show magnetic hyperfine field splitting at 4.2 K, which indicates a change in the orientation of the EFG principal axis with respect to the magnetic hyperfine field direction. EuSbSe3 has slightly smaller electron density at the antimony nuclei, compared to Sb2Se3. 相似文献
8.
V. A. Morozov B. I. Lazoryak A. P. Malakho K. V. Pokholok S. N. Polyakov T. P. Terekhina 《Journal of solid state chemistry》2001,160(2):377
The double sodium and iron phosphate Na3Fe(PO4)2 was synthesized and studied by the XRD method, the second harmonic generation technique, and Mössbauer and IR spectroscopy. The compound crystallizes into a monoclinic system (space group C2/c) with unit cell parameters a=9.0736(2) Å, b=5.0344(1) Å, c=13.8732(3) Å, β=91.435(2)° and is found to be related to the K3Na(SO4)2 structure type. The crystal structure was determined by Rietveld analysis (Rwp=5.86, RI=2.03). Iron cations occupy the M (Na) position while sodium cations occupy the X (K) and Y (K) positions of the glaserite-like structure. Mössbauer spectroscopy shows the presence of high-spin Fe3+ in octahedral coordination. 相似文献
9.
The Li1.746Nd4.494FeO9.493 (LNF) ternary phase, located in the Li2O-rich part of the Li2O-Nd2O3-Fe2O3 system, crystallizes with a cubic unit cell of dimension and the space group Im3m. Refinement on F resulted in R=1.9%. The structure is comprised of a network of corners, edges and faces sharing the coordination polyhedra of neodymium. In between this skeleton the regular octahedra of oxygen-coordinated iron and trigonal prisms of lithium are located. The Mössbauer spectra revealed the presence of Fe3+, Fe4+ and Fe5+ ions distributed on two symmetry-independent lattice positions. 相似文献
10.
Metal valences in electron-doped (Sr,La)2FeTaO6 double perovskite: A Fe Mössbauer spectroscopy study
Substitution of divalent Sr by trivalent La is found to affect the valence states of both of the two B-site cations, Fe and Ta, in the double perovskite oxide (Sr1−xLax)2FeTaO6. Moreover, it improves the degree of order of these cations. From 57Fe Mössbauer spectra the average Fe valence was found to decrease with increasing La substitution level, x. However, the valence of Fe decreased less than expected if the valence of Ta was assumed to remain constant. Hence, we conclude that also the valence of Ta decreases. 相似文献
11.
Fumito Furuuchi 《Journal of solid state chemistry》2004,177(11):3853-3858
Ternary europium copper sulfide Eu2CuS3 have been investigated by X-ray diffraction, 151Eu Mössbauer spectroscopy, magnetic susceptibility, magnetization, and specific heat measurements. In this compound, Eu2+ and Eu3+ ions occupy two crystallographically independent sites. The 151Eu Mössbauer spectra indicate that the Eu2+ and Eu3+ ions exist in the molar ratio of 1:1, and the Debye temperatures of Eu2+ and Eu3+ are 180 and 220 K, respectively. In its magnetic susceptibility, the divergence between the zero-field cooled and field cooled susceptibilities appears below 3.4 K. The specific heat has a λ-type anomaly at the same temperature. From the field dependence of magnetization at 1.8 K, the Eu2+ ion was found to be in the ferromagnetic state with the saturation magnetization MS=6.7 μB. 相似文献
12.
57Fe doped La4Ni2.97Fe0.03O9.95 was synthesized by a citrate method and, afterwards, successfully oxidized and reduced by electrochemical methods. The compounds obtained were investigated by X-ray diffraction, electrical measurements and Mössbauer spectroscopy. The study allowed to follow the variation of the two nickel sites environment with the oxygen stoichiometry and a deeper understanding of the electrical behavior versus oxygen non-stoichiometry was achieved. The Mössbauer study revealed that after both oxidation and reduction treatments, the major modifications were observed on the octahedra adjacent to the La2O2 layers, while the middle octahedra of the triple perovskite block remained almost unchanged. The oxygen intercalation (oxidized treatment) takes place essentially in the La2O2 layers and the oxygen desintercalation (reduction treatment) occurs in the octahedral sites adjacent to those layers. 相似文献
13.
