共查询到20条相似文献,搜索用时 93 毫秒
1.
Alexander Gribanov Andriy Grytsiv Yurii Seropegin 《Journal of solid state chemistry》2010,183(6):1278-1289
Two series of intermetallic alloys, RT2Si and RTSi2, have been synthesized from stoichiometric compositions. The crystal structures of EuPt1+xSi2−x (CeNiSi2-type), CeIr2Si (new structure type), YbPd2Si and YbPt2Si (both YPd2Si-type) have been elucidated from X-ray single crystal CCD data, which were confirmed by XPD experiments. The crystal structures of LaRh2Si and LaIr2Si (CeIr2Si-type), {La,Ce,Pr,Nd}AgSi2 (all TbFeSi2-type), and EuPt2Si (inverse CeNiSi2-type) were characterized by XPD data. RT2Si/RTSi2 compounds were neither detected in as-cast alloys Sc25Pt50Si25, Eu25Os25Si50 and Eu25Rh25Si50 nor after annealing at 900 °C. Instead, X-ray single crystal data prompted Eu2Os3Si5 (Sc2Fe3Si5-type) and EuRh2+xSi2−x (x=0.04, ThCr2Si2-type) as well as a new structure type for Sc2Pt3Si2 (own type). 相似文献
2.
Shengfeng Liu 《Journal of solid state chemistry》2006,179(3):830-835
The title compounds were synthesized and characterized by structural measurements and electronic structure calculations. Single-crystal X-ray diffraction analyses established that they all have the orthorhombic inverse-PbCl2-type structure (Pnma, Z=4, a=8.108(2), 8.124(2), 8.421(2), 8.509(2) Å; b=4.944(1), 4.949(1), 5.168(1), 5.189(1) Å; c=9.170(2), 9.184(2), 9.685(2), 9.740(2) Å, respectively). The tetrel (Tt) atoms are situated in tricapped trigonal prisms of ordered Sr and Ca atoms in which the smaller Ca atoms play a distinctive role. The structure is distinguishable from the Co2Si type by its more nearly ideal 6+3 (TCTP) environment about Tt rather than a higher coordination by cations. Other representations of the two structural types are also considered. Electronic band structure calculations suggest that the compounds are semiconductors, in agreement with literature data on their Ae2Tt analogues. 相似文献
3.
Svilen Bobev Veronika Fritsch Joe D. Thompson 《Journal of solid state chemistry》2006,179(4):1035-1040
Two non-stoichiometric Gd compounds, GdCu5−xTrx (Tr=Al, Ga) have been synthesized from the corresponding elements by high temperature reactions in sealed tantalum containers. They crystallize in the hexagonal CaCu5-type (Pearson's symbol hP6, space group P6/mmm, No. 191) with lattice parameters determined from single-crystal X-ray diffraction at room temperature as follows: a=5.0831(10) Å; c=4.156(2) Å for GdCu3.98(4)Al1.02(4), and a=5.1025(10) Å; c=4.155(2) Å for GdCu3.9(1)Ga1.1(1), respectively. Structure refinements from single crystal X-ray diffraction data reveal that substitution of Cu for Al or Ga takes place preferably on one of the two transition metal sites with site symmetry mmm (3g). Both compounds order antiferromagnetically below ∼40 K and ∼36 K, respectively, as determined from temperature dependent dc-magnetization, resistivity and heat-capacity measurements. 相似文献
4.
O.L. Sologub L.P. Salamakha H. Noël A.P. Gonçalves 《Journal of solid state chemistry》2007,180(10):2740-2746
Two new compounds, La3Ru8B6 and Y3Os8B6, were synthesized by arc melting the elements. Their structural characterization was carried out at room temperature on as-cast samples by using X-ray diffractometry. According to X-ray single-crystal diffraction results these borides crystallize in Fmmm space group (no. 69), Z=4, a=5.5607(1) Å, b=9.8035(3) Å, c=17.5524(4) Å, ρ=8.956 Mg/m3, μ=25.23 mm−1 for La3Ru8B6 and a=5.4792(2) Å, b=9.5139(4) Å, c=17.6972(8) Å, ρ=13.343 Mg/m3, μ=128.23 mm−1 for Y3Os8B6. The crystal structure of La3Ru8B6 was confirmed from Rietveld refinement of X-ray powder diffraction data. Both La3Ru8B6 and Y3Os8B6 compounds are isotypic with the Ca3Rh8B6 compound and their structures are built up from CeCo3B2-type and CeAl2Ga2-type structural fragments taken in ratio 2:1. They are the members of structural series R(A)nM3n−1B2n with n=3 (R is the rare earth metal, A the alkaline earth metal, and M the transition metal). Structural and atomic parameters were also obtained for La0.94Ru3B2 compound from Rietveld refinement (CeCo3B2-type structure, P6/mmm space group (no. 191), a=5.5835(9) Å, c=3.0278(6) Å). 相似文献
5.
