European Journal of Solid State and Inorganic Chemistry最新文献

Crystals of sodium doped lanthanum orthomanganites were grown for the first time in sodium chloride flux at 900°C. 0.5 to 0.1mm size crystals were isolated. Composition of the oxide, La_0.82Na_0.13MnO_2.93 was arrived at by chemical analysis of the elements present. Single crystal X-ray structural study showed that the lanthanum as well as oxygen site deficient orthomanganites crystallize in R3¯ space group unlike many divalent cation doped lanthanum orthomanganites which crystallize in R3¯.

Dicopper diacetylide Cu-C≡C-C≡C-Cu, prepared from butadiyne has been studied by FT-IR spectroscopy in comparison to dicopper acetylide Cu-C≡C-Cu. Upon ageing by exposure to air at room temperature, Cu-C≡C-Cu has been transformed into Cu-C≡C-C≡C-Cu as demonstrated by FT-IR spectroscopy and this compound is further transformed on standing in air. A special kind of solid state oxidative coupling reaction occurs so that polyynes chains are formed in these aged solids. It is shown that the FT-IR spectrum of copper acetylide prepared from ammonia solutions of Cu⁺ and Cu²⁺ ions is comparable to that of air oxidized Cu-C≡C-Cu (and Cu-C≡C-C≡C-Cu) prepared exclusively from Cu⁺ ions in presence of a reducing agent demonstrating that Cu²⁺ ions display the same oxidizing effect as oxygen causing coupling reactions in solution and producing Cu-C≡C-C≡C-Cu.

Cu-C≡C-Cu oxidized at 60–70°C with CuCl₂ produces a product which could be formulated as Cu(C≡C)₂₀Cu; FT-IR absorption at 1950 cm⁻¹ could suggest the presence of cumulenic carbon chain although acetylenic carbon chains cannot be excluded completely.

α-NaCaAlF₆ is prepared by solid state reaction as poor quality crystals. The structure is determined ab initio from conventional X-ray powder data. The cell is monoclinic, space group P2₁/c, Z = 8, with a = 8.7423(3) Å, b = 5.1927(2) Å, c = 20.3514(9) Å and β = 91.499(2)°. The final Rietveld refinement leads to R_P = 10.6% and R_B = 5.2 %. The structure is built up from isolated AlF₆ octahedra, interconnected by CaF₇ polyhedra sandwiched between layers of NaF₈ and NaF₇ polyhedra extending in the be plane.

Preparation, characterization by X-ray diffraction, IR absorption, DTATG analysis, and ab-initio crystal structure determination are reported for anhydrous lithium cyclohexaphosphate Li₆P₆O₁₈. It crystallizes in a monoclinic cell (space group P2₁/n N^o14, Z=2) with a = 7.9911(3)Å, b = 17.0319(6)Å, c = 5.3208(2)Å and β = 99.433(1)°. X-ray powder diffraction data were fitted by Rietveld method leading to R_Bragg = 0.034. The crystal structure of Li₆P₆O₁₈ is built up from P₆O₁₈ ring anions, with 1 internal symmetry. Six lithium coordination polyhedra (two pseudo square pyramids and four tetrahedra) share common edges and corners as to form Li₆O₁₆ groups. These cationic groups build up a layer in the (1 0 1¯) plane showing large distorted hexagonal tunnels and interconnect the P₆O₁₈ rings in a three dimensional way.

A calcining at 300°C and sintering process were proposed to obtain a pure perovskite phase Pb(Fe_1/2 Nb_1/2)O₃ from a 4PbO/Nb₂O₅/Fe₂O₃ mixture, which is calcined at 300°C for several days and sintered at various temperatures for 2h; the resultant powder was air quenched. The X-ray powder diffraction pattern of the sintered sample is carefully analyzed to identify intermediate phases. The effects of calcining at 300°C and sintering on obtaining PFN are based on the deformation of Pb₅Fe₄Nb₄O₂₁. A reaction mechanism for the calcining cycle of Pb(Fe_1/2 Nb_1/2)O₃ is proposed.

