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Journal of Solid State Chemistry (v.179, #1)
New open-framework three-dimensional lanthanide oxalates containing as a template the diprotonated 1,2- or 1,3-diaminopropane by A. Mohanu; C. Brouca-Cabarrecq; J.C. Trombe (pp. 3-17).
Single crystals of three new open-framework lanthanide oxalates have been synthesized hydrothermally, in the presence of 1,2-diaminopropane, (C3N2H12)[Nd(H2O)(C2O4)2]2·3H2OI and (C3N2H12)[Yb(C2O4)2]2·5H2OII, or 1,3-diaminopropane (C3N2H12)2[La2(C2O4)5]·5H2OIII. Their structures have been determined by X-ray diffraction data:I andIII crystallize in the triclinic system, space group P-1, witha=7.8130(5)Å,b=11.8800(6)Å,c=12.9940(8)Å,α=93.092(5)°,β=93.930(6)°,γ=108.359(5)° anda=11.6650(9)Å,b=11.9240(6)Å,c=13.2230(7)Å,α=104.585(4)°,β=108.268(5)°,γ=111.132(5)°, respectively whileII crystallizes in the orthorhombic system, space groupF2dd, witha=8.7970(4)Å,b=16.1550(8)Å,c=32.170(2)Å. The three-dimensional (3D) framework of these compounds is built up by the linkages of lanthanide atoms and the oxygen atoms of the bischelating oxalate ligands. Instead of four chelating oxalate units surrounding a lanthanide atom (I andII), both lanthanum atoms, inIII, are surrounded by five chelating oxalate groups and that is new. In all the cases within the frame, are observed 8- and 12-membered channels where are localized the guest species, 1,2- or 1,3-diaminopropane cations and free water molecules. The ratio of the guest number (especially the diaminopropane) per 12-membered ring could tune the shape and the size of 12-membered channels: thus, the 12-membered channels, observed forI andII, have elliptical cross-section (5.5Å×11.4Å and 5.2Å×9.5Å) while those, observed forIII, have nearly circular cross-section (9.1Å×9.5Å). The lanthanide atoms are 8, 9 and 10-fold coordinated for Yb (II), Nd (I) and La (III), respectively.View of the 12-membered channel of (C3N2H12)2[La2(C2O4)5]·5H2O.
Keywords: Lanthanide; Oxalate; Template; Open-structure
New process of preparation, X-ray characterisation, structure and vibrational studies of a solid solution LiTiOAs1− xP xO4 (0⩽ x⩽1) by M. Chakir; A. El Jazouli; J.P. Chaminade; F. Bouree; D. de Waal (pp. 18-28).
LiTiOAs1− xP xO4 (0⩽ x⩽1) compounds have been prepared using solutions of Li, Ti, As and P elements as starting products. Selected compositions have been investigated by powder X-ray or neutrons diffraction analysis, Raman and infrared spectroscopy. The structure of LiTiOAs1− xP xO4 ( x=0, 0.5 and 1) samples determined by Rietveld analysis is orthorhombic with Pnma space group. It is formed by a 3D network of TiO6 octahedra and XO4 ( X=As1− xP x) tetrahedra where octahedral cavities are occupied by lithium atoms. TiO6 octahedra are linked together by corners and form infinite chains along a-axis. Ti atoms are displaced from the centre of octahedral units in alternating short (1.700–1.709Å) and long (2.301–2.275Å) Ti–O bonds. Raman and infrared studies confirm the existence of Ti–O–Ti chains. Thermal stability of LiTiOAsO4 has been reported.–Ti–O–Ti– chains and XO4 tetrahedra in LiTiO XO4 ( X=As1− xP x) compounds.
Keywords: Structure; Powder diffraction; X-rays; Neutrons; Raman; Infrared
A facile preparation of nanocrystalline Mo2C from graphite or carbon nanotubes by Zeheng Yang; Peijun Cai; Liang Shi; Yunle Gu; Luyang Chen; Yitai Qian (pp. 29-32).
Nanocrystalline Mo2C powders were successfully synthesized at 500°C by reacting molybdenum chloride (MoCl5) with C (graphite or carbon nanotube) in metallic sodium medium. X-ray powder diffractometer (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscope (XPS) and surface area analyzer (BET method) were used to characterize the samples. Experiments reveal that the carbon source used for the carbide synthesis has a great effect on the particle size and the surface area of the samples. When micro-sized graphite was used as C source the obtained nanocrystalline Mo2C powder consists of particles of 30∼100nm, with a surface area of 2.311m2/g. When carbon nanotubes were used as C source, the as-synthesized Mo2C sample is composed of particles of 20∼50nm, with a surface area of 23.458m2/g, which is an order of magnitude larger than that of the carbide prepared from the graphite.Nanocrystalline Mo2C powders were successfully synthesized at 500°C by reacting MoCl5 with C (graphite or carbon nanotubes) in metallic sodium medium.
Keywords: Molybdenum carbide; Nanoparticle; Chemical synthesis; Transmission electron microscopy; Surface area
Visible light photoelectrochemical activity of K4Nb6O17 intercalated with photoactive complexes by electrostatic self-assembly deposition by Ugur Unal; Yasumichi Matsumoto; Naoko Tamoto; Michio Koinuma; Masato Machida; Kazuyoshi Izawa (pp. 33-40).
Electrostatic self-assembly deposition (ESD) results in the intercalation of Ru(bpy)32+ or methylene blue (MB) into the niobate layered oxide right after the cations come into contact with [Nb6O17]4− nanosheets. Monolayers can be obtained by the exfoliation of proton exchanged K4Nb6O17 (KNbO) in an aqueous tetrabutylammonium (TBA) solution as revealed by the atomic force microscopy micrographs. UV-vis spectra show that intercalated films are able to absorb in the visible light range. Heat-treatment of Ru(bpy)32+ resulted in the red-shift in the absorption spectra, which was assigned to the enhancement in the interaction between the complex molecules and [Nb6O17]4− host layer. Intercalated niobate layered oxides are able to produce photocurrent as a result of the electron transfer from the excited guest molecule to the host layer under visible light illumination. Ru(bpy)32+ intercalated niobate layered oxide shows photocatalytic activity under visible light illumination to produce H2 from water–methanol solution.Charge transfer mechanism in the interlayer of the layered oxide.
Keywords: Layered oxides; Niobate; Exfoliation; Intercalation; Methylene blue; Photochemistry; Water splitting
Effect of ultraviolet irradiation on crystallization behavior and surface microstructure of titania in the sol–gel process by Bifen Gao; Ying Ma; Yaan Cao; Jincai Zhao; Jiannian Yao (pp. 41-48).
Nanosized titania was prepared at various hydrolysis ratios ( r=H2O/Ti) by photo-assisted and conventional sol–gel methods. It was found that hydrolysis ratio and ultraviolet irradiation greatly affect the titania crystallization behavior. The introduction of photo-irradiation benefits anatase formation throughout a wide range of hydrolysis ratio. XPS results show that hydrolysis reaction was promoted by ultraviolet irradiation. In addition, photo-irradiation was also verified to be in favor of the generation of large specific surface area and high crystallinity, which resulted in relative high photocatalytic activity of TiO2 prepared by a photo-assisted sol–gel method.Ultraviolet irradiation was introduced to the sol–gel preparation of titania. Photo-irradiation was verified to have great impact on crystallization behavior and surface microstructure.
Keywords: Titanium dioxide; Sol–gel process; Photo-irradiation; Crystallization; Photocatalysis; Surface microstructure; Anatase; Rutile; Hydrolysis; Condensation
Synthesis, characterisation and anion exchange properties of copper, magnesium, zinc and nickel hydroxy nitrates by Timothy Biswick; William Jones; Pacula Aleksandra Pacuła; Ewa Serwicka (pp. 49-55).
Anion exchange reactions of four structurally related hydroxy salts, Cu2(OH)3NO3, Mg2(OH)3NO3, Ni2(OH)3NO3 and Zn3(OH)4(NO3)2 are compared and trends rationalised in terms of the strength of the covalent bond between the nitrate group and the matrix cation. Powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and elemental analysis are used to characterise the materials. Replacement of the nitrate anions in the zinc and copper salts with benzoate anions is possible although exchange of the zinc salt is accompanied by modification of the layer structure from one where zinc is exclusively six-fold coordinated to a structure where there is both six- and four-fold zinc coordination. Magnesium and nickel hydroxy nitrates, on the other hand, hydrolyse to their respective metal hydroxides.PXRD patterns of exchange products of (a) Zn3(OH)4(NO3)2, (b) Zn5(OH)8(NO3)2·2H2O and (c) Cu2(OH)3NO3 with benzoate anions.