A new ternary compound, U3Co2Ge7, has been synthesized from the corresponding elements by a high temperature reaction using molten tin flux. It crystallizes in the orthorhombic La3Co2Sn7-type (Pearson's symbol oC24, space group Cmmm, No. 65) with lattice parameters determined from single-crystal X-ray diffraction as follows: a=4.145(2) Å; b=24.920(7); c=4.136(2) Å, V=427.2(3) Å3. Structure refinements confirm an ordered structure having two crystallographically inequivalent uranium atoms, occupying sites with dissimilar coordination. U3Co2Ge7 orders ferromagnetically below 40 K and undergoes a consecutive magnetic transition at 20 K. These results have been obtained from temperature- and field-dependent magnetization, resistivity and heat-capacity measurements. The estimated Sommerfeld coefficient γ=87 mJ/mol-U K2 suggests U3Co2Ge7 to be a moderately heavy-fermion material. 相似文献
6.
Ashok K. Ganguli Shalabh Gupta Jing-Tae Zhao E. Alejandro Leon-Escamilla 《Journal of solid state chemistry》2005,178(10):2959-2972
A particular pathology of certain W5Si3-type A5B3 structures (I4/mcm) appears to arise because of unduly close approaches of the A1-type atoms on the cell faces at , 0, () that occur with the larger and more electropositive A and/or in the presence of smaller B atoms. A structure refinement of binary Ba4.81Pb3 indicates such a marginal stability in that the Ba atoms in the facial Ba0.81 chains exhibit an extreme displacement ellipsoid along . Although Ca5Sn3 and La5Ga3 binaries are unknown in this structure type, five stable ternary derivatives of these have been synthesized via substitution reactions and characterized by single crystal X-ray diffraction means: Ca4Sn3.223(4)Mg0.777, Ca4Sn3Cu1.30(4), Ca4.66(6)Sn3Zn0.704(4), La4.81(1)Ga1.38(2)Al1.62, and La4.762(5)Ga1.5(1)Zn1.5. Only the Ca-Sn-Zn phase exhibits lower symmetry, P4/mbm. The problematic A1 sites exhibit diverse changes in these, whereas the surrounding B2 tetrahedra are largely unaltered. The Ca-Sn results are, respectively: direct Mg/Sn substitution at the Ca1 site; mixed fractional distribution of the smaller Cu at two sites around the A1 position with an unresolved disorder; a pair of apparently independent modes, fractional Ca in the normal position and fractional Zn rectangles thereabout. The two La-Sn phases contain normal Ga,Al (Ga,Zn) tetrahedral chains with pairs of fractional disordered La atoms along , 0, z. Each can be rationalized in terms of a reasonable incommensurate structure. Electronic effects may also be operable. 相似文献
7.
