The Gallides SrRh2Ga2, SrIr2Ga2, and Sr3Ir4Ga4

The gallides SrRh₂Ga₂, SrIr₂Ga₂, and Sr₃Rh₄Ga₄ were obtained from the elements by induction melting and subsequent annealing. They were investigated by powder and single‐crystal X‐ray diffraction: CaRh₂B₂ type, Fddd, a = 573.2(1), b = 1051.3(1), c = 1343.7(2) pm, wR₂ = 0.0218, 398 F² values, 15 variables for SrRh₂Ga₂; a = 576.0(1), b = 1045.5(1), c = 1350.6(3) pm for SrIr₂Ga₂, and Na₃Pt₄Ge₄ type, I$\bar{4}$ 3m, a = 777.4(2) pm, wR₂ = 0.0234, 190 F² values, 11 variables for Sr₃Ir₄Ga₄. The gallides SrRh₂Ga₂ and Sr₃Ir₄Ga₄ exhibit complex, covalently bonded three‐dimensional [Rh₂Ga₂] and [Ir₄Ga₄] networks with short Rh–Ga (241–246 pm) and Ir–Ga (243–259 pm) distances. The strontium atoms fill large cages within these networks. They are coordinated by 8 Rh + 10 Ga in SrRh₂Ga₂ and by 4 Ir + 8 Ga in Sr₃Ir₄Ga₄. The structure of SrRh₂Ga₂ is discussed along with the monoclinic distortion variants HoNi₂B₂ and BaPt₂Ga₂ on the basis of a group‐subgroup scheme.     

ChemInform Abstract: The Gallides SrRh2Ga2, SrIr2Ga2, and Sr3Ir4Ga4.

The title gallides are prepared from the elements by induction melting and subsequent annealing (Ta ampules, 800 mbar Ar, 873—1073 K, 4 d) and characterized by powder and single crystal XRD.     

La0.8Sr0.2Ga0.8Mg0.2O3与La0.8Sr0.2Ga0.8Mg0.15Co0.05O3电导的对比

采用固相合成法制备了La0.8Sr0.2Ga0.8Mg0.2O3(LSGM8282)和La0.8Sr0.2Ga0.8Mg0.15Co0.05O3 (LSGMC5), 利用四电极交流阻抗法和Hebb-Wagner 极化法对比研究了两种材料的总电导率和电子电导率. 实验结果表明, LSGM8282 的总电导率与氧分压无明显依赖关系, 而LSGMC5 的总电导率在高氧分压区随氧分压降低而增加,在中等氧分压区域基本保持不变. 在973-1173 K的温度范围内, LSGM8282的自由电子电导率以及电子空穴电导率的氧分压级数分别为-1/4和1/4.在1073-1173 K的温度范围内, LSGMC5的自由电子电导率以及电子空穴电导率的氧分压级数分别为-1/4和约为1/8, 表明LSGMC5的空穴产生机制可能与LSGM8282不同. LSGM8282 的氧离子电导率与氧分压无关, 而LSGMC5 的氧离子电导率在高氧分压区随氧分压的减小而增加.     

Semiconducting behavior of type-I Si clathrate K8Ga8Si38

A ternary type-I Si clathrate K(8)Ga(8)Si(38) has been revealed to be an indirect band gap semiconducting material with an energy gap (E(g)) of approximately 0.10 eV, which is much smaller than the calculated E(g) value that is 0.15 eV wider than E(g) of elemental Si with the diamond-type structure.     

Structure change induced by terminal sulfur in noncentrosymmetric La2Ga2GeS8 and Eu2Ga2GeS7 and nonlinear-optical responses in middle infrared

Two new noncentrosymmetric quaternary sulfides, La(2)Ga(2)GeS(8) (1) and Eu(2)Ga(2)GeS(7) (2), have been synthesized by high-temperature solid-state reactions. The structure change on going from 1 to 2 to the known Li(2)Ga(2)GeS(6) (3) nicely shows that the reduced cation charge-compensation requirement causes a decrease in the number of terminal S atoms per formula, which is a key to determining the connectivity of the GaS(4) and GeS(4) building units. Powder sample 2 exhibits a strong second-harmonic-generation (SHG) response of about 1.6 times the benchmark AgGaS(2) at 2.05 μm laser radiation, a non type I phase-matchable behavior, and a comparable transparency region. The SHG intensities of these compounds originate from the electronic transitions from S 3p states to La/Eu/Li-S, Ga-S, and Ge-S antibonding states according to Vienna ab initio simulation package studies.     

