De nouveaux stannures ternaires de rhodium et d'elements des terres rares : TR2Rh3Sn5 OU TR = Y,Gd, Tb,Dy, Ho. structure cristalline et proprietes electriques et magnetiques de Y2Rh3Sn5

New ternary stannides are reported : RE₂Rh₃Sn₅ (RE = Y, Gd, Tb, Dy, Ho). Y₂Rh₃Sn₅ has been studied by single - crystal X-ray diffraction analysis. Its structure is of a new type with space group Cmc2₁ and Z = 4 : a = 4,387(2), b = 26,212(4), $\text{c}\text{= 7,1550(8)}\text{A}\text{?}$, D_x = 8,71 Mgm^?3, μ(AgK_α) = 17 mm^?1, F(000) = 1851, R = 0,045 for 478 independant reflexions (R_w = 0,046). This structure is characterized by a tridimensionnal lattice of RhSn covalent bonds with two very different sites for yttrium. Y₂Rh₃Sn₅ is diamagnetic and semimetallic according to its electrical properties.     

De nouveaux stannures ternaires de rhodium et d'elements des terres rares: TR1+xRh2Sn4−x, 0 ⩽ x ⩽ 0,5, TR = La - SmNew ternary stannides: TR1+xRh2Sn4−x, 0≦x≦0.5, TR = La - Sm

New ternary stannides are reported: RE_1+xRh₂Sn_4?x, 0 ? x ? 0,5 (RE = La ? Sm). NdRh₂Sn₄ has been characterized by single - crystal X-ray diffraction analysis. Its structure is of a new type with space group Pnma and Z = 4: a = 18,535(3), b = 4,463(1), $\text{c}\text{= 7,229(1)}\text{A}\text{?}$, D_x = 9,16 g.cm^?1, μ(AgKα) = 13,6 mm^?1, F(000) = 1300, R = 0,040 for 496 independent reflexions (R_w = 0,047). One of the tin sites can be partly occupied by rare earths atoms. The structure types of NdRh₂Sn₄ and Y₂Rh₃Sn₅ are closely related. LaRh₂Sn₄ does not exhibit superconductivity above 1.4 K.     

Oligoselenidogermanate (III): Zur kenntnis von Na6Ge2Se6 und Na8Ge4Se10

The following new oligomeric selenidogermanates (III) have been prepared and structurally characterized: Na₆Ge₂Se₆: monoclinic, space group $\text{P}\text{2}{}_1\text{c}$ (No. 14) a = 836.7(5) pm, b = 1192.4(8) pm, c = 815.8(5) pmβ = 118.63(15)°.The compound is isotypic to K₆Sn₂Te₆, essential structure elements are [Ge₂Se₆]^6? anions.Na₈Ge₄Se₁₀: triclinic, space group P1? (No. 2) a = 707.4(5) pm, b = 809.8(5) pm, c = 1065.7(6) pmα = 73.44(15)°, β = 70.84(15)°, ?= 81.73(15)°Two Ge₂Se₆ octahedra are connected by a common edge forming a six-membered cyclic [(GeSe₂)₄Se₂]^8? anion.     

Etude d'un nouveau germaniure ternaire : Pd∼12Mn∼4Ge8, de structure apparentee aux types Fe2P,Co2P ET Fe2As

The structural properties of a new ternary germanide of manganese and palladium Pd_～12Mn_～4Ge₈ have been investigated. The crystal structure has been determined by single-crystal X-ray diffraction analysis : R = 0.084 for 1027 independent reflexions. The structure is of a new type with one formula unit in an orthorhombic unit cell of space group Pnma, having the dimensions : $\text{a}\text{= 6.910 (1)}\text{A}\text{?}$, $\text{b}\text{= 3.146 (1)}\text{A}\text{?}$, $\text{c}\text{= 16.504 (4)}\text{A}\text{?}$. It is closely related to the Fe₂P, Co₂P and Fe₂As type structures. Pd_～12Mn_～4Ge₈ is ferromagnetic.     

Structure cristalline de Mn0, 4Er4, 6S7

The crystal structure of Mn₀, ₄Er₄, ₆S₇ ($\text{a}\text{= 12,573 (4)}\text{A}\text{?}$, $\text{b}\text{= 11,390 (4)}\text{A}\text{?}$, $\text{c}\text{= 3,777 (4)}\text{A}\text{?}$, γ = 105,45°, space group B2/m, Z = 2) has been refined by a least square method to a final R = 0,045, with 1431 independant reflections. The octahedral positions are occupied either by Er and Mn atoms or by Er atoms only and the prismatic sites by Er atoms.     