Spray pyrolysis process has been used to deposit highly transparent and conducting films of tin doped indium oxide onto glass substrates. The electrical, optical and structural properties have been investigated as a function of various deposition parameters namely dopant concentrations, temperature and nature of substrates. X-ray diffraction patterns have shown that deposited films are polycrystalline without second phases and have preferred orientation [400]. Indium tin oxide layers with small resistivity value around 7.10⁻⁵Ω.cm and transmission coefficient in the visible and near IR range of about 85–90 % have been easily obtained.

The structure of monoaquabis(pyridine)bis(saccharinato)copper(II), [Cu(H₂O)(py)₂(sac)₂], has been investigated by X-ray diffraction and infrared spectroscopy. The complex crystallizes in the orthorhombic space group I bat2 with the following unit cell parameters: a = 9.4874(7), b = 21.545(1), c = 13.164(1) Å, V= 2690.8(4) ų, D_c = 1.491 g cm⁻³, Z = 4, R = 0.025, wR = 0.036. The structure consists of individual [Cu(H₂O)(py)₂(sac)₂] molecules. The copper atom is bonded to two pyridine and two saccharinato nitrogen atoms as well as to the water oxygen atom forming a distorted square pyramid. The copper atom lying on a twofold rotation axis is 0.2209(7) Å above the basis square plane formed by the four nitrogen atoms. The bond distances in the coordination polyhedron are: Cu-N11 2.032(2) Å, Cu-N21 2.040(2) Å, Cu-OW1 2.177(2) Å. The N-Cu-N angles amount 88.67(8)° and 89.97(8)° as well as 167.36(9) and 167.69(8)°, while the values of the OW1-Cu-N angles are 96.16(6)° and 96.32(6)°. The FT infrared spectral features in the region of the OH, OD, CO and SO₂ stretching vibrations are discussed and correlated with the data obtained by X-ray diffraction.

A brief overview on two novel spray pyrolysis techniques developed recently in our laboratory, i.e. Electrostatic Spray Deposition (ESD) and Flame-Assisted Ultrasonic Spray Pyrolysis (FAUSP), is presented in this paper. Alcoholic solutions of metal salts or alkoxides are used as precursor solutions. Both techniques have been successfully applied to synthesize electroceramic materials including semiconductor TiO₂, ionic conductor ZrO₂, and mixed electronic-ionic conductor LiMn₂O₄. ESD is usually used for the fabrication of thin films with various morphologies, while FAUSP is used for the production of fine powders.

The sequence of phase transitions in the system La₂O₃-MO(MCO₃)Mn₂O₃, (M=Ca, Sr, Ba, Cd) and the span range of La_1−xM_xMnO_3±δ solid solutions formed were studied. It is demonstrated that interaction begins at 650°C due to formation of divalent metal manganites. Just simultaneously as a result of oxidation-reduction processes and structural transformations the synthesis of small quantities of solid solutions takes place, which is kinetically favoured in the case of smaller divalent metal cations. The chemical transformation finishes at 1200°C. The values of x at all systems are near 0,35. The absence of CdMnO₃ composition in the system CdO-MnO is proved.

The title compound has been prepared by hydrothermal synthesis and its crystal structure was determined by single crystal X-ray diffraction: space group P2₁/m, a = 4.8890(2), b = 14.3857(5), c = 7.9017(3) Å, β = 90.134(4)°, wR₂ = 0.123, R = 0.045. Cu²⁺ has two different coordination polyhedra: an elongated square pyramidal [CuFO₄] and square planar [CuO₄] coordination in a 2:1 ratio. Edge-sharing double-pyramids and [CuO₄] squares form zig-zag chains interconnected by [ZnO₄] and [PO₄] tetrahedra to form an open anionic framework structure whose channels are occupied by the K⁺ ions.