Subsolidus phase equilibria and crystal chemistry were studied for the La2O3-MgO-TiO2 system and for the ternary sections LaMg1/2Ti1/2O3-CaTiO3-La2O3 and LaMg1/2Ti1/2O3-CaTiO3-La0.833Mg0.25Ti0.75O3 in the quaternary La2O3-CaO-MgO-TiO2 system. Dielectric properties (relative permittivity and temperature coefficient of resonant frequency, τf) were measured at 5-10 GHz and mapped onto the phase equilibria relations to reveal the compositions of temperature-stable (τf=0) compounds and mixtures. Phase equilibria relations were obtained by X-ray powder diffraction analysis of approximately 80 specimens prepared by solid-state reactions in air at ∼1450°C. Six ternary phases were found to form in the La2O3-MgO-TiO2 system, including the three previously reported compounds LaMg1/2Ti1/2O3, La5Mg0.5Ti3.5O15, and “La6MgTi4O18”; and the new phases La10MgTi9O34, La9Mg0.5Ti8.5O31, and a perovskite-type solid solution (1−x)LaMg1/2Ti1/2O3-xLa2/3TiO3 (0?x?0.5). The phase previously reported as “La6MgTi4O18” was found to form off-composition, apparently as a point compound, at La6Mg0.913Ti4.04O18. Indexed experimental X-ray powder diffraction patterns are given for LaMg1/2Ti1/2O3, La5Mg0.5Ti3.5O15, La6Mg0.913Ti4.04O18, La10MgTi9O34, and La9Mg0.5Ti8.5O31. LaMg1/2Ti1/2O3 exhibits a slightly distorted perovskite structure with ordered B-cations (P21/n; a=5.5608(2) Å, b=5.5749(3) Å, c=7.8610(5) Å, β=90.034(4)°). La5Mg0.5Ti3.5O15 (Pm1; a=5.5639(1), c=10.9928(5) Å) and La6Mg0.913Ti4.04O18 (R3m; a=5.5665(1), c=39.7354(9) Å) are n=5 and n=6 members, respectively, of the (111) perovskite-slab series AnBn−1O3n. The new phases La10MgTi9O34 (a=5.5411(2), b=31.3039(9), c=3.9167(1) Å) and La9Mg0.5Ti8.5O31 (a=5.5431(2), b=57.055(1), c=3.9123(1) Å) are n=5 and n=4.5 members, respectively, of the (110) perovskite-slab series AnBnO3n+2, which exhibit orthorhombic subcells; electron diffraction revealed monoclinic superlattices with doubled c-parameters for both compounds. Extensive perovskite-type solid solutions form in the ternary sections LaMg1/2Ti1/2O3-CaTiO3-La2O3 and LaMg1/2Ti1/2O3-CaTiO3-La0.833Mg0.25Ti0.75O3. The La2O3-MgO-TiO2 system contains two regions of temperature-stable (τf=0) compositions. The quaternary La2O3-CaO-MgO-TiO2 system contains an extensive single-phase perovskite-type volume through which passes a surface of temperature-stable compositions with permittivities projected to be in the 40-50 range. Traces of this surface occur as lines of τf=0 perovskite-type phases in the ternary sections LaMg1/2Ti1/2O3-CaTiO3-La2O3 and LaMg1/2Ti1/2O3-CaTiO3-La0.833Mg0.25Ti0.75O3. 相似文献
8.
A. Grytsiv D. KaczorowskiA. Leithe-Jasper P. RoglC. Godart M. PotelH. Noël 《Journal of solid state chemistry》2002,163(1):37-43
Single crystals of the novel ternary compounds EuZn2Si2 and EuZn2Ge2 were grown from pure gallium, indium, or zinc metal used as a flux solvent. Crystal properties were characterized using X-ray single-crystal analyses via Gandolfi and Weissenberg film techniques and by four-circle X-ray single-crystal diffractometry. The new compounds crystallize with ternary derivative structures of BaAl4, i.e., EuZn2Si2 with ThCr2Si2-type (a=0.42607(2) nm, c=1.03956(5) nm, I4/mmm, R1=0.038) and EuZn2Ge2 with CaBe2Ge2-type (a=0.43095(2) nm, c=1.07926(6) nm, P4/nmm, R1=0.067). XAS and magnetic measurements on EuZn2Si2 and EuZn2Ge2 revealed in both compounds the presence of Eu2+ ions carrying large magnetic moments, which order magnetically at low temperatures. The magnetic phase transition occurs at TN=16 and 7.5 K for the silicide and the germanide, respectively. In EuZn2Si2 there occurs a spin reorientation at 13 K and furthermore some canting of antiferromagnetically ordered moments below about 10 K. In EuZn2Ge2 a canted antiferromagnetic structure is formed just at TN. 相似文献
9.
The crystal chemistry and crystallography of the compounds SrR2CuO5 (Sr-121, R=lanthanides) were investigated using the powder X-ray Rietveld refinement technique. Among the 11 compositions studied, only R=Dy and Ho formed the stable SrR2CuO5 phase. SrR2CuO5 was found to be isostructural with the “green phase”, BaR2CuO5. The basic structure is orthorhombic with space group Pnma. The lattice parameters for SrDyCuO5 are a=12.08080(6) Å, b=5.60421(2) Å, c=7.12971(3) Å, V=482.705(4) Å3, and Z=8; and for the Ho analog are a=12.03727(12) Å, b=5.58947(7) Å, c=7.10169(7) Å, V=477.816(9) Å3, and Z=8. In the SrR2CuO5 structure, each R is surrounded by seven oxygen atoms, forming a monocapped trigonal prism (RO7). The isolated CuO5 group forms a distorted square pyramid. Consecutive layers of prisms are stacked in the b-direction. Bond valence calculations imply that residual strain is largely responsible for the narrow stability of the SrR2CuO5 phases with R=Dy and Ho only. X-ray powder reference diffraction patterns for SrDy2CuO5 and SrHo2CuO5 were determined. 相似文献
10.