Keywords: Inorganic compounds; X-ray diffraction; Infrared spectroscopy; Thermogravimetric analysis
Selected-control solution-phase route to multiple-dendritic and cuboidal structures of PbSe by Benxia Li; Yi Xie; Yang Xu; Changzheng Wu; Zhengquan Li (pp. 56-61).
Well-crystalline PbSe multiple-dendritic hierarchical structures have been prepared through a facile hydrothermal process in an alkaline glycerol/water solution system using SeO2 as selenium source and hydrous hydrazine as reducing agent at 160°C for 12h. The obtained products were characterized by X-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy, which showed that the obtained products were face-centered cubic PbSe multiple-dendritic superstructures with length of each dendrite ranging from 1.0 to 1.5μm. Additionally, cuboidal PbSe microcrystals with different concave faces can be obtained through a similar process except for using Se powders instead of SeO2 as selenium source and without hydrous hydrazine. The edge lengths of these cuboidal microcrystals range from 1.0 to 2.5μm observed by field emission scanning electron microscopy. The influencing factors for the formation of the two kinds of PbSe microstructures were discussed and the possible growth mechanisms were proposed from the point of crystallographic and kinetic views. The studies on the corresponding photoluminescence (PL) properties of the two kinds of PbSe structures are also carried out.PbSe multiple-dendritic hierarchical structure with 4-fold structural symmetry and cuboidal microcrystals with concave faces were selectively obtained by using different selenium sources in a glycerol/water solution system.
Keywords: Selected-control; Glycerol/water; Dendritic; Cuboidal; PbSe
Visible-light-driven photocatalyst of Bi2WO6 nanoparticles prepared via amorphous complex precursor and photocatalytic properties by Shicheng Zhang; Chuan Zhang; Yi Man; Yongfa Zhu (pp. 62-69).
The visible-light-driven photocatalyst Bi2WO6 nanoparticles have been prepared by calcining amorphous complex precursor at a relatively low temperature of above 450oC. The effects of calcination temperature and time on the structures and properties of Bi2WO6 nanoparticles have been investigated in detail. The photocatalytic activity of the Bi2WO6 powders were evaluated by degradation of RhB molecules in water under visible light irradiation ( λ>400nm). The results showed that the particle size and grain size of Bi2WO6 increased with the calcination temperature and time. The photocatalytic activity of the best sample was about 8.8 times higher than that of the sample prepared by traditional solid state reaction and the photo-degradations was a zero-order reaction. The best route to enhance the photocatalytic activity of Bi2WO6 was to prepare the sample at a lower temperature for a longer time, due to the samples with better crystallization and smaller particle size.Bi2WO6 nanoparticles obtained from amorphous complex precursor under 450°C for 24h.
Keywords: Bi; 2; WO; 6; Photocatalysis; Visible light; Amorphous complex precursor; RhB
Structure and magnetism of 4H-BaMnO3− x (0⩽x⩽0.35) and 4H-Ba0.5Sr0.5MnO3− x (0⩽x⩽0.21) by Josephine J. Adkin; Michael A. Hayward (pp. 70-76).
The synthesis and structure determination of 4H-BaMnO3− x (0⩽x⩽0.35) and 4H-Ba0.5Sr0.5MnO3− x (0⩽x⩽0.21) is described. Neutron powder diffraction data unambiguously show the anion vacancies in the oxygen-deficient phases lie in the hexagonal BaO3− x layers, rather than the cubic layers predicted by previous structural models. The localization of anion vacancies in the hexagonal layers is discussed on the basis of the local co-ordination polyhedra of the metal cations. Low-temperature neutron diffraction data show the oxidized materials adopt antiferromagnetic ordered structures (Ba0.5Sr0.5MnO2.99:TN=265K). Anion-deficient phases do not achieve magnetic order suggesting the Mn(III/IV) charge disorder suppresses long-range magnetic order.Anion vacancy locations in 4H-BaMnO3− x.
Keywords: Neutron diffraction; Hexagonal perovskite; Magnetic order
Heat capacity, enthalpy and entropy of bismuth niobate and bismuth tantalate by M. Hampl; A. Strejc; Sedmidubsky D. Sedmidubský; Ruzicka K. RůžiÄ?ka; Hejtmanek J. Hejtmánek; J. Leitner (pp. 77-80).
The heat capacity and the heat content of bismuth niobate BiNbO4 and bismuth tantalate BiTaO4 were measured by the relaxation method and Calvet-type heat flux calorimetry. The temperature dependencies of the heat capacities in the formC pm=128.628+0.03340 T−1991055/ T2+136273131/ T3 (JK–1mol–1) and 133.594+0.02539 T−2734386/ T2+235597393/ T3 (JK–1mol–1) were derived for BiNbO4 and BiTaO4, respectively, by the least-squares method from the experimental data. Furthermore, the standard molar entropies at 298.15K Sm(BiNbO4)=147.86JK–1mol–1 and Sm(BiTaO4)=149.11JK–1mol–1 were assessed from the low temperature heat capacity measurements. To complete a set of thermodynamic data of these mixed oxides an attempt was made to estimate the values of the heat of formation from the constituent binary oxides.Heat content of bismuth niobate and bismuth tantalate—experimental points determined by the drop method and temperature dependencies obtained by the simultaneous fit of heat capacity and heat content data.
Keywords: BiNbO; 4; BiTaO; 4; Bismuth niobate; Bismuth tantalate; Heat capacity; Heat content; Entropy; Heat of formation
Magnetic structures of the α-Li3Fe2(PO4)3− x(AsO4) x ( x=1, 1.5, 2, 3) solid solution by Goni Aintzane Goñi; J. José Luis Mesa; J. José Luis Pizarro; Fournes Leopold Fournés; Alain Wattiaux; Roger Olazcuaga; M. María Isabel Arriortua; T. Teófilo Rojo (pp. 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 temperatureT N 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.
Keywords: Iron (III) phosphate–arsenate; Crystal structure; Magnetic structure; Mössbauer spectroscopy; Magnetic properties
Synthesis of nickel nanoparticles and carbon encapsulated nickel nanoparticles supported on carbon nanotubes by Jipeng Cheng; Xiaobin Zhang; Ying Ye (pp. 91-95).
Nickel nanoparticles were prepared and uniformly supported on multi-walled carbon nanotubes (MWCNTs) by reduction route with CNTs as a reducing agent at 600°C. As-prepared nickel nanoparticles were single crystalline with a face-center-cubic phase and a size distribution ranging from 10 to 50nm, and they were characterized by transmission electron microscopy (TEM), high-resolution TEM and X-ray diffraction (XRD). These nickel nanoparticles would be coated with graphene layers, when they were exposed to acetylene at 600°C. The coercivity values of nickel nanoparticles were superior to that of bulk nickel at room temperature.TEM image of nickel nanoparticles supported on carbon nanotubes.
Keywords: Carbon nanotube; Nickel nanoparticles; Microstructure; Carbon encapsulation; Magnetic property
Sacrificial template growth of CdS nanotubes from Cd(OH)2 nanowires by Xuemei Li; Haibin Chu; Yan Li (pp. 96-102).
A diffusion-controlled process was proposed for the preparation of inorganic nanotubes from nanowires. The preformed Cd(OH)2 nanowires were used as the sacrificial templates to generate CdS nanotubes with different wall thickness. The axle–sleeve transition state found in-between the precursor and the formation of products proves the diffusion-controlled mechanism. CdS nanotubes can be prepared via this method at different temperature and with various sulfide sources. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) results showed that all obtained CdS nanotubes consist conglomerated crystallites, and the crystallinity can be altered by changing the temperature of the growth process. The wall thickness of the produced CdS nanotubes can be controlled by changing the concentration of the sulfide source and stopping the reaction at different stages.CdS nanotubes were prepared with Cd(OH)2 nanowires as the sacrificial templates. Diffusion played an important role in the process. The morphology of the produced nanotubes can be varied by alternating the reaction conditions.
Keywords: Nanostructures; Nanotubes; Nanowires; Template approach; CdS; Cd(OH); 2
Crystal structure and vibrational properies of Rb2MgWO2(PO4)2—A new framework phosphate by Maczka M. Mączka; Waskowska A. Waśkowska; J. Hanuza (pp. 103-110).