LuMnGe2, un nouveau type structural apparente a ceux de TiMn(Fe)Si2, ZrMnSi2 et ZrFeSi2; ScMnGe2, un nouvel isotype de TiMn(Fe)Si2

LuMnGe₂ has been studied by single - crystal X-ray diffraction analysis. The structure is of a new type with space group Cmmm and Z = 12: a = 5.466(2), b = 18.519(7), $\text{c}\text{= 8.173(3)}\text{A}\text{?}$, D_x = 9.03 Mg m^?3, μ(AgKα) = 31 mm^?1, F(000) = 1919, R = 0.030 for 593 independant reflexions (R_w = 0.034). The LuMnGe₂ structure type had been predicted and completes a large structural family TT′Si(Ge)₂ where T = Nb, Ti, Zr, Hf, Sc, Lu and T′ = Cr, Mn, Re, Fe, Co, where ScMnGe₂ is another new member, isostructural with TiMn(Fe)Si₂     

Ionic conductivity of Li4GeO4, Li2GeO3 and Li2Ge7O15

The ionic conductivity of polycrystalline samples of three lithium germanates: Li₄GeO₄, Li₂GeO₃, and Li₂Ge₇O₁₅, has been determined using a c techniques and complex plane analysis. Conductivities at 400°C are 8.7 × 10^?5, 1.5 × 10^?5, and $\text{1.4 × 10}{}^{\mathrm{?7}}\text{(Ω·}\text{cm}\text{)}{}^{\mathrm{?1}}$ respectively. The conductivity of Li₄GeO₄ rises appreciably in the range 700–750°C.     

Structure cristalline de l'orthophosphate monoacide de cuivre monohydrate CuHPO4,H2O

Monophosphate hydrogen copper monohydrate : CuHPO₄,H₂O is monoclinic, space group $\text{P}\text{2}{}_1\text{a}$. The unit cell parameters are : a = 8.63(6), b = 6.35(3), $\text{c}\text{= 6.82(5)}\text{A}\text{?}$, β = 94.14(6°) and Z = 4. The crystal structure has been determined with 1249 independent reflexions and refined to a final R value of 2.9%. The crystal is built up of PO₄ tetrahedron and CuO₆ octahedron deformed by Jahn-Teller effect which are linked to form a three dimensional network.Based on the inter-ionic distances between Cu^II and O^2? in the recently determined structures of monoarsenates or phosphates, we give a value for the effective ionic radius of copper II.     

Structure cristalline du seleniure d'Etain IV et de thallium I : Tl2SnSe3

The cell is orthorhombic, a = 8.051(3); b = 8.169(3); $\text{c}\text{= 21,24(1)}\text{A}\text{?}$; Z = 8; space groupe Pnam, d_calc = 7.2; d_obs = 7.1; μ = 897 cm^?1. R = 0.065 for 1636 reflections.The anion Sn₂Se^4?₃ is formed by two SnSe₄ tetrahedra, which have a common edge. Two kinds of thallium atoms are observed, with different coordinations.     

Polymorphisme sous pression de Sm2Ge2O7 et identification de la nouvelle phase H de la serie des digermanates de terres rares

The pressure-temperature phase diagram of Sm₂Ge₂O₇ was determined up to 80 kbar and 1400°C. In this pressure-temperature range only two phases were found. The B″ triclinic phase synthetised at atmospheric pressure is stable up to 40 kbar and at higher pressures appears the H phase which is a new type of structure in the rare earth digermanate series. The lattice parameters of the H phase were determined on small single crystals which were grown with water as mineralizer. The symmetry of the H phase is hexagonal with a space group P 6/m m m. The cell parameters of H-Sm₂Ge₂O₇ are $\text{a}\text{= 11,26}\text{A}\text{?}$ and $\text{c}\text{= 31,80}\text{A}\text{?}$. The measured density is 7,01 g/cm³ and therefore the cell contains twenty seven Sm₂Ge₂O₇ units. The calculated density is 7,16 g/cm³. The X-ray diffraction pattern of H-Gd₂Ge₂O₇ previously obtained can be indexed with similar parameters $\text{a}\text{= 11,19}\text{A}\text{?}$ and $\text{c}\text{= 31,65}\text{A}\text{?}$.     