Single crystals of Ln5Ru2O12 (Ln=Pr, Nd, Sm-Tb) were grown out of either NaOH or KOH fluxes in sealed silver tubes. The crystals of all the phases were observed to be twinned as confirmed by TEM studies. The series crystallize in the C2/m monoclinic system with lattice parameters, a=12.4049(4)-12.7621(6) Å, b=5.8414(2)-5.9488(3) Å, c=7.3489(2)-7.6424(4) Å, β=107.425(3)-107.432(2)° and Z=2. The crystal structure is isotypic with the defect/disorder model of Ln5Re2O12 (Ln = Y, Gd) and consists of one dimensional edge shared RuO6 octahedral chains separated by a two dimensional LnOx polyhedral framework. Magnetic measurements indicate paramagnetic and antiferromagnetic behavior for Ln=Nd, Sm-Gd and Ln=Tb, respectively. 相似文献
11.
Christian KranenbergDirk Johrendt Albrecht Mewis Rainer PöttgenGunter Kotzyba Henning TrillBernd D Mosel 《Journal of solid state chemistry》2002,167(1):107-112
Two new compounds were synthesized by heating mixtures of the elements at 975-1025 K and characterized by single-crystal X-ray methods. CaZn2Si2 (a=4.173(2) Å, c=10.576(5) Å) and EuZn2Ge2 (a=4.348(2) Å, c=10.589(9) Å) crystallize in the ThCr2Si2-type structure (space group I4/mmm; Z=2). Magnetic susceptibility measurements of EuZn2Ge2 show Curie-Weiss behavior with a magnetic moment of 7.85(5)μB/Eu and a paramagnetic Curie temperature of 10(1) K. EuZn2Ge2 orders antiferromagnetically at TN=10.0(5) K and undergoes a metamagnetic transition at a low critical field of about 0.3(2) T. The saturation magnetization at 2 K and 5.5 T is 6.60(5) μB/Eu. 151Eu Mössbauer spectroscopic experiments show one signal at 78 K at an isomer shift of −11.4(1) mm/s and a line width of 2.7(1) mm/s compatible with divalent europium. At 4.2 K full magnetic hyperfine field splitting with a field of 26.4(4) T is detected. The already known compounds CaM2Ge2 (M: Mn-Zn) also crystallize in the ThCr2Si2-type structure. Their MGe4 tetrahedra are strongly distorted with M=Ni and nearly undistorted with M=Mn or Zn. According to LMTO electronic band structure calculations, the distortion is driven by a charge transfer from M-Ge antibonding to bonding levels. 相似文献
12.
A. Grytsiv D. KaczorowskiA. Leithe-Jasper P. Rogl M. PotelH. Noël A.P. PikulT. Velikanova 《Journal of solid state chemistry》2002,165(1):178-181
Single crystals of Yb3Ge5, grown from pure gallium or indium metal flux and investigated by means of CCD four-circle diffractometry, were consistent with the Th3Pd5-type of structure, displaying full order of vacancies and germanium atoms. From magnetic susceptibility and electrical resistivity measurements, performed on single-crystalline specimens, Yb3Ge5 was found to be an intermediate valent systems. 相似文献
13.
Shane J Crerar 《Journal of solid state chemistry》2004,177(7):2523-2529
The isostructural ternary silicides M2Cr4Si5 (M=Ti, Zr, Hf) were prepared by arc-melting of the elemental components. The single-crystal structure of Zr2Cr4Si5 was determined by X-ray diffraction (Pearson symbol oI44, orthorhombic, space group Ibam, Z=4, a=7.6354(12) Å, b=16.125(3) Å, c=5.0008(8) Å). Zr2Cr4Si5 adopts the Nb2Cr4Si5-type structure, an ordered variant of the V6Si5-type structure. It consists of square antiprisms that have Zr and Cr atoms at the corners and Si atoms at the centers; they share opposite faces to form one-dimensional chains ∞1[Zr4/2Cr4/2Si] surrounded by additional Si atoms and extending along the c direction. In a new interpretation of the structure, additional Cr atoms occupy interstitial octahedral sites between these chains, clarifying the relation between this structure and that of Ta4SiTe4. The formation of short Si-Si bonds in Zr2Cr4Si5 is contrasted with the absence of Te-Te bonds in Ta4SiTe4. The compounds M2Cr4Si5 (M=Ti, Zr, Hf) exhibit metallic behavior and essentially temperature-independent paramagnetism. Bonding interactions were analyzed by band structure calculations, which confirm the importance of Si-Si bonding in these metal-rich compounds. 相似文献
14.