The new compound Rb2MgWO2(PO4)2 has been synthesized and characterized by a single-crystal X-structure determination, and IR and Raman spectroscopic studies. The crystal structure is orthorhombic, space group Pbca, with the unit cell dimensionsa=9.891(2),b=12.641(2),c=15.338(3)Å,Z=8. Compared to the K2 MIIWO2(PO4)2 series, where MII=Mg, Mn, Fe, Co, Ni, and Cd, the volume of the unit cell in the present compound is nearly doubled. The MgO6 and WO6 octahedra are arranged into polyhedral groups consisting of two edge sharing MgO6 joined by corners with two WO6 octahedra. These groups are interconnected through the PO4 tetrahedra into layers in a× b plane. The Rb+ ions perform thermally activated displacements within the cavities formed between the polyhedral layers. The origin of various Raman and IR modes is discussed. These results indicate that a clear energy gap exists between the stretching and remaining modes. The most intense modes are shown to be due to vibrations of the W–O bonds.Projection of the Rb2MgWO2(PO4)2 crystal structure along the b-axis.
Keywords: Rb; 2; MgWO; 2; (PO; 4; ); 2; Phosphate; Crystal structure; Phonon properties
Electron-doping through LaIII-for-SrII substitution in (Sr1− xLa x)2FeTaO6: Effects on the valences and ordering of the B-site cations, Fe and Ta by E.-L. Rautama; T.S. Chan; R.S. Liu; J.M. Chen; H. Yamauchi; M. Karppinen (pp. 111-116).
We have employed aliovalent A-site cation substitution, LaIII-for-SrII, to dope the Sr(Fe0.5Ta0.5)O3 perovskite oxide with electrons. Essentially single-phase samples of (Sr1− xLa x)(Fe0.5Ta0.5)O3 were successfully synthesized up to x≈0.3 in a vacuum furnace at 1400°C. The samples were found to crystallize (rather than with orthorhombic symmetry) in monoclinic space group P21/ n that accounts for the partial ordering of the B-site cations, Fe and Ta. With increasing La-substitution level, x, the degree of Fe/Ta order was found to increase such that the La-richest compositions are best described by the B-site ordered double-perovskite formula, (Sr,La)2FeTaO6. From Fe L3 and Ta L3 XANES spectra it was revealed that upon electron doping the two B-site cations, FeIII and TaV, are both prone to reduction. Magnetic susceptibility measurements showed spin-glass type behaviour for all the samples with a transition temperature slightly increasing with increasing x.Valence states of Fe and Ta are controlled in the partially ordered perovskite oxide, (Sr,La)2FeTaO6, through aliovalent LaIII-for-SrII substitution.
Keywords: Double perovskite; Cation ordering; Valence states; XANES spectroscopy
Dynamics of superionic Rb3H(SeO4)2 single crystals studied by1H and87Rb spin–lattice relaxation by Ae Ran Lim; M. Ichikawa (pp. 117-121).
The1H and87Rb spin–lattice relaxation and spin–spin relaxation times in superionic Rb3H(SeO4)2 single crystals grown by the slow evaporation method were measured over the temperature range 160–450K. The temperature dependencies of the1H T1, T1 Ï?, and T2 are measured. In the ferroelastic phase, T1 differs from T1 Ï?, which is in turn different from T2, although these three relaxation times converge to similar values near 410K. This transition seems to occur at temperature which is about 40K lower than the superionic transition temperature. The observation of liquid-like values of the1H T1, T1 Ï?, and T2 in the high temperature is compatible with the phase being superionic, indicating that the destruction and reconstruction of hydrogen bonds does indeed occur at high temperature. In addition, the87Rb T1 and T2 values at high temperature were similar (on the order of milliseconds), a trend that was also observed for1H T1 and T2. This behavior is expected for most hopping-type ionic conductors, and could be attributed to interactions between the mobile ions and the neighboring group ions within the crystal. The motion giving rise to this liquid-like behavior is related to the superionic motion.
Keywords: PACS; B: 81.10.−h; D: 77.80 Bh; E: 76.60 kPhysics of crystal growth; Phase transition; Nuclear magnetic resonance and relaxation
Hydrothermal synthesis and characterization of two new bicapped Keggin heteropoly tungstovanadated derivatives by Y.-B. Ya-Bing Liu; L.-M. Li-Mei Duan; X.-M. Xiao-Mei Yang; J.-Q. Ji-Qing Xu; Q.-B. Qing-Bin Zhang; Y.-K. Yu-Kun Lu; Jian Liu (pp. 122-129).
Two new heteropoly tungstovanadate derivatives, [Fe(phen)3]2[W10.5V4.5O42]·3H2O (1) and [Fe(phen)3]2[W10V5O42].6H2O (2) (phen=1,10′-phenanthroline), have been synthesized under hydrothermal conditions by using different starting materials, and characterized by elemental analysis, IR, ESR, XPS, TGA and single-crystal X-ray diffraction analysis. Crystal data for compound 1: C72H54Fe2N12O45V4.5W10.5, monoclinic, space group C2/c,a=30.244(9)Å,b=13.586(3)Å,c=24.707Å,β=99.882(8)°,V=10002(5) Å3,Z=4; for compound 2, C72H60Fe2N12O48V5W10, monoclinic, space group C2/c,a=30.246(6) Å,b=13.909(3)Å,c=25.329(5) Å,β=100.34(3)°,V=10483(4) Å3,Z=4. The crystal structure analysis reveals that both polyoxoanions are decorated with the [Fe(phen)3]2+ cations, and that they have analogous structure to each other with slightly different packing modes of the polyoxoanions, [Fe(phen)3]2+ cations and water molecules. They are further linked to form two-dimensional (2D) supramolecular networks through extensive hydrogen bonding.Two new heteropoly tungstovanadate derivatives, [Fe(phen)3]2[W10.5V4.5O42]·3H2O(1) and [Fe(phen)3]2[W10V5O42]·6H2O(2) (phen=1,10′-phenanthroline), have been synthesis under hydrothermal conditions by using different starting materials. Compound1 is the first example of discrete bicapped Keggin heteropoly tungstovanadates. Polyoxoanions, [Fe(phen)3]2+ cations and water molecules act as building blocks to form two-dimensional (2-D) supramolecular layers through extensive hydrogen bonding.
Keywords: Bicapped Keggin structure; Hydrothermal synthesis; Polyoxometalates; Property characterization
Synthesis and structure of the ternary and quaternary strontium nitride halides, Sr2N( X, X′) ( X, X′=Cl, Br, I) by Amy Bowman; Ronald I. Smith; Duncan H. Gregory (pp. 130-139).
A number of new, layered nitride mixed halides have been synthesised in the quaternary phase systems Sr–N–Cl–Br and Sr–N–Br–I. The variation in structure with composition has been investigated by powder X-ray and powder neutron diffraction techniques and the structure of strontium nitride iodide, Sr2NI, has been determined for the first time (rhombohedral space group R-3 m,a=4.0103(1)Å,c=23.1138(2)Å,Z=3). A continuous solid solution exists between Sr2NCl and Sr2NBr with intermediate compounds adopting the same anti-α-NaFeO2 structure (rhombohedral space group R-3 m) as the ternary end members. A similar smooth and linear relationship between structure and composition is seen from Sr2NBr to Sr2NI and hence cubic close packing of metal–nitrogen layers is adopted regardless of halide, X ( X′). While nitride and halide anions occupy distinct crystallographic sites, there is no ordering of the halides in the quaternary materials irrespective of stoichiometry or temperature (between 3 and 673K).New ternary and quaternary nitride halides, Sr2N(Cl, Br) and Sr2N(Br, I) have been synthesised. The CCP layered structures of the insulating nitride halides persist irrespective of the halide, X, or the temperatures investigated.
Keywords: Synthesis; Powder X-ray diffraction; Powder neutron diffraction; Structure; Nitrides; Halides; Strontium
Ferromagnetic-phase transition in the spinel-type CuCr2Te4 by Takeshi Suzuyama; Junji Awaka; Hiroki Yamamoto; Shuji Ebisu; Masakazu Ito; Takashi Suzuki; Takao Nakama; Katsuma Yagasaki; Shoichi Nagata (pp. 140-144).
Ferromagnetic-phase transition in spinel-type CuCr2Te4 has been clearly observed. CuCr2Te4 is a telluride–spinel with the lattice constanta=11.134Å, which has been synthesized successfully. The heat capacity exhibits a sharp peak due to the ferromagnetic-phase transition with the Curie temperatureTC=326K. This value of TC corresponds exactly to that of the negative peak of d M/d T in low field of 1.0Oe. The magnetic susceptibility shows the Curie–Weiss behavior between 380 and 650K with the effective magnetic momentμeff=4.14μB/Cr-ion and the Weiss constantθ=+357K. The low temperature magnetization indicates the spin-wave excitations, where the existence of first term of Bloch T3/2 law and the next T5/2 term are verified experimentally. This spin-wave excitation is detected up to approximately 250K which is a fairly high temperature.Molar heat capacity of CuCr2Te4 over a wide temperature range of 2.17–373K.