Sr2Ru7B8, ein Strontium-Rutheniumborid mit einer neuen,vom AlB2-Typ abgeleiteten Kanalstruktur

Sr₂Ru₇B₈, a Strontium Ruthenium Boride with a New Channel Structure Derived from the AlB₂-Type The strontium ruthenium boride Sr₂Ru₇B₈ was prepared by reaction of the elements at 1 100°C (tantalum crucible sealed in a steel tube, excess of Sr). It crystallizes tetragonally in the space group P4₂/m with the lattice constants a = 644.4(1) pm, c = 1015.6(1) pm and Z = 2. The structure was determined by means of X-ray single crystal methods (four-circle diffractometer, MoKα, R = 0.034, R_w = 0.028, 1059 symmetrically independent reflections with I > 2σ_I, 37 variable parameters). Sr₂Ru₇B₈ forms a new channel structure derivable from the AlB₂ type by substitutions and shifting operations. The channels contain zig-zag chains of strontium atoms. They are running in the [100] and in the [010] directions in alternating layers. The boron atoms are arranged in pairs and in plane, branched B₆ groups. The electrical resistivity is in the range from ? = 2.4 mΩ · cm (290 K) to ? = 0.8 mΩ · cm (4.2 K) (pressed and sintered rods, 4-probe DC method).     

7-Chlormethyl-8-hydroxychinolin

Ohne Zusammenfassung     

Hydrothermal synthesis and structure of the new three-dimensional fluorogallophosphate JGP-4 with a Ga/P ratio of 7/8

A new 3-D fluorogallophosphate Ga₇P₈O₃₂F₄(C₆H₂₀N₄)₂·3H₃O⁺·H₂O (denoted JGP-4) with a Ga/P ratio of 7/8 has been synthesized hydrothermally by using triethylenetetramine as the template. It crystallizes in the tetragonal, space group (no. 114), with a=15.461(2), b=15.461(2), c=9.3233(1) Å, V=2228.67(5) Å³ and Z=2. This is the first metal phosphate with a M/P ratio of 7/8. The 3-D anionic framework of JGP-4 is built up from the vertex linkage of the 1-D chains and Ga₅P₄ building units, forming a 3-D open-framework with 8-membered and four square 4-membered rings along the c-axis direction.     

Synthese und Kristallstruktur von Sr3Ga2O5Cl2 und Sr3Fe1.18Al0.82O5Cl2

Solid state reactions, by using a flux, lead to the new compounds Sr₃Ga₂O₅Cl₂ (A) and Sr₃Fe_1.18Al_0.82O₅Cl₂ (B). By means of single crystal X-Ray determinations a monoclinic symmetry (space group C ₂ ² -P2₁, (A):a=9.569 (2) Å; (B):a=9.550 (2) Å,Z=4) was found. Both compounds are not isotypic to Sr₃Fe₂O₅Cl₂ but crystallize like Ba₃Fe₂O₅Cl₂.

     

Structural and Vibrational Studies of Sr2[W(CN)8]·10H2O

The crystal structure of distrontium octacyanotungstate decahydrate, Sr₂[W(CN)₈] · 10H₂O, was solved using X‐ray single crystal diffraction. The tungsten atom lies on a two fold axis. Eight cyanide anions create tetragonal antiprismatic coordination sphere of tungsten atom. The two edge‐sharing tetragonal antiprisms of [Sr(NC)₃(OH₂)₅], create a dimer, [Sr₂(CN)₆(H₂O)₆(μ‐H₂O)₂], which lies on the inversion center. One symmetry independent water molecule is located in a void of 40 Å³. Vibrational (FT‐IR and FT‐Raman spectroscopic) behavior of main structural units is discussed. It was spectroscopically confirmed that the geometry of [W(CN)₈]^4– anion is slightly distorted from that corresponding to “free” anion. The number of observed bands is significantly lower than that expected for C₂ point group.     

Ca(2.5)Sr(0.5)GaMn2O8: diamagnetic Ga in control of the structural and electronic properties of a bilayered manganate

The temperature dependence of the crystal structure and electronic properties of brownmillerite-like Ca(2.5)Sr(0.5)GaMn(2)O(8) has been studied by neutron powder diffraction and muSR spectroscopy. The results show that short-range 2D magnetic order begins to develop within the perovskite-like bilayers of MnO(6) octahedra approximately 50 K above the 3D Néel temperature of approximately 150 K. The bilayers show a structural response to the onset of magnetism throughout this temperature range whereas the GaO(4) layers that separate the bilayers only respond below the 3D ordering temperature. XANES spectroscopy shows that the sample contains Mn(3+) and Mn(4+) cations in a 1:1 ratio, and the behavior in the region of the Néel transition is interpreted as a local charge ordering. Electron diffraction and high-resolution electron microscopy have been used to show that the local microstructure is more complex than the average structure revealed by neutron diffraction, and that microdomains exist in which the GaO(4) tetrahedra show different orientations. It is argued that the bonding requirements of diamagnetic gallium control the electronic behavior within the perovskite-like bilayers.