Crystal structure and magnetic properties of Cu4NiSi2S7

The structure of the compound Cu₄NiSi₂S₇ has been determined. It crystallizes in a new, monoclinic distorted sphalerite superlattice with the parameters: $\text{a}\text{= 11.551}\text{A}\text{?}$, $\text{b}\text{= 5.313}\text{A}\text{?}$, $\text{c}\text{= 8.165}\text{A}\text{?}$, β = 98.72°, $\text{V}\text{= 495.2}\text{A}\text{?}{}^3$, Z = 2, space group C2. The analogous compound Cu₄NiGe₂S₇ is isotypic. At a Neél temperature T_N = 20.2 K, Cu₄NiSi₂S₇ becomes antiferromagnetic. The magnetic moment of the paramagnetic phase is 2.6μ_B.     

Structures cristallines des phases M2Ga2Fe2O9 (M = In,Sc) nouveaux exemples de coordinence 5 du fer

New quaternary oxides are reported : M₂Ga₂Fe₂O₉ (M = In,Sc). In₂Ga₂Fe₂O₉ has been studied by single-crystal X-ray diffraction analysis. Its structure is a new type with space group Pba2 and $\text{z}\text{=}\text{8}\text{3}\text{:}\text{a}\text{= 19.253(3)}$, b = 7.2176(2), $\text{c}\text{= 3.2581(1)}\text{A}\text{?}$, D_x = 6.05 g.cm^?3, μ(AgK_α) = 9mm^?1, F(000) = 757.1, R = 0.037 for 420 independant reflexions (R_w = 0.037). The indium are heptahedrally coordinated by seven oxygen atoms and the iron and gallium atoms by five oxygen atoms at the apices of a trigonal bipyramid.     

Preparation,stabilite et etude cristallographique preliminaire du compose Bi2Sn2O7

Our crystallochemistry investigation of the Bi₂O₃ - SnO₂ binary in the range of compositions between 60 and 75 SnO₂ moles percent, brings new evidence of the compound Bi₂Sn₂O₇. It has a tetragonal structure ($\text{a}\text{= 21.31}\text{A}\text{?}$, $\text{c}\text{= 21.53}\text{A}\text{?}$), related to the pyrochlore structure.From this study arises a new problem about the influence of Bi3+ ion on the doubling of the crystalline parameters.     

A series of rare earth silicates RE3+2M3+[SiO4]2 (OH)

A series of isotypic silicates of composition RE₂M[SiO₄]₂ (OH) with RE = La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, and M = Al³⁺, Fe³⁺ has been synthesized under hydrothermal conditions. Lattice constants of two members as determined from single crystal X-ray diffraction data are: La₂Al[SiO₄]₂ (OH) (La₂Fe[SiO₄]₂ (OH)) $\text{a}{}_{\mathrm{o}}\text{= 7.401 (7.346)}\text{A}\text{?}$, $\text{b}{}_{\mathrm{o}}\text{= 5.702 (5.862)}\text{A}\text{?}$, $\text{c}{}_{\mathrm{o}}\text{= 17.072 (97.196)}\text{A}\text{?}$, gb = 112.4 (112.5°), $\text{P}\text{2}{}_1\text{c}$, Z=4.     

New tetrahedrally coordinated A2CdBr4 compounds (A = Cs,CH3NH3)

(CH₃NH₃)₂CdBr₄ and Cs₂CdBr₄ are two compounds with a tetrahedral CdBr₄-coordination. Their room temperature structures are determined. (CH₃NH₃)₂CdBr₄: monoclinic, $\text{P}\text{2}{}_1\text{c}$, $\text{a}\text{= 8.1227(13)}\text{A}\text{?}$, $\text{b}\text{= 13.4355(16)}\text{A}\text{?}$, $\text{c}\text{= 11.4194(13)}\text{A}\text{?}$, β = 96.194(11) °, z = 4. Cs₂CdBr₄: orthorhombic, Pnma, $\text{a}\text{= 10.235(5)}\text{A}\text{?}$, $\text{b}\text{= 7.946(3)}\text{A}\text{?}$, $\text{c}\text{= 13.977(5)}\text{A}\text{?}$, z = 4.     