Keywords: Spinel-type CuCr; 2; Te; 4; Telluride–spinel; Ferromagnetism; Heat capacity; Magnetization; Magnetic susceptibility; Spin-wave excitation
Inorganic–organic hybrid compounds: Synthesis and characterization of three new metal phosphonates with similar characteristic structural features by Sebastian Bauer; Thomas Bein; Norbert Stock (pp. 145-155).
The phosphonocarboxylic acid H(HO3PCH2)2NH-CH2C6H4-COOH (H5 L) was synthesized and characterized by NMR- and IR-spectroscopy, thermogravimetric (TG) analysis and single-crystal X-ray diffraction. Reactions ofH5 L with samarium(III) chloride and calcium(II) chloride resulted in three new compounds, Sm[(O3PCH2)2NH-CH2C6H4-COOH]·H2O (1), Ca[H(O3PCH2)2NH-CH2C6H4-COOH]·H2O (2), and Ca[(HO3PCH2)2NH-CH2C6H4-COOH]2·4H2O (3). The single-crystal structure determination of the title compounds reveals that inH5 L as well as in compounds1,2, and3 zwitterions are present. Within the M–O building units of the metal phosphonates we observed a different degree of dimensionality, depending on the oxidation state of the metal ion and the synthesis conditions. In1, one-dimensional chains of edge-sharing SmO8 polyhedra are observed while in2, isolated units of edge-sharing CaO6 octahedra and in3 isolated CaO6 octahedra are observed. However, looking at the organic part, the rigid phenyl carboxylic acid moieties arrange in a “zipper-like� fashion and hydrogen bonding plays an important role in the stabilization of the crystal structure. The title compounds were further characterized by IR spectroscopy and TG analysis. Additionally, the thermal stability of1 was investigated by temperature-dependent X-ray diffraction.Hydrothermal reactions of the phosphonocarboxylic acid H(HO3PCH2)2NH-CH2C6H4-COOH with Sm3+ and Ca2+ salts has led to three new inorganic–organic hybrid compounds. All crystal structures contain phosphonate zwitterions and have a layer-like arrangement. The rigid organic groups arrange in a “zipper-like� fashion and hydrogen bonding plays an important role in the stabilization of the crystal structures.
Keywords: Metal phosphonates; Phosphonocarboxylic acid; Inorganic–organic hybrid compounds; Crystal structure; Samarium; Calcium
Hydrothermal synthesis and characterization of a new three-dimensional hybrid zinc phosphate [Zn2(HPO4)2(4,4′-bipy)]·3H2O with neutral porous framework by Lei Wang; Ming Yang; Guanghua Li; Zhan Shi; Shouhua Feng (pp. 156-160).
Employing 4,4′-bipyridine as a bridged ligand, a new three-dimensional (3-D) hybrid zinc phosphate [Zn2(HPO4)2(4,4′-bipy)]·3H2O has been prepared under hydrothermal conditions and characterized by single crystal X-ray diffraction. This compound crystallizes in the monoclinic space group C2/ c, with cell parameters,a=21.188(4)Å,b=10.229(2)Å,c=9.0656(18)Å,β=90.21(3)°,V=1964.8(7)Å3 andZ=4. The connectivity of the ZnO3N and HPO4 tetrahedra results in a 2-D neutral layer that with interesting 4,82 net along the bc plane. Furthermore, the 4,4′-bipyridine molecule links the 4,82 net into a 3-D structure. The water molecules sit in the middle of the channels and interact with the framework via hydrogen bonds. The compound exhibits intense photoluminescence at room temperature.View of the two-dimensional neutral zinc phosphate layer along the bc plane.
Keywords: Hybrid compound; Neutral framework; Hydrothermal synthesis; Zinc phosphate; Crystal structure
Magnetic and vibrational properties and crystal structure of Sr9.2Co1.3(PO4)7 with disordered arrangements of some strontium, cobalt, and phosphate ions by Alexei A. Belik; Artem P. Malakho; Petro S. Salamakha; Bogdan I. Lazoryak (pp. 161-168).
Solid solutions of Sr9+ xCo1.5− x(PO4)7 were found in the compositional range of0.05⩽x⩽0.30. The structure of Sr9.2Co1.3(PO4)7 (x=0.2) was determined from single crystal X-ray diffraction (space groupR3¯m (No. 166);Z=3;a=10.6100(5)Ã… andc=19.6960(5)Ã…;V=1920.17(14)Ã…3;Ï?cal=4.014gcm-3;μ=20.377mm-1) and refined toR1=0.0343 andwR2=0.0633 for 586 reflections withI>2σ(I). Sr9.2Co1.3(PO4)7 is structurally related to β-Ca3(PO4)2 and Sr3(PO4)2 and has disordered arrangements of some Sr2+, Co2+, and PO43− ions. Sr2+ ions at a 9 e site are statistically disordered among four positions near the center of symmetry. Co2+ and Sr2+ ions are split along the c-axis to occupy a 6 c site that is 75% vacant. The P1O4 tetrahedra are orientationally disordered. Sr2+ ions at an 8-fold coordinated 18 h site, Co2+ ions at an octahedral 3 a site, and the P2O4 tetrahedra are ordered in the structure of Sr9.2Co1.3(PO4)7. Features of Raman spectra are discussed in relation to the crystallographic structure of Sr9.2Co1.3(PO4)7 and in comparison with Raman spectra of β-Ca3(PO4)2-type and Sr3(PO4)2-type compounds. Sr9.2Co1.3(PO4)7 is paramagnetic between 2 and 300K with an effective magnetic moment of 4.98 μB per Co2+ ion.Disordered structural elements in Sr9.2Co1.3(PO4)7: the P1O4 tetrahedron and the Sr31, Sr32, Sr4, and Co4 sites. The Co4−O21 bonds and ordered P2O4 and Co5O6 polyhedra are also shown.
Keywords: Strontium phosphate; Cobalt phosphate; Crystal structure; Single crystal; Raman spectroscopy; Magnetic susceptibility
High-pressure synthesis and crystal structure analysis of NaMn2O4 with the calcium ferrite-type structure by Junji Akimoto; Junji Awaka; Norihito Kijima; Yasuhiko Takahashi; Yuichi Maruta; Kazuyasu Tokiwa; Tsuneo Watanabe (pp. 169-174).
Single crystals of a new sodium manganese oxide, NaMn2O4, were synthesized for the first time using a high-temperature and high-pressure technique. The NaMn2O4 single crystal is black, has a needle shape, and crystallizes in the orthorhombic calcium ferrite-type structure, space group Pnam witha=8.9055(18)Å,b=11.0825(22)Å,c=2.8524(5)Å,V=281.52(9)Å3, andZ=4. The structure was determined from a single-crystal X-ray study and refined to the conventional valuesR=0.041 andwR=0.034 for 1190 observed reflections. The framework structure is built up from edge-sharing chains of MnO6 octahedra that condense to form one-dimensional tunnels in which the sodium atoms are located. The Mn–O bond distance and bond valence analyses revealed the manganese valence Mn3+/Mn4+ ordering in the two “double rutile� chains of NaMn2O4.Crystal structure of NaMn2O4 viewed along [001]. The manganese valence Mn3+/Mn4+ ordering has been observed in the two “double rutile� chains in NaMn2O4.
Keywords: NaMn; 2; O; 4; Sodium manganese oxide; Calcium ferrite; High-pressure synthesis; Single-crystal X-ray diffraction; Structure analysis; Charge ordering
Syntheses and crystal structures of a series of new divalent metal phosphonates with imino-bis(methylphosphonic acid) by B.-P. Bing-Ping Yang; Andrey V. Prosvirin; H.-H. Han-Hua Zhao; J.-G. Jiang-Gao Mao (pp. 175-185).