Aintzane Goñi José Luis Pizarro Alain Wattiaux María Isabel Arriortua 《Journal of solid state chemistry》2006,179(1):81-90
Mössbauer spectroscopy and neutron diffraction studies have been carried out for the α-Li3Fe2(PO4)3−x(AsO4)x (x=1, 1.5, 2, 3) solid solution, potential candidate for the cathode material of the lithium secondary batteries. The crystal and magnetic structures of all these phases are based on the structural and magnetic model corresponding to the α-Li3Fe2(PO4)3 phosphate parent, but with some differences promoted by the arsenate substitution. The PO4 and AsO4 groups have a random distribution in the structure. In all compounds the coupling of the magnetic moments takes place in the (001) plane, but the value of the angle between the moments and the x direction decreases from 38.3° (α-Li3Fe2(AsO4)3) to 4.7° (α-Li3Fe2(PO4)2(AsO4)1). This rotation arises from the change in the tilt angle between the Fe(1)O6 and Fe(2)O6 crystallographically and magnetically independent octahedra in the structures, and affects the effectiveness of the magnetic exchange pathways. The ordering temperature TN decreases with the increase of phosphate amount in the compounds. The existence of a phenomenon of canting and the evolution of the ferrimagnetic behavior in this solid solution is also discussed. 相似文献
14.
I.A. Leonidov J.A. Bahteeva D.S. Filimonov V.L. Kozhevnikov 《Journal of solid state chemistry》2006,179(10):3045-3051
High-temperature electrical conductivity measurements, structural data from powder X-ray diffraction and 57Fe Mössbauer spectroscopy were combined to study the interrelationship of oxygen ion transport and p- and n-type transport in Sr2(Fe1−xGax)2O5, where x=0, 0.1 and 0.2. Although gallium substitution generally decreases the total ion-electron transport, the transition of the orthorhombic brownmillerite structure to a cubic phase on heating results in the recurrence of the conductivity to the same high level as in the parent ferrite (x=0). The changes of the partial contributions to the total conductivity as a function of x are shown to reflect a complicated interplay of the disordering processes that develop in the oxygen sublattice on heating in response to replacement of iron with gallium. 相似文献
15.
Siân E. Dutton Fernande Grandjean Moulay T. Sougrati Emma Winstone 《Journal of solid state chemistry》2009,182(7):1638-5922
A polycrystalline sample of Pr18Li8Fe4RuO39 has been synthesized by a solid state method and characterized by neutron powder diffraction, magnetometry and Mössbauer spectroscopy; samples of Pr18Li8Fe5−xMnxO39 and Pr18Li8Fe5−xCoxO39 (x=1, 2) have been studied by magnetometry. All these compounds adopt a cubic structure (space group , a0∼11.97 Å) based on intersecting 〈111〉 chains made up of alternating octahedral and trigonal-prismatic coordination sites. These chains occupy channels within a Pr-O framework. The trigonal-prismatic site in Pr18Li8Fe4RuO39 is occupied by Li+ and high-spin Fe3+. The remaining transition-metal cations occupy the two crystallographically-distinct octahedral sites in a disordered manner. All five compositions adopt a spin-glass-like state at 7 K (Pr18Li8Fe4RuO39) or below. 相似文献
16.
Jian Qiao 《Journal of solid state chemistry》2009,182(7):1929-1934
A new open-framework iron (III) phosphite |C4N3H14|[Fe3(HPO3)4F2(H2O)2] has been solvothermally synthesized by using diethylenetriamine (DETA) as the structure-directing agent. Single-crystal X-ray diffraction analysis reveals that the compound crystallizes in the monoclinic space group C2/c having unit cell parameters a=12.877(3) Å, b=12.170(2) Å, c=12.159(2) Å, β=93.99(3)°, V=1900.9(7) Å3, and Z=4 with R1=0.0447, wR2=0.0958. The complex structure consists of HPO3 pseudo-tetrahedra and {Fe3O14F2} trimer building units. The assembly of these building units generates 3D inorganic framework with intersecting 6-, 8-, and 10-ring channels. The DETA cations are located in the 10-ring channels linked by hydrogen bonds. The Mössbauer spectrum shows that there exhibit two crystallographically independent iron (III) atoms. And the magnetic investigation shows the presence of antiferromagnetic interactions. Further characterization of the title compound was performed using X-ray powder diffraction (XRD), infrared (IR) spectra, thermal gravimetric analyses (TGA), inductively coupled plasma (ICP) and elemental analyses. 相似文献
17.
