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1.
Dirubidium calcium tetraborate octahydrate, Rb2Ca[B4O5(OH)4]2·8H2O, was prepared by reaction of Rb-borate aqueous solution with CaCl2 and it's structure has been determined by single-crystal X-ray diffraction data. It crystallizes in the orthorhombic system, space group P212121 with unit cell parameters, Z=4, The structure contains alternate layers of [B4O5(OH)4]2− polyanions separated by water molecules and Rb, Ca cations. The isolated [B4O5(OH)4]2− is constructed from two BO3(OH) tetrahedron groups and two BO2(OH) triangular groups joined at common oxygen atoms. The two BO3(OH) tetrahedron groups are further linked by means of an oxygen bridge across the ring. The Ca2+ ion displays seven coordination, while the two non-equivalent Rb+ ions display nine and seven coordination, respectively. Infrared and Raman (4000-400 cm−1) spectra of Rb2Ca[B4O5(OH)4]2·8H2O were recorded at room temperature and analyzed. Fundamental vibrational modes were identified and band assignments were made. The dehydration of this hydrated mixed borate occurs in one step and leads to an amorphous phase which undergoes a crystallization. 相似文献
2.
Daniel E. Bugaris 《Journal of solid state chemistry》2008,181(12):3189-3193
Two new quaternary salts, [Hg3Te2][UCl6] and [Hg4As2][UCl6], have been synthesized and their structures determined by single-crystal X-ray diffraction analysis. [Hg3Te2][UCl6] is the product of a reaction involving UCl4, HgCl2, and HgTe at 873 K. The compound crystallizes in space group P21/c of the monoclinic system. [Hg4As2][UCl6] results from the reaction of U, Hg2Cl2, and As at 788 K. It crystallizes in space group Pbca of the orthorhombic system. [Hg3Te2][UCl6] has a two-dimensional framework of layers, whereas [Hg4As2][UCl6] has a three-dimensional framework of layers interconnected by Hg atoms linearly bonded to As atoms. Both framework structures contain discrete [UCl6]2− anions between the layers. [Hg3Te2][UCl6] exhibits temperature-independent paramagnetism. The optical absorption spectra of these compounds display f-f transitions. 相似文献
3.
Abdeljalil Assoud 《Journal of solid state chemistry》2006,179(8):2707-2713
The title compounds were prepared from the elements in the stoichiometric ratio at 800 °C under exclusion of air. Tl6Si2Te6 crystallizes in the space group P1¯, isostructural with Tl6Ge2Te6, with , , , α=89.158(2)°, β=96.544(2)°, γ=100.685(2)°, (Z=2). Its structure is composed of dimeric [Si2Te6]6− units with a Si-Si single bond, while the Tl atoms are irregularly coordinated by five to six Te atoms. Numerous weakly bonding Tl-Tl contacts exist. Both title compounds are black semiconductors with small band gaps, calculated to be 0.9 eV for Tl6Si2Te6 and 0.5 eV for Tl6Ge2Te6. The Seebeck coefficients are +65 μV K−1 in case of Tl6Si2Te6 and +150 μV K−1 in case of Tl6Ge2Te6 at 300 K, and the electrical conductivities are 5.5 and 3 Ω−1 cm−1, respectively. 相似文献
4.
Takeshi Suzuyama Hiroki Yamamoto Masakazu Ito Takao Nakama Shoichi Nagata 《Journal of solid state chemistry》2006,179(1):140-144
Ferromagnetic-phase transition in spinel-type CuCr2Te4 has been clearly observed. CuCr2Te4 is a telluride-spinel with the lattice constant , which has been synthesized successfully. The heat capacity exhibits a sharp peak due to the ferromagnetic-phase transition with the Curie temperature . This value of TC corresponds exactly to that of the negative peak of dM/dT in low field of 1.0 Oe. The magnetic susceptibility shows the Curie-Weiss behavior between 380 and 650 K with the effective magnetic moment /Cr-ion and the Weiss constant . 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 250 K which is a fairly high temperature. 相似文献
5.
M.P. Crosnier-Lopez M. Barre F. Le Berre J.L. Fourquet 《Journal of solid state chemistry》2006,179(8):2714-2720
The La1/3Zr2(PO4)3 NASICON-type compound (S.G. - neutron and X-ray diffraction experiments) is investigated by transmission electron microscopy (TEM) technique, selected area electron diffraction (SAED) and high-resolution electron microscopy (HREM), in order to study locally the lanthanum distribution. An irreversible structural transformation is observed, without modification of the atomic content and cell size, as soon as the phase is illuminated by the electron beam. The progressive disappearance of the spots which do not check the R conditions on the SAED patterns is clearly shown along two zone axis, [001] and [100]. This transformation implies the displacement of the two La3+ cations in a preserved classical [Zr2(PO4)3]− network. This interesting behavior is in good agreement with the La3+ ionic conductivity observed in La1/3Zr2(PO4)3 (4.09×10−7 S cm−1 at 700 °C). To our knowledge, this is the first time that a complete TEM study is done on a NASICON-type phase. 相似文献
6.