Hydrothermal reactions of divalent transition metal salts with imino-bis(methylphosphonic acid), NH(CH2PO3H2)2 (H4L) afforded three new metal phosphonates, namely, Cu[NH(CH2PO3H)2]1, {Co[NH2(CH2PO3H)(CH2PO3)](H2O)2}·H2O2 and Mn[NH2(CH2PO3H)(CH2PO3)](H2O)3. When HO2C(CH2)3N(CH2PO3H2)2 was used as the phosphonate ligand and 4,4′-bipy as the second metal linker, {Cu4[NH(CH2PO3)2]2(4,4′-bipy)(H2O)4}·9H2O4 with a pillared layered architecture was obtained. The NH(CH2PO3)2 anion resulted from the cleavage of the HO2C(CH2)3-group during the reaction. Although compounds1–3 have a same M/L ratio (1:1), they exhibit totally different structures.Compound1 has a linear chain structure, in which each pair of square-pyramidal coordinated copper(II) ions are bridged by two phosphonate oxygen atoms to form a Cu2O2 dimeric unit, and such dimeric units are further interconnected via phosphonate groups to form a [010] chain. Compound2 has a layered architecture built from CoO6 octahedra bridged by phosphonate ligands. In compound3, the interconnection of the manganese(II) ions by bridging imino-diphosphonate ligands leads to a 3D network. Compound4 has a pillar-layered structure, the layers composed of Cu(II) ions bridged by aminodiphosphonate ligands are interconnected by 4,4′-bipy ligands to form channels along c-axis. Several factors that affect the structures of the metal phosphonates formed have also been discussed. Compounds2 and3 show predominant antiferromagnetic interactions between magnetic centers.Four new metal phosphonates, namely, Cu[NH(CH2PO3H)2]1, {Co[NH2(CH2PO3H)(CH2PO3)](H2O)2}·H2O2, Mn[NH2(CH2PO3H)(CH2PO3)](H2O)3 and {Cu4[NH(CH2PO3)2]2(4,4′-bipy)(H2O)4}·9H2O4 have been synthesized and structurally characterized. Compound1 has a linear chain structure, and compound2 is layered. Compound3 is three dimensional whereas compound4 has a pillar-layered structure. Compounds2 and3 show predominant antiferromagnetic interactions between magnetic centers.
Keywords: Hydrothermal syntheses; Crystal structures; Metal diphosphonates; Inorganic–organic hybrids; Magnetic properties
Crystal structures of alkali-metal indium (III) phosphates of [ M3In(PO4)2] n ( M=K,n=10; M=Rb,n=2) compounds, and band structures and chemical bond properties of [Rb3In(PO4)2]2 crystal by Yongchun Zhang; Wendan Cheng; Dongsheng Wu; Hao Zhang; Dagui Chen; Yajing Gong; Zigui Kan; Jing Zhu (pp. 186-194).
Ternary indium (III) phosphates with three-dimensional frameworks, [ M3In(PO4)2] n ( M=K,n=10; M=Rb,n=2), are found and firstly reported in this paper. These compounds have been obtained by high temperature solid-state reactions and their crystal structures have been determined by single crystal X-ray diffraction analysis. The title compounds, which crystallize in monoclinic system, possess the same [In(PO4)2] n3 n− anionic frameworks built up from interconnected InO6 octahedra and PO4 tetrahedra and have an interesting tunnel structure where M+ cations are located. Optical and bonding properties of [Rb3In(PO4)2]2 are investigated in terms of measured absorption and emission spectra, and calculated band structures and density of states. The crystal band structures obtained by the DFT method show that the solid compound of [Rb3In(PO4)2]2 is an insulator with direct band gap, and the P–O covalent bond characters are larger than the In–O ones in this compound.
Keywords: Phosphate; Crystal structure; Band structure; DFT method
Structure and magnetism of NaRu2O4 and Na2.7Ru4O9 by K.A. Regan; Q. Huang; M. Lee; A.P. Ramirez; R.J. Cava (pp. 195-204).
The structures of NaRu2O4 and Na2.7Ru4O9 are refined using neutron diffraction. NaRu2O4 is a stoichiometric compound consisting of double chains of edge sharing RuO6 octahedra. Na2.7Ru4O9 is a non-stoichiometric compound with partial occupancy of the Na sublattice. The structure is a mixture of single, double and triple chains of edge-shared RuO6 octahedra. NaRu2O4 displays temperature independent paramagnetism withχ0=1.23×10-4emu/molRuOe. Na2.7Ru4O9 is paramagnetic,χ0=2.0×10-4emu/molOe withΘw=-11.8K and a Curie constant of 0.0119emu/molOeK. Specific heat measurements reveal a small upturn at low temperatures, similar to the upturn observed in La4Ru6O19. The electronic contribution to the specific heat ( γ) for Na2.7Ru4O9 was determined to be15mJ/moleRuK2.Magnetic susceptibility versus temperature data for NaRu2O4 (closed squares) and Na2.7Ru4O9 (open triangles).χ0=1.2×10-4emu/molRuOe for NaRu2O4,χ0=2.0×10-4emu/molRuOe for Na2.7Ru4O9. Inset: Inverse magnetic susceptibility vs. temperature data for Na2.7Ru4O9. A linear fit of the high temperature data from 125 to 200K shows Curie–Weiss behavior, givingΘcw=-11.8K andC=0.0119emu/molOeK.
Keywords: Ruthenate; Bronze; NaRu; 2; O; 4; Na; 2.7; Ru; 4; O; 9; Ferrite; Paramagnetic
The actual structure of K6(VO)2(V2O3)2(PO4)4(P2O7): Ordered distribution of P2O7 groups and charge ordering of vanadium by A. Leclaire; B. Raveau (pp. 205-211).
The actual structure of the vanadium phosphate K6(VO)2(V2O3)2(PO4)4(P2O7) has been determined, using a much larger single crystal than previously used for the isostructural Rb-phase. The actual supercell is four times larger than the corresponding orthorhombic subcell witha=26.777Å,b=28.480Å,c=6.972Å,α=β=γ=90°. The structure resolution, performed in the triclinic space group C-1, shows that the P2O7 groups alone are responsible for the superstructure, all the other atoms keeping the atomic positions of the orthorhombic subcell. This structural study shows a perfect ordering of the P2O7 groups in the actual structure, in contrast to the results obtained from the subcell. Concomitantly, the V4+ and V5+ are found to be ordered in the form of [110] stripes.Partial projection showing the ordering of the P2O7 units (in dark gray) and the ordering of the V5+ (light gray) and of the V4+ (medium gray) species.
Keywords: Potassium vanadium phosphates; Monophosphates mixed to diphosphates; Actual structure; Mixed V; 4+; /V; 5+; vanadium phosphate; Charge ordering of vanadium; Ordered frameworks
Effect of La filling on thermoelectric properties of La xCo3.6Ni0.4Sb12-filled skutterudite prepared by MA–HP method by Junyou Yang; Yuehua Chen; Wen Zhu; Jiangying Peng; Siqian Bao; Xi’an Fan; Xingkai Duan (pp. 212-216).
Starting from elemental powder mixtures, single-phase La xCo3.6Ni0.4Sb12(x=0, 0.1, 0.4, 0.6)-filled skutterudites were synthesized via the route of mechanical alloying–hot pressing (MA–HP) in this paper. With increasing of La fraction, the lattice spacing of filled skutterudite phase increases and its variation follows the Vegard's law. The magnitude of the Seebeck coefficient and electrical resistivity show slight increases with increasing of La filling fraction; thermal conductivity of the filled skutterudite decreases and the resultant figure of merit increases with increase of La filling fraction. The as-HPed filled skutterudite has a composite nanocrystalline microstructure, which includes some coral-like clusters with relatively large spoke-like grains about 300nm in length and a superfine equiaxial nanocrystalline matrix with an average grain size of about 50nm. The coral-like cluster corresponds to the prime filled skutterudite formed directly by MA, while the filled skutterudite formed during hot pressing, which has the same nucleation condition and experiences less grain growth, develops equiaxially into the superfine nanocrystalline matrix.Thermal conductivity of the filled skutterudite versus temperature and La filling content.
Keywords: Thermoelectric properties; Filled skutterudite; Nanocrystalline; Mechanical alloying
Synthesis and properties of pyrazine-pillared Ag3Mo2O4F7 and AgReO4 layered phases by Haisheng Lin; Bangbo Yan; Paul D. Boyle; Paul A. Maggard (pp. 217-225).
The new pyrazine-pillared solids, AgReO4(C4H4N2) (I) and Ag3Mo2O4F7(C4H4N2)3 (C4H4N2=pyrazine, pyz) (II), were synthesized by hydrothermal methods at 150°C and characterized using single crystal X-ray diffraction (I— P21 /c, No. 14, Z=4, a=7.2238(6)Å, b=7.4940(7)Å, c=15.451(1)Å, β=92.296(4)°;II— P2 /n, No. 13, Z=2, a=7.6465(9)Å, b=7.1888(5)Å, c=19.142(2)Å, β=100.284(8)°), thermogravimetric analysis, UV-Vis diffuse reflectance, and photoluminescence measurements. Individual Ag(pyz) chains inI are bonded to three perrhenate ReO4– tetrahedra per layer, while each layer inII contains sets of three edge-shared Ag(pyz) chains ( π– π stacked) that are edge-shared to four Mo2O4F73– dimers. A relatively small interlayer spacing results from the short length of the pyrazine pillars, and which can be removed at just slightly above their preparation temperature, at >150–175°C, to produce crystalline AgReO4 forI, and Ag2MoO4 and an unidentified product forII. Both pillared solids exhibit strong orange-yellow photoemission, at 575nm forI and 560nm forII, arising from electronic excitations across (charge transfer) band gaps of 2.91 and 2.76eV in each, respectively. Their structures and properties are analyzed with respect to parent ‘organic free’ silver perrhenate and molybdate solids which manifest similar photoemissions, as well as to the calculated electronic band structures.Two new pyrazine-pillared hybrid solids have been synthesized under hydrothermal conditions, Ag3Mo2O4F7(pyz)3 (shown) and AgReO4(pyz). These solids are novel examples of layered structures containing pillaring Ag(pyz) chains and also the unique Mo2O4F73– dimer in the former. Both exhibit orange-yellow photoluminescence, and the pyrazine pillars can be removed at slightly above the synthesis temperatures to give corresponding crystalline metal-oxide phases.