《Journal of solid state chemistry》2004,177(8):2705-2713
The (C2H10N2)[Fe3(HPO3)4] compound has been synthesized by using mild hydrothermal conditions under autogeneous pressure and the ethylenediamine molecule as templating agent. The compound crystallizes in the triclinic space group with unit-cell parameters a=5.416(1), b=5.416(1), c=13.977(2) Å, α=80.64(2), β=85.25(1), γ=60.03(1)° and Z=1. The final R-factors were R1=0.053 [wR2=0.092]. The crystal structure is constructed of layers stacked along the c-axis. The sheets contain FeO6 octahedra linked by (HPO3)2− phosphite oxoanions to give rise to Fe3O12 trimeric units sharing faces. The IR spectrum shows the characteristic bands of the phosphite and ethylenediammonium ions. From the diffuse reflectance spectrum, the Dq parameter of 805 cm−1 has been calculated for the iron(II) cation in slightly distorted octahedral geometry. The Mössbauer spectrum exhibits two doublets characteristic of two crystallographically independent iron(II) ions in octahedral symmetry. Magnetic measurements indicate the existence of antiferromagnetic interactions. 相似文献
18.
The alkali sodium ferrate (IV) Na4FeO4 has been prepared by solid-state reaction of sodium peroxide Na2O2 and wustite Fe1−xO, in a molar ratio Na/Fe=4, at 400°C under vacuum. Powder X-ray and neutron diffraction studies indicate that Na4FeO4 crystallizes in the triclinic system P−1 with the cell parameters= a=8.4810(2) Å, b=5.7688(1) Å, c=6.5622(1) Å, α=124.662(2)°, β=98.848(2)°, γ=101.761(2)° and Z=2. Na4FeO4 is isotypic with the other known phases Na4MO4 (M=Ti, Cr, Mn, Co and Ge, Sn, Pb). The solid solution Na4FexCo1−xO4 exists for x=0-1 and we have followed the evolution of the cell parameters with x to determine the lattice parameters of the triclinic cell of Na4FeO4. A three-dimensional network of isolated FeO4 tetrahedra connected by Na atoms characterizes the structure. This compound is antiferromagnetic below TN=16 K. At 2 K the magnetic cell is twice the nuclear cell and the magnetic structure is collinear (μFe=3.36(12) μB at 2 K). This black compound is highly hygroscopic. In water or on contact with the atmospheric moisture it is disproportionated in Fe3+ and Fe6+. The Mössbauer spectra of Na4FeO4 are fitted with one doublet (δ=− 0.22 mm/s, Δ=0.41 mm/s at 295 K) in the paramagnetic state and with a sextet at 8K. These parameters characterize Fe4+ high-spin in tetrahedral FeO4 coordination. 相似文献
19.
J. Prado-Gonjal D. Ávila M.E. Villafuerte-Castrejón F. González-García L. Fuentes R.W. Gómez J.L. Pérez-Mazariego V. Marquina E. Morán 《Solid State Sciences》2011,13(11):2030-2036
Multiferroic BiFeO3 has been rapidly synthesized by a microwave – hydrothermal method using nitrates as the metallic source. Structural characterization was performed by thermal analysis, X-ray diffraction and transmission electron microscopy. Generally accepted trigonal space group R3c, as well as recently suggested monoclinic symmetries, were assayed in the search for the best fit. Due to the ambiguity of the Rietveld refinement to distinguish between crystal systems, a micro-diffraction and HRTEM study has been performed. The best solution was obtained with the trigonal model. The room-temperature Mössbauer spectra reveal the presence of a small fraction (2%) of iron in low spin configuration. 相似文献
20.
Nanosize nickel-substituted cobalt ferrites were prepared using aerosol route and characterized by TEM, XRD, magnetic and Mössbauer spectroscopy. The particle size of as obtained samples was found to be ∼10 nm which increases upto ∼80 nm on annealing at 1200 °C. The unit cell parameter ‘a’ decreases linearly with the nickel concentration due to smaller ionic radius of nickel. The saturation magnetization for all the samples after annealing at 1200 °C lies in the range 47.6-84.5 emu/g. Room temperature Mössbauer spectra of as obtained samples exhibit a broad doublet, suggesting super paramagnetic nature of the sample. The broad doublet is further resolved into two doublets corresponding to the iron atoms residing at the surface and internal regions of the particle. The samples annealed at 1200 °C showed broad sextet, which is resolved into two sextets, corresponding to tetrahedrally and octahedrally coordinated Fe cations. Cation distribution calculated using XRD and Mössbauer data indicates a decrease in Fe3+(oct.)/Fe3+(tet.) ratio with increasing nickel concentration. 相似文献