Rare earth ions (Eu3+ and Dy3+)-doped Gd2(WO4)3 phosphor films were prepared by a Pechini sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM) and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting powders and films. The results of XRD indicate that the films begin to crystallize at 600°C and the crystallinity increases with the elevation of annealing temperatures. The film is uniform and crack-free, mainly consists of closely packed fine particles with an average grain size of 80 nm. Owing to an energy transfer from WO42− groups, the rare earth ions show their characteristic emissions in crystalline Gd2(WO4)3 phosphor films, i.e., (J=0, 1, 2, 3; J′=0, 1, 2, 3, 4, not in all cases) transitions for Eu3+ and (J=13/2, 15/2) transitions for Dy3+, with the hypersensitive transitions (Eu3+) and (Dy3+) being the most prominent groups, respectively. Both the lifetimes and PL intensity of the Eu3+ () and Dy3+ () increase with increasing the annealing temperature from 500°C to 800°C, and the optimum doping concentrations for Eu3+ and Dy3+ are determined to be 30 and 6 at% of Gd3+ in Gd2(WO4)3 film host lattices, respectively. 相似文献
7.
M Karbowiak 《Journal of solid state chemistry》2004,177(7):2415-2422
Temperature-dependent line broadening measurements of emission and excitation transitions for two intrinsic sites U(1) and U(2) of U3+ ions doped in a RbY2Cl7 single crystals as well as of U4+ ions have been performed. Values of the electron phonon (EP) coupling parameter were determined by a fit of experimentally observed line widths to an equation containing the temperature dependent broadening term due to the Raman two-phonon process. The parameters for U3+ ions in RbY2Cl7 are larger than those determined for this ion in LaCl3 host crystals. This is due to shorter M-Cl distances in RbY2Cl7 which leads to a stronger interaction of uranium with the chlorine ions and to an increase of covalency. The relatively large value determined for the multiplet of U3+ in RbY2Cl7 may result from the proximity of opposite parity 5f26d1 states. The parameters obtained for the U3+ ions are larger than those for U4+. The latter ones are affected by a stronger crystal-field (CF), however the position of the first 5f26d1 or 5f16d1 states, which for U3+ is observed at an energy of ∼15,000 cm−1 lower than for U4+, is the dominating one among the factors influencing the EP coupling strength. The EP coupling parameters for all investigated transitions of the U3+ ions are larger for U(2) than for U(1), which results mainly from the larger crystal field strength observed for the U(2) site. The differences in the EP coupling strength of the U3+ ions in the U(1) and U(2) sites are in accordance with decay times observed for emission for both sites from the multiplet. 相似文献
8.
9.
Single crystals of Sb2−xFexTe3 (cFe=0-9.5×1019 cm−3) were prepared by Bridgman method. The interpretation of the reflection spectra in plasma resonance region indicates that Fe increases the concentration of holes (acceptor) and each Fe atom incorporated in Sb2Te3 structure liberates 0.4-0.5 hole. Observed effect is elucidated by means of point defect model. According to the model Fe atoms enter the structure and form uncharged substitutional defects . Since this defect cannot affect the free-carrier concentration directly, we assume an interaction of the entering Fe-atoms with natives defects leading to a rise in the concentration of antisite defects , to a decrease of concentration, and to an increase in the concentration of holes. 相似文献
10.
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 with . Na2.7Ru4O9 is paramagnetic, χ0= with and a Curie constant of 0.0119 emu/mol Oe K. 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 be15 mJ/moleRu K2. 相似文献
11.
G. Haxhillazi 《Journal of solid state chemistry》2004,177(9):3045-3051
The compounds (NH4)3[Ta(O2)4], K3[Ta(O2)4], Rb3[Ta(O2)4] and Cs3[Ta(O2)4] have been prepared and investigated by X-ray powder methods as well as Raman- and IR-spectroscopy. In the case of Rb3[Ta(O2)4] the structure has been solved from single crystal data. It is shown that all these compounds are isotypic and crystallize in the K3[Cr(O2)4] type (SG , No. 121). The infrared- and Raman spectra (recorded on powdered samples) are discussed with respect to the internal vibrations of the peroxo-group and the dodecahedral [Ta(O2)4]3− ion. Symmetry coordinates for the [Ta(O2)4]3− ion are given from which the vibrational modes of the O-O stretching vibrations of the O22− groups, the Ta-O stretching vibrations and the Ta-O bending vibrations are deduced. 相似文献
12.