Keywords: Pillared; Layered; Perrhenate; Molybdate; Optical properties; Pyrazine; Extended Hückel calculations
Preparation of monodispersed microporous SiO2 microspheres with high specific surface area using dodecylamine as a hydrolysis catalyst by Jiaguo Yu; Li Zhao; Bei Cheng (pp. 226-232).
A novel and simple method for the synthesis of monodispersed microporous SiO2 microspheres with high specific surface area was developed by hydrolysis of tetraethoxysilane (TEOS) in a water–ethanol mixed solution and using dodecylamine (DDA) as hydrolysis catalyst and template. The as-prepared products were characterized with differential thermal analysis–thermogravimetry, scanning electron microscopy, high-resolution transmission electron microscopy, small angle X-ray diffraction and nitrogen adsorption. The effects of experimental conditions including hydrolysis temperatures, calcination temperature and concentrations of TEOS and DDA on the morphology and pore parameters of the as-prepared SiO2 microspheres were investigated and discussed. The results showed that hydrolysis temperature and concentrations of TEOS and DDA are important parameters for the control of size and morphology of particles. The specific surface area and specific pore volume of the as-prepared SiO2 microspheres increased with increasing DDA concentration and calcination temperature. DDA may act not only as a good hydrolysis catalyst but also as a template for the formation of monodispersed SiO2 microspheres with high specific surface area. This research may provide new insight into the synthesis of monodispersed microporous SiO2 microspheres.Monodispersed microporous SiO2 microspheres with high specific surface area were prepared by hydrolysis of tetraethoxysilane (TEOS) using dodecylamine (DDA) as hydrolysis catalyst and the effects of experimental conditions on the morphology and pore parameters of the as-prepared SiO2 microspheres were investigated and discussed.
Keywords: SiO; 2; microspheres; Microporous; Monodispersed; TEOS; Dodecylamine
Zirconium titanate ceramic pigments: Crystal structure, optical spectroscopy and technological properties by M. Dondi; F. Matteucci; G. Cruciani (pp. 233-246).
Srilankite-type zirconium titanate, a promising structure for ceramic pigments, was synthesized at 1400°C following three main doping strategies: (a) ZrTi1−xA xO4, (b) ZrTi1− x−yAxB yO4 and (c) Zr1−xC xTiO4 where A=Co, Cr, Fe, Mn, Ni or V (chromophores), B=Sb or W (counterions) and C=Pr (chromophore);x=y=0.05. Powders were characterized by XRD with Rietveld refinements and DRS in the UV–visible–NIR range; technological properties were appraised in several ceramic matrices (frits, glazes and body). Zirconium titanate can be usefully coloured with first row transition elements, giving green and greenish yellow (Co and Ni); orange-buff (Cr and V); tan-brown hues (Mn and Fe). In industrial-like synthesis conditions, a disordered structure as (Zr,Ti)O2, with both Zr and Ti randomly distributed in the octahedral site, is achieved. Doping with chromophores and counterions induces unit cell dimensions variation and causes an oversaturation in zirconium oxide. Optical spectroscopy reveals the occurrence of Co2+, Cr3+, Fe3+, Mn2+, Mn3+, Ni2+, V3+ and V4+. The zirconium titanate pigments fulfil current technological requirements for low-temperature applications, but exhibit a limited chemico-physical stability for higher firing temperature and in chemically aggressive media.Picture of ZrTiO4 structure.
Keywords: Ceramic pigments; Crystal structure; Order–disorder; Optical spectroscopy; Zirconium titanate; Srilankite
Synthesis and characteristics of a novel 3-D organic amine oxalate: (enH2)1.5[Bi3(C2O4)6(CO2CONHCH2CH2NH3)]·6.5H2O by Xiaohong Yu; Hanhui Zhang; Yanning Cao; Yiping Chen; Zhen Wang (pp. 247-252).
A novel 3-D compound of (enH2)1.5[Bi3(C2O4)6(CO2CONHCH2CH2NH3)]·6.5H2O has been hydrothermally synthesized and characterized by IR, ultraviolet–visible diffuse reflection integral spectrum (UV–Vis DRIS), fluorescence spectra, TGA and single crystal X-ray diffraction. It crystallizes in the monoclinic system, space group C2/ c witha=31.110(8)Å,b=11.544(3)Å,c=22.583(6)Å,β=112.419(3)°,V=7497(3)Å3,Z=8,R1=0.0463 andwR2=0.1393 for unique 7686 reflectionsI>2σ(I). In the title compound, the Bi atoms have eight-fold and nine-fold coordination with respect to the oxygen atoms, with the Bi atoms in distorted dodecahedron and monocapped square antiprism, respectively. The 3-D framework of the title compound contains channels and is composed of linkages between Bi atoms and oxalate units, forming honeycomb-like layers with two kinds of 6+6 membered aperture, and pillared by oxalate ligands and monamide groups. The channels have N-ethylamine oxalate monamide group−CO2CONHCH2CH2NH3+, which is formed by the in situ reaction of en and oxalate acid. At room temperature, the complex exhibits intense blue luminescence with an emission peak at 445nm.A novel 3-D organic amine oxalate has been synthesized by hydrothermal method. In this compound, the Bi atoms and oxalate units form honeycomb-like layers with two kinds of 6+6 membered aperture. The layers are pillared by oxalate ligands and monamide groups to construct a 3-D framework. At room temperature, the complex exhibits intense blue luminescence with an emission peak at 445nm.
Keywords: Hydrothermal synthesis; Crystal structure; Oxalate; Luminescence
Influence of metal ions on the structures of Keggin polyoxometalate-based solids: Hydrothermal syntheses, crystal structures and magnetic properties by Zhenyu Shi; Jun Peng; Gomez-Garcia Carlos J. Gómez-García; Samia Benmansour; Xiaojun Gu (pp. 253-265).
Three new Keggin polyoxometalate (POM)-based compounds linked to 3d metal complexes have been synthesized under hydrothermal conditions: [Cu(phen)2]2{[Cu(phen)]2 [SiMo12O40(VO)2]} (1), {[Zn(phen)2]2[GeMo12O40(VO)2]}{[Zn(phen)2(H2O)]2 [GeMo12O40(VO)2]}·3H2O (2) and {[Co(phen)2]2[PMo12O40(VO)2]}{[Co(phen)2(OH)]2 [PMo12O40(VO)2]}·2.5H2O (3) (phen=1,10-phenanthroline). These three compounds present, as building blocks, the bicapped Keggin anions [ XMo12O40(VO)2] ( X=Si, Ge and P). Compound1 consists of a bicapped Keggin anion [SiMo12O40(VO)2]2− linked to two [Cu(phen)]+ complexes with two [Cu(phen)2]+ countercations. Compound2 contains two bicapped Keggin anions [GeMo12O40(VO)2]4−, one linked to two [Zn(phen)2(H2O)]2+ cations and the other one linked to two [Zn(phen)2]2+ cations. Compound3 is a two-dimensional POM-based square network formed by bicapped Keggin anions [PMo12O40(VO)2]4− connected by [Co(phen)2]2+ cations. Discrete bicapped Keggin anions [PMo12O40(VO)2] linked to two [Co(phen)2(OH)]+ cations are located between the layers. The magnetic properties show the presence of antiferromagnetic interactions among the reduced Mo(V) atoms (in the three compounds) plus a paramagnetic contribution from the V(IV) atoms (in1 and2). Compound3 shows, in addition, an antiferromagnetic interaction between the Co(II) and the V(IV) ions directly linked through an oxygen bridge. The low-temperature ESR spectra of compound3 confirm the presence of the reduced Mo(V) ions and the antiferromagnetic coupling between the Co(II) and the V(IV) ions.Three new Keggin polyoxometalate-based compounds have been synthesized under hydrothermal condition. These three compounds present the bicapped Keggin anions [ XMo12O40(VO)2] ( X=Si, Ge and P) as building blocks. Among the three compounds, compound3 is a two-dimensional polyoxometalate-based square network formed by bicapped Keggin anions [PMo12O40(VO)2]4− connected by [Co(phen)2]2+ cations. Discrete bicapped Keggin anions [PMo12O40(VO)2] linked to two [Co(phen)2(OH)]+ cations are located between the layers.