Robin T. MacalusoJ.L. Sarrao P.G. PagliusoN.O. Moreno R.G. GoodrichD.A. Browne Frank R. FronczekJulia Y. Chan 《Journal of solid state chemistry》2002,166(1):245-250
The compounds CeMIn5 (M=Co, Rh, Ir) have been shown to exhibit heavy fermion behavior. In order to better understand this effect and the nature of the observed superconductivity, we have synthesized and characterized the non-magnetic analogs, LaMIn5 (M=Co, Rh, Ir). The structures of LaCoIn5, LaRhIn5, and LaIrIn5 were determined by single-crystal X-ray diffraction. CeMIn5 and LaMIn5 compounds are isostructural and adopt a tetragonal structure with space group P4/mmm, Z=1. Lattice parameters are a=4.6399(4) and c=7.6151(6) Å for LaCoIn5, a=4.6768(3) and c=7.5988(7) Å for LaRhIn5, and a=4.6897(6) and c=7.5788(12) Å for LaIrIn5. We compare these experimental data with band structure computations and examine structural trends that affect the magnetic and transport properties of these compounds. 相似文献
15.
The preparation and physical characterization of non-stoichiometric Ru2Ge3+x (0≤x≤1) are reported for the first time. The defect TiSi2-type chimney-ladder structure is maintained for the full stoichiometry range. The resistivity of Ru2Ge3+x increases systematically with x from 300 mΩ cm, x=0 -3 Ω cm, x=1 at 300 K. The temperature dependence is consistent with a variable range-hopping mechanism for x≥0.6. The Seebeck coefficients of samples do not evolve simply with x. A low thermal conductivity (κ300 K=0.03 W/K cm) suggests that Ru2Ge3 has some of the properties of a phonon-glass-electron-crystal. The low value of the thermoelectric figure of merit ZT=3.2×10−3 (T=300 K) calculated for Ru2Ge3 is due primarily to a low conductivity. 相似文献
16.
Xiaole Weng Paul Boldrin Isaac Abrahams Suela Kellici 《Journal of solid state chemistry》2008,181(5):1123-1132
A new direct route for the “bottom up” syntheses of phases in the Lan+1NinO3n+1 series (n=1, 2, 3 and ∞) has been achieved via single-step heat treatments of nanosized co-crystallized precursors. The co-crystallized precursors were prepared using a continuous hydrothermal flow synthesis system that uses a superheated water flow at ca. 400 °C and 24.1 MPa to produce nanoparticulate slurries. Overall, a significant reduction in time and number of steps for the syntheses of La3Ni2O7 and La4Ni3O10 was achieved compared with more conventional synthesis methods, which typically require multiple homogenization and reheating steps over several days. 相似文献
17.
Takatsugu Masuda Cara L. Nygren Kunimitsu Uchinokura 《Journal of solid state chemistry》2003,176(1):175-179
The structure of Cu2Fe2Ge4O13, previously thought to be CuFeGe2O6, has been determined from single-crystal X-ray diffraction data to be monoclinic, P21/m, a=12.1050(6), b=8.5073(4), c=4.8736(2) Å, β=96.145(1)°, Z=2, with R1=0.0231 and wR2=0.0605. The unique structure has an oligomer of four germanate tetrahedra, cross-linked laterally by square-planar copper ions, joined end-to-end by a zigzag chain of edge-sharing iron oxide octahedra. Running along the a-direction the metal oxide chain consists of alternating Cu-Cu and Fe-Fe dimers. A hypothetical series of homologous structures (Cun−2Fe2GenO3n+1 with n=3,4,…,∞) with different length germanate oligomers is proposed, where as n increases, the infinite chain of the CuGeO3 is approached. In this context, Cu2Fe2Ge4O13 is viewed as being built from blocks of CuGeO3 and the Fe oxide chains. This material has significance to the study of low-dimensional mixed-spin systems. 相似文献
18.