The new compound Sr5(As2O7)2(AsO3OH) was synthesized under hydrothermal conditions. It represents a previously unknown structure type and belongs to a group of a few compounds in the system SrO-As2O5-H2O; (As2O7)4− besides (AsO3OH)2− groups have not been described yet. The crystal structure of Sr5(As2O7)2(AsO3OH) was determined by single-crystal X-ray diffraction (space group P21/n, a=7.146(1), b=7.142(1), , β=93.67(3)°, , Z=4). One of the five symmetrically unique Sr atoms is in a trigonal antiprismatic (Inorg. Chem. 35 (1996) 4708)—coordination, whereas the other Sr atoms adopt the commonly observed (“Collect” data collection software, Delft, The Netherlands, 1999; Methods Enzymol. 276 (1997) 307)—coordination. The position of the hydrogen atom was located in a difference Fourier map and subsequently refined with an isotropic displacement parameter. Worth mentioning is the very short hydrogen bond length Oh-H?O(1) of 2.494(4) Å; it belongs to the shortest known examples where the donor and acceptor atoms are crystallographically different. This hydrogen bond was confirmed by IR spectroscopy. In addition, Raman spectra were collected in order to study the arsenate groups. 相似文献
13.
Kenny Ståhl Tonci Balic-Zunic K. Michael Eriksen Rasmus Fehrmann 《Journal of solid state chemistry》2005,178(5):1697-1704
The crystal structures of K2S2O7, KNaS2O7 and Na2S2O7 have been solved and/or refined from X-ray synchrotron powder diffraction data and conventional single-crystal data. K2S2O7: From powder diffraction data, monoclinic C2/c, Z=4, a=12.3653(2), b=7.3122(1), , β=93.0792(7)°, RBragg=0.096. KNaS2O7: From powder diffraction data; triclinic , Z=2, a=5.90476(9), b=7.2008(1), , α=101.7074(9), β=90.6960(7), γ=94.2403(9)°, RBragg=0.075. Na2S2O7: From single-crystal data; triclinic , Z=2, a=6.7702(9), b=6.7975(10), , α=116.779(2), β=96.089(3), γ=84.000(3)°, RF=0.033. The disulphate anions are essentially eclipsed. All three structures can be described as dichromate-like, where the alkali cations coordinate oxygens of the isolated disulphate groups in three-dimensional networks. The K-O and Na-O coordinations were determined from electron density topology and coordination geometry. The three structures have a cation-disulphate chain in common. In K2S2O7 and Na2S2O7 the neighbouring chains are antiparallel, while in KNaS2O7 the chains are parallel. The differences between the K2S2O7 and Na2S2O7 structures, with double-, respectively single-sided chain connections and straight, respectively, corrugated structural layers can be understood in terms of the differences in size and coordinating ability of the cations. 相似文献
14.
The crystal structures of three new intermetallic ternary compounds in the LnNiSb3 (Ln=Pr, Nd and Sm) family have been characterized by single crystal X-ray diffraction. PrNiSb3, NdNiSb3 and SmNiSb3 all crystallize in an orthorhombic space group, Pbcm (No. 57), Z=12, with , , , and ; , , , and ; and , , , and , for Ln=Pr, Nd and Sm, respectively. These compounds consist of rare-earth atoms located above and below layers of nearly square, buckled Sb nets, along with layers of highly distorted edge- and face-sharing NiSb6 octahedra. Resistivity data indicate metallic behavior for all three compounds. Magnetization measurements show antiferromagnetic behavior with (PrNiSb3), 4.6 K (NdNiSb3), and 2.9 K (SmNiSb3). Effective moments of 3.62 μB, 3.90 μB and 0.80 μB are found for PrNiSb3, NdNiSb3 and SmNiSb3, respectively, and are consistent with Pr3+ (f 2), Nd3+ (f 3), and Sm3+ (f 4). 相似文献
15.
M. Karbowiak 《Journal of solid state chemistry》2003,173(1):59-68
Temperature-dependent line width and line shift measurements between 7 and 280 K have been performed for a number of absorption transitions in the 4000-21,000 cm−1 energy range of the U3+:LaCl3, Nd3+:LaCl3 and U3+:LaBr3 single crystal spectra. The values of the electron-phonon coupling parameter were determined for U3+:LaCl3 and Nd3+:LaCl3 by a fit of experimentally observed line widths to an equation containing the temperature dependent broadening due to the Raman two-phonon process. For both ions diluted in LaCl3 the values of the parameters are considerably lower than in K2LaCl5, and the value of for U3+ in the LaCl3 host is markedly larger as compared with that of Nd3+. Factors influencing these differences are discussed. With a temperature increase a blue shift of the absorption lines of the U3+ ions in LaCl3 and LaBr3 is observed. A comparison has been performed among the electron-phonon coupling parameters obtained from an analysis of the line widths of the U3+:LaCl3 single crystal and those determined from temperature induced line shifts as well as between the magnitudes of the absolute increase in line width and line shifts in the 7-290 K temperature range for U3+ doped LaCl3 and LaBr3 crystals. The electron-phonon coupling is stronger for U3+ in the tribromide as compared with the trichloride host which is mainly due to a larger covalency of the first one. 相似文献
16.