Keywords: Hydrothermal synthesis; Bicapped Keggin; Magnetic polyoxometalates
White-light-emitting long-lasting phosphorescence in Dy3+-doped SrSiO3 by Jinyong Kuang; Yingliang Liu; Jianxian Zhang (pp. 266-269).
We report on a luminescent phenomenon in Dy3+-doped SrSiO3 long-lasting phosphor. After irradiation by a 254-nm UV lamp for 5min, the Dy3+-doped SrSiO3 phosphor emits white light-emitting long-lasting phosphorescence for more than 1h even after the irradiation source has been removed. Photoluminescence, long-lasting phosphorescence and thermoluminescence (TL) spectra are used to explain this phenomenon. Photoluminescence spectra reveal that the white light-emitting long-lasting phosphorescence originated from the two mixtures of Dy3+ characteristic luminescence, the 480-nm blue emission (4 F9/2→6 H15/2) and the 572-nm yellow emission (4 F9/2→6 H13/2). TL spectra shows that the introduction of Dy3+ ions into the SrSiO3 host produces a highly dense trapping level at 377K (0.59eV), which is responsible for the long-lasting phosphorescence at room temperature. A possible mechanism of the long-lasting phosphorescence based on the experimental results is proposed. It is considered that the long-lasting phosphorescence is due to persistent energy transfer from the electron traps to the Dy3+ ions, which creates the persistent luminescence of Dy3+ to produce the white light-emitting long-lasting phosphorescence.Long-lasting phosphorescence spectra of SrSiO3:Dy3+ phosphor after the UV excited source has been removed at different times (λex=254nm,a=1,b=3,c=5min).
Keywords: Phosphor; Afterglow; Luminescence; SrSiO; 3; :Dy; 3+
Nitrogen-doped zirconia: A comparison with cation stabilized zirconia by Jong-Sook Lee; Martin Lerch; Joachim Maier (pp. 270-277).
The conductivity behavior of nitrogen-doped zirconia is compared with that of zirconia doped with lower-valent cations and discussed in the framework of defect–defect interactions. While nominally introducing the same number of vacancies as yttrium, nitrogen dopants introduced in the anion sublattice of zirconia lead to substantially different defect kinetics and energetics. Compared to the equivalent yttrium doping nitrogen doping in the Y–Zr–O–N system substantially increases the activation energy and correspondingly decreases the conductivity at temperatures below500∘C in the vacancy range below 4mol%. The comparison of N-doped zirconia and zirconia systems doped with size-matched cation stabilizers, such as Sc, Yb and Y, shows that elastically driven vacancy–vacancy ordering interactions can phenomenologically account for the temperature- and composition-dependence. It is striking that materials with superior high-temperature conductivities due to weak dopant–vacancy interactions undergo severe deterioration at low temperature due to the strong vacancy-ordering. The analysis also explains qualitatively similar effects of Y co-doping in Yb-, Sc-, and N-doped zirconia. Small amount of Y in N-doped zirconia as well as in Sc-doped zirconia appears to hinder the formation of the long-range ordered phase and thus enhance the conductivity substantially.Conductivity profiles in nitrogen-graded zirconia measured by microcontact impedance spectroscopy represented as a function of vacancy concentrations using the nitrogen concentration profiles determined by auger electron spectroscopy. The dotted region corresponds to the concentration step at the growth front bordering the TZP (tetragonal zirconia polycrystal) and large-grained PSZ (partially stabilized zirconia) region.
Keywords: Zirconia; Nitrogen; Conductivity; Vacancy ordering; Elastic defect interaction
Structural studies on W6+ and Nd3+ substituted La2Mo2O9 materials by Marrero-Lopez David Marrero-López; J. Canales-Vazquez Jesús Canales-Vázquez; Wuzong Zhou; John T.S. Irvine; Nunez Pedro Núñez (pp. 278-288).
The structure of a series of new ionic conductors based in lanthanum molybdate (La2Mo2O9) has been investigated using transmission electron microscopy (TEM), high-resolution X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The superstructure 2 ac×3 ac×4 ac of the low temperature α-polymorph relative to the β-polymorph was confirmed by HRTEM imaging and electron diffraction. Furthermore, the effects of partial cation substitution in the La2− xNd xMo2O9 and La2Mo2− yW yO9 series have been also evaluated in the search of new clues to understand the structure and stabilisation of the high temperature and better conductor β-polymorph. The thermal analysis studies show that Nd-substitution does not stabilise completely the β-polymorph at room temperature, although no superstructure ordering was observed by both XRD and HRTEM. On the other hand, W-substitution stabilises the cubic β-polymorph fory>0.25, although, electron diffraction indicates a slight distortion from the cubic symmetry for low W-content. This distortion disappears as the W content increases and the Rietveld refinements gradually render better results.Nd and W substituted La2Mo2O9 series were studied by XRD, TEM and thermal analysis to study the effects of substitution on the structure. The low temperature polymorph is a 2×3×4 superstructure of the high temperature polymorph. HRTEM images in the [001] and [001] zone axes for La2Mo2O9, showing very clearly the 2 ac×3 ac and 2 ac×4 ac superstructure, respectively.
Keywords: La; 2; Mo; 2; O; 9; Ionic conductor; HRTEM; Superstructure; Phase transition
Synthesis and crystal structures of CaY2Ge3O10 and CaY2Ge4O12 by Hisanori Yamane; Ryouji Tanimura; Takahiro Yamada; Junichi Takahashi; Takashi Kajiwara; Masahiko Shimada (pp. 289-295).
New compounds CaY2Ge3O10 and CaY2Ge4O12 were prepared by heating mixtures of CaCO3, Y2O3 and GeO2 at 1200°C. CaY2Ge3O10 is stable at 1300°C, while CaY2Ge4O12 decomposes into a melt and CaY2Ge3O10 at approximately 1250°C. We obtained single crystals of CaY2Ge3O10 by cooling a sample with an initial composition of Ca:Y:Ge=1:2:8 from 1300°C with a rate of −6°C/h. The crystal structure of CaY2Ge3O10 was determined by single crystal X-ray diffraction. CaY2Ge3O10 crystallizes in the monoclinic space groupP21/c witha=6.0906(8),b=6.8329(8),c=18.752(2)Å andβ=109.140(3)°,Z=4, andR1=0.029 forI>2σ(I). In the structure of CaY2Ge3O10, Ca and Y atoms are situated disorderly in three 7-fold coordination sites between isolated germanate groups of triple GeO4 tetrahedra, Ge3O10. The structural formula of CaY2Ge3O10 is expressed as (Ca0.45Y0.55)(Ca0.46Y0.54)(Ca0.09Y0.91)Ge3O10. The crystal structure of CaY2Ge4O12 was analyzed by the Rietveld method for the X-ray powder diffraction pattern. CaY2Ge4O12 is isotypic with SrNa2P4O12, crystallizing in the orthorhombic space group P4/ nbm,a=9.99282(6),c=5.06701(4)Å,Z=2,Rwp=0.092,Rp=0.067. CaY2Ge4O12 contains four-membered GeO4-tetrahedra rings, Ge4O12. Eight-fold coordinated square-anitiprism sites and 6-fold octahedral sites between the layers of the Ge4O12 rings are occupied by Y atom and Ca/Y atoms, respectively The structural formula is Y(Ca0.5Y0.5)2Ge4O12.Crystal structure of CaY2Ge3O10 showing Ge–O4 tetrahedra (Ge3O10 group).
Keywords: Calcium yttrium germanates; Crystal structure; X-ray diffraction; Germanate group
New mixed-valence chromium structure type: NH4Cr(CrO4)2 by Barbara M. Casari; Erica Wingstrand; Vratislav Langer (pp. 296-301).