A new complete solid solution of NASICON-type compounds between LiZr2(PO4)3 and La1/3Zr2(PO4)3 was evidenced with the general formula Li1−xLax/3Zr2(PO4)3 (0?x?1). These phases were synthesized by a complex polymerizable method and structurally characterized from Rietveld treatment of their X-ray and neutron powder diffraction data. This solid solution results from the substitution mechanism Li+→1/3La3++2/3□ leading to an increase of the vacancies number correlated to an increase of the La content. According to this substitution mechanism, the general formula can then be written Li1−xLax/3□2x/3Zr2(PO4)3 (0?x?1) in order to underline the correlation between the La content and the vacancies rate. For all the compounds, the structure is clearly related to that of the NASICON family with three crystallographic domains evidenced. For 0?x?0.5, all the members adopt at high temperature the typical NASICON-type structure (s.g. R3¯c), while at lower temperature, their structure distorts to a triclinic form (s.g. C 1¯), as observed for LiZr2(PO4)3 prepared above 1100 °C. Moreover, in this domain, the reversible transition is clearly soft and the transition temperature strongly depends of the x value. For 0.6?x?0.9, the compounds crystallize in a rhombohedral cell (s.g. R3¯), while for x=1, the phase La1/3Zr2(PO4)3 is obtained (s.g. P3¯, Z=6, a=8.7378(2) Å, c=23.2156(7) Å).This paper is devoted to the structure analysis of the series Li1−xLax/3Zr2(PO4)3 (0?x?1), from X-ray and neutron powder thermo diffraction and transmission electron microscopy (TEM) studies. 相似文献
19.
Jérome Roger Volodymyr Babizhetskyy Joseph Bauer Roland Guérin Xavier Rocquefelte Jean-Yves Saillard 《Journal of solid state chemistry》2006,179(8):2310-2328
A series of binary rare-earth metal silicides RE5Si3 and ternary boron-interstitial phases RE5Si3Bx (RE=Gd, Dy, Ho, Lu, and Y) adopting the Mn5Si3-type structure, have been prepared from the elemental components by arc melting. Boron “stuffed” phases were subsequently heated at 1750 K within a high-frequency furnace. Crystal structures were determined for both binary and ternary series of compounds from single-crystal X-ray data: hexagonal symmetry, space group P63/mcm, Z=2. Boron insertion in the host binary silicides results in a very small decrease of the unit cell parameters with respect to those of the binaries. According to X-ray data, partial or nearly full boron occupancy of the interstitial octahedral sites in the range 0.6-1 is found. The magnetic properties of these compounds were characterized by the onset of magnetic ordering below 100 K. Boron insertion induces a modification of the transition temperature and θp values in most of the antiferromagnetic binary silicides, with the exception of the ternary phase Er5Si3Bx which was found to undergo a ferromagnetic transition at 14 K. The electrical resistivities for all binary silicides and ternary boron-interstitial phases resemble the temperature dependence of metals, with characteristic changes of slope in the resistivity curves due to the reduced electron scattering in the magnetically ordered states. Zintl-Klemm concept would predict a limiting composition RE5Si3B0.6 for a valence compound and should then preclude the stoichiometric formula RE5Si3B. Density functional theory calculations carried out on some RE5Si3Zx systems for different interstitial heteroatoms Z and different x contents from 0 to 1 give some support to this statement. 相似文献
20.
V Meignen A Lafond Y Moëlo C Guillot-Deudon A Meerschaut 《Journal of solid state chemistry》2004,177(8):2810-2817
Two new compounds, La5Ti2MS5O7 (M=Cu, Ag) were synthesized and their structures solved from single crystal X-ray data. Both compounds are isotypic. They crystallize in the orthorhombic system (space group Pnma, Z=4) with lattice constants a=19.423(1) Å, b=3.9793(2) Å, c=18.1191(9) Å for La5Ti2CuS5O7, and a=19.593(2) Å, b=3.9963(1) Å, and c=18.2973(15) Å for La5Ti2AgS5O7. The structure of these compounds is built from fragments of the rock-salt, perovskite and fluorite types and a clear anionic segregation of the anions appears in the structure. La5Ti2CuS5O7 and La5Ti2AgS5O7 exhibit an orange-yellow color and measurement of their optical band gap gave 2.02 and 2.17 eV, respectively. 相似文献