Hydrogen bonding in NH4HSO4. NH4H2PO4

NH₄HSO₄·NH₄H₂PO₄ is monoclinic $\text{P}\text{2}{}_1\text{n}$ with Z = 2 and the following unit cell dimensions : a = 7.723(5), b = 7.540(5), $\text{c}\text{= 7.482(5)}\text{A}\text{?}$, β = 101.32(5)°. Crystal structure of this salt has been solved with a final R value 0.028. As in the corresponding potassium salt PO₄ and SO₄ tetrahedra are randomly distributed.A complete hydrogen bonding pattern is given.     

Un nouveau sulfure de molybdene : Mo3S4 preparation,proprietes et structure cristalline

Un nouveau sulfure de molybdène : Mo₃S₄, isostructural de Mo₃Se₄, a été préparé. Sa maille cristallographique est rhomboédrique : a = 6, re A ; α = 91°34 ; Z = 2 ; groupe spatial R3?. Sa structure est caractérisée par un motif Mo₆S₈ constitué d'un cluster octaédrique Mo₆ ($\text{Mo}\text{}\text{Mo}\text{= 2, 69}\text{A}\text{?}$ et 2, 86 Å) inscrit dans un cube déformé de soufre.     

Mise en evidence de tetraedres PN4 dans le nitrure Mg2PN3 de type wurtzite

Mg₂PN₃ has been prepared by reaction in solid state between Mg₃N₂ and P₃N₅. It crystallizes with orthorhombic symmetry, space group Pna2₁, with unit cell parameters a = 9.759 (5), b = 5.635 (3), $\text{c}\text{= 4.743 (3)}\text{A}\text{?}\text{z}\text{= 4}$. Its structure is related to the wurtzite type with Mg and P atoms ordered. It is the first example of PN₄ tetrahedra in a normal tetrahedral structure.     

The many phases of HUP, (UO2)[HPO4] · 4H2O. An electron-optical investigation

The prompt recrystallization of the tetragonal phyllophosphate HUP, (UO₂)[HPO₄] · 4H₂O, when rinsed with distilled water at ambient temperature, has been studied by TEM, SEM and SAD. In course of the rinsing process, to remove excess phosphorous acid, HUP underwent an orthorhombic phase change, which produced two orthorhombic phases O₁ and O₂. O₁ has $\text{a = 7.6(3)}\text{A}\text{?}$, $\text{c = 7.0(4)}\text{A}\text{?}$, and 001 absent for l odd. O₂ has $\text{a = 7.3(2)}\text{A}\text{?}$, $\text{c = 6.8(2)}\text{A}\text{?}$ and no systematic absent reflections. O₁ and O₂ are metastable and by spinodal decomposition modulate into monoclinic phases through a string of intermediate and disordered phases with the β-angle increasing from 90.0° (orthorhombic phases) to 91.3(3)°, 95(2)° and 97.7(2)° for M_2.2, M_2.1, and M_1.1 respectively, where M_1.1 is the monoclinic derivative ($\text{a = 6.9(4)}\text{A}\text{?}$, $\text{c = 6.4(4)}\text{A}\text{?}$, β = 97.7(3)°) of O₁ and M_2.1 ($\text{a = 7.3(4)}\text{A}\text{?}$, $\text{c = 12.1(3)}\text{A}\text{?}$, β = 95(2)°) together with M_2.2 ($\text{a = 14.22(4)}\text{A}\text{?}$, $\text{c = 13.08(4)}\text{A}\text{?}$, β = 91.3(3)°) are the derivatives of O₂. The crystallographic b axis could not be determined. All the abovementioned phases exhibit a striking epitaxial relationship which presumably gives the clue to the fact that these phase findings are at variance with X-ray findings given in literature. It is suggested that the phases are isomeric polymorphs of HUP.     

High pressure synthesis of Cu2GeO4 with hausmannite structure

Copper(II)metagermanate, CuGeO₃, decomposes at high pressure to rutile-type GeO₂ and Cu₂GeO₄. Very small single crystals of Cu₂GeO₄ can be obtained by direct high pressure synthesis from CuOGeO₂ mixtures. The compound has a distorted spinel structure (Hausmannite structure, space group $\text{I}\text{4}{}_1\text{amd}$) with $\text{a}\text{= 5.593}\text{A}\text{?}$, $\text{c}\text{= 9.396}\text{A}\text{?}$, Z = 4.