Synthesis and crystal structure of a new structure type of mixed Cr(III)/Cr(VI) chromates is reported. NH4Cr(CrO4)2 was prepared from CrO3 in the presence of (NH4)2Ce(NO3)6. Since this is the first preparation of mixed valence ternary chromium oxides from aqueous solution, a reaction pathway for this synthesis is suggested. The crystal structure of NH4Cr(CrO4)2 has been determined from three-dimensional X-ray data collected at low temperature, 173K. The structure belongs to the orthorhombic space group Pnma, witha=14.5206(10),b=5.4826(4),c=8.7041(7)Å andZ=4. The title compound consists of corner-sharing chromium(III) octahedra and chromium(VI) tetrahedra forming a three-dimensional network with the composition [Cr(CrO4)2]n n–, containing channels in which zigzag rows of ammonium ions balance the net charge.The title compound constitutes a new structure type among the Cr(III)/Cr(VI) ternary oxides, the NH4-type. The other structure types are forming layers intercalated by the counter ions, while the structure of NH4Cr3O8 forms channels containing the ammonium ions.
Keywords: NH; 4; Cr; 3; O; 8; Mixed-valence ternary oxide; Mixed-valence chromate; Cr(VI)/Ce(III) redox reaction; X-ray diffraction
Solvothermal synthesis and characterisation of new one-dimensional indium and gallium sulphides: [C10N4H26]0.5[InS2] and [C10N4H26]0.5[GaS2] by Paz Vaqueiro (pp. 302-307).
Two new main group metal sulphides, [C10N4H26]0.5[InS2] (1) and [C10N4H26]0.5[GaS2] (2) have been prepared solvothermally in the presence of 1,4-bis(3-aminopropyl)piperazine and their crystal structures determined by single-crystal X-ray diffraction. Both compounds are isostructural and crystallise in the monoclinic space groupP21 /n (Z=4), with a=6.5628(5), b=11.2008(9), c=12.6611(9) Å and β=94.410(4)° (w R=0.035) for compound (1) and a=6.1094(5), b=11.2469(9), c=12.7064(10) Å and β=94.313(4)° (w R=0.021) for compound (2). The structure of [C10N4H26]0.5[ MS2] ( M=In,Ga) consists of one-dimensional [ MS2]− chains which run parallel to the crystallographic a axis and are separated by diprotonated amine molecules. These materials represent the first example of solvothermally prepared one-dimensional gallium and indium sulphides.[C10N4H26]0.5[InS2] and [C10N4H26]0.5[GaS2], prepared under solvothermal conditions, consist of one-dimensional [ MS2]− chains separated by diprotonated 1,4-bis(3-aminopropyl)piperazine molecules.
Keywords: Solvothermal synthesis; Crystal structure; Indium sulphides; Gallium sulphides
Preparation and characterization of LiNi0.8Co0.2O2/PANI microcomposite electrode materials under assisted ultrasonic irradiation by Y. Mosqueda; Perez-Cappe E. Pérez-Cappe; J. Arana; E. Longo; A. Ries; M. Cilense; P.A.P. Nascente; P. Aranda; E. Ruiz-Hitzky (pp. 308-314).
A preparation method for a new electrode material based on the LiNi0.8Co0.2O2/polyaniline (PANI) composite is reported. This material is prepared by in situ polymerization of aniline in the presence of LiNi0.8Co0.2O2 assisted by ultrasonic irradiation. The materials are characterized by XRD, TG-DTA, FTIR, XPS, SEM-EDX, AFM, nitrogen adsorption (BET surface area) and electrical conductivity measurements. PANI in the emeraldine salt form interacts with metal-oxide particles to assure good connectivity. The dc electrical conductivity measurements at room temperature indicate that conductivity values are one order of magnitude higher in the composite than in the oxide alone. This behavior determines better reversibility for Li-insertion in charge–discharge cycles compared to the pristine mixed oxide when used as electrode of lithium batteries.PANI/LiNi0.8Co0.2O2 microcomposites prepared under ultrasound irradiation are formed by oxide particles in contact with the conducting polymer procuring connectivity that enhances electrical and electrochemical properties of the resulting materials.
Keywords: PANI; Ni–Co mixed oxides; Organic–inorganic composites; Electrode materials; Lithium batteries
The reciprocal CuInS2+2CdSe⇔CuInSe2+2CdS system. Part I. The quasi-binary CuInSe2–CdSe system: Phase diagram and crystal structure of solid solutions by I.D. Olekseyuk; O.V. Parasyuk; O.A. Dzham; L.V. Piskach (pp. 315-322).
The type of interaction in quasi-binary system CuInSe2 (CIS)–CdSe was investigated using differential thermal and X-ray phase analysis methods. The limits of existence of solid solutions based on low-temperature ( α) and high-temperature ( γ) CIS modifications and CdSe ( β) with chalcopyrite, sphalerite and wurtzite structures, respectively, were established in sub-solidus region at 620K and 870K. For certain compositions of solid solutions, the structure was refined using powder X-ray diffraction. A phase diagram of the CIS–CdSe system was constructed. A peritectic process L+ β⇔γ takes place in the system at 1260K.Display Omitted
Keywords: Semiconductors; Liquid–solid reaction; Phase diagrams; Thermal analysis
Mechanochemical synthesis and ionic conductivity in the Gd2(Sn1– yZr y)2O7 (0⩽y⩽1) solid solution by K.J. Moreno; A.F. Fuentes; Garcia-Barriocanal J. García-Barriocanal; Leon C. León; Santamaria J. Santamaría (pp. 323-330).
Several compositions within the Gd2(Sn1− yZr y)2O7 solid solution with a pyrochlore-type of structure, have been prepared at room temperature in a planetary ball mill starting from stoichiometric mixtures of the constituent oxides, SnO2, ZrO2 and Gd2O3. Phase evolution in the powder mixtures as a function of composition and milling time was followed by X-ray diffraction (XRD) finding out that after 18h, every mixture consist of a single phase. Mechanically activated chemical reaction takes place after an intial step of particle size refinement and polymorphic transformation of C-Gd2O3. We have performed Impedance Spectroscopy measurements to investigate oxygen ion dynamics in the series and conclude that Zr substitution for Sn hardly modifies the importance of ion–ion correlations in the oxygen diffusion process. We also estimate from conductivity measurements the value of the microscopic activation energy needed for independent ion hopping, which is found to be 0.56±0.06eV, independent of Zr content.Macroscopic ( Edc, empty squares) and microscopic ( Ea, solid squares) activation energies for oxygen ion migration as a function of Zr content, for the Gd2(Sn(1− y)Zr y)2O7 solid solution. Inset: DRX patterns of several compositions in the title solid solution with different Sn/Zr ratio.
Keywords: Pyrochlores; Ionic conductivity; Mechanochemical synthesis; Dielectric relaxation; Impedance spectroscopy
The role of NH3 atmosphere in preparing nitrogen-doped TiO2 by mechanochemical reaction by Gang Liu; Feng Li; Zhigang Chen; Gao Qing Lu; H.-M. Hui-Ming Cheng (pp. 331-335).
NH3 atmosphere in ball milling plays an important role in preparing TiO2− XN X by a simple mechanochemical reaction. The results show that the structure transformation of titania milled in NH3 is greatly delayed compared with that in air. The specific surface area of titania milled in NH3 for 2h is two times larger than that in air. It was also found that titania prepared in NH3 has obvious absorbance for visible light. Mechanochemical milling in NH3 atmosphere offers a new route to prepare TiO2− XN X with high surface area.The specific surface area (BET) of titania varies with the increase of milling time in air and gaseous ammonia.
Keywords: Titania; Nitrogen doping; Mechanochemical reaction; Phase transformation; Visible light absorption
Crystal structure of the pyrochlore oxide superconductor KOs2O6 by J.-I. Jun-Ichi Yamaura; Shigeki Yonezawa; Yuji Muraoka; Zenji Hiroi (pp. 336-340).
We report the single-crystal X-ray analysis of the structure of the pyrochlore oxide superconductor KOs2O6. The structure was identified as theβ-pyrochlore structure with space groupFd3¯m and lattice constanta=10.089(2)Å at300K: the K atom is located at the8b site, not at the16d site as in conventional pyrochlore oxides. We found an anomalously large atomic displacement parameterUiso=0.0735(8)Å2 at300K for the K cation, which suggests that the K cation weakly bound to an oversized Os12O18 cage exhibits intensive rattling, as recently observed for clathrate compounds. The rattling of A cations is a common feature in the series ofβ-pyrochlore oxide superconductors AOs2O6 (A=Cs, Rb and K), and is greatest for the smallest K cation.Crystal structure ofβ-pyrochlore oxide KOs2O6. Corner-shared OsO6 octahedra form a three-dimensional network involving large atomic cage, and a K atom in each cage constitutes a ’hypothetical’ diamond lattice.
Keywords: PACS; 64.10.Nz; 63.20.Pw; 63.20.Ry; 74.70.DdPyrochlore oxides; Superconductor; Crystal structure; Rattling