E. Moreira D.L. Azevedo E.W.S. Caetano V.N. Freire 《Journal of solid state chemistry》2011,184(4):921-928
Orthorhombic SrSnO3 was investigated using density functional theory (DFT) considering both the local density and generalized gradient approximations, LDA and GGA, respectively. The electronic band structure, density of states, complex dielectric function, optical absorption, and the infrared and Raman spectra were computed. Calculated lattice parameters are close to the experimental measurements, and an indirect band gap (2.27 eV) was obtained within the GGA (LDA) level of calculation. Effective masses for holes and electrons were estimated, being very anisotropic in comparison with similar results for orthorhombic CaSnO3. The complex dielectric function and the optical absorption of SrSnO3 were shown to be sensitive to the plane of polarization of the incident light. The infrared spectrum between 100 and 600 cm−1 was obtained, with its main peaks being assigned, and a nice agreement between experimental and theoretical peaks of the Raman spectrum of orthorhombic SrSnO3 was achieved. 相似文献
17.
The enthalpies of dilution have been measured for aqueous Li2B4O7 solutions from 0.0212 to 2.1530 mol kg−1 at 298.15 K. The relative apparent molar enthalpies, L?, and relative partial molar enthalpies of the solvent and solute, and were calculated. The thermodynamic properties of the complex aqueous solutions were represented with a modified Pitzer ion-interaction model. 相似文献
18.
The novel compound Ca2Co1.6Ga0.4O5 with brownmillerite (BM) structure has been prepared from citrates at 950 °C. The crystal structure of Ca2Co1.6Ga0.4O5 was refined, from neutron powder diffraction (NPD) data, in space group Pnma, , , , χ2=1.798, , Rwp=0.0378 and Rp=0.0292. On the basis of the NPD refinement the compound was found to be a G-type antiferromagnet (space group Pn′m′a) at room temperature, with the magnetic moments of cobalt atoms directed along chains of tetrahedra in the BM structure. Electron diffraction and electron microscopy studies revealed disorder in the crystallites, which can be interpreted as the presence of slabs with BM-type structure of Pnma and I2mb symmetry. 相似文献
19.
A novel non-centrosymmetric borate, BiCd3(AlO)3(BO3)4, has been prepared by solid state reaction methods below 750 °C. Single-crystal XRD analysis showed that it crystallizes in the hexagonal group P63 with a=10.3919(15) Å, c=5.7215(11) Å, Z=2. In its structure, AlO6 octahedra share edges to form 1D chains that are bridged by BO3 groups through sharing O atoms to form the 3D framework. The 3D framework affords two kinds of channels that are occupied by Bi3+/Cd2+ atoms only or by Bi3+/Cd2+ atoms together with BO3 groups. The IR spectrum further confirmed the presence of BO3 groups. Second-harmonic-generation measurements displayed a response of about 0.5×KDP (KH2PO4). UV-vis diffuse reflectance spectrum showed a band gap of about 3.19 eV. Solid-state fluorescence spectrum exhibited the maximum emission peak at around 390.6 nm. Band structure calculations indicated that it is an indirect semiconductor. 相似文献
20.
Catherine Renard Pascal Roussel Annick Rubbens Sylvie Daviero-Minaud Francis Abraham 《Journal of solid state chemistry》2006,179(7):2101-2110
We report the synthesis and crystal structure of the new compound Sr4PbPt4O11, containing platinum in highly unusual square pyramidal coordination. The crystals were obtained in molten lead oxide. The structure was solved by X-ray single crystal diffraction techniques on a twinned sample, the final R factors are R=0.0260 and wR=0.0262. The symmetry is triclinic, space group P1¯, with , , , α=90.421(3)°, β=89.773(8)°, γ=90.140(9)° and Z=2. The structure is built from dumbell-shaped Pt2O9 entities formed by a dinuclear metal-metal bonded Pt26+ ion with asymmetric environments of the two Pt atoms, classical PtO4 square plane and unusual PtO5 square pyramid. Successive Pt2O9 entities deduced from 90° rotations are connected through the oxygens of the PtO4 basal squares to form [Pt4O108−]∞ columns further connected through Pb2+ and Sr2+ ions. Raman spectroscopy confirmed the peculiar platinum coordination environment. 相似文献