Etude cristallographique du systeme FeSSc2S3 preparations et structures de FeSc2S4 et Fe0.85Sc2.10S4

The crystal structures of FeSc₂S₄ and Fe_0.85Sc_2.10S₄ have been determined by three dimensional X-ray diffraction. The cubic cells, space group Fd3m, have lattice constants $\text{a}\text{= 10,501}\text{A}\text{?}$ for FeSc₂S₄ and $\text{a}\text{= 10,444}\text{A}\text{?}$ for Fe_0.85Sc_2.10S₄. Iron is divalent and scandium trivalent. FeSc₂S₄ is a direct spinel structure, Fe_0.85Sc_2.10S₄ is near a spinel structure. Only 0,5 iron atom is on every 8a position; 0,175 Fe and 1,05 Sc lie on octahedral 16d and 16c site.     

Crystal structure of cubic MnSc2S4 and Mn2.29Sc1.14S4

The crystal structure of MnSc₂S₄ ($\text{a}\text{= 10.613}\text{A}\text{?}$, space group Fd3m) and Mn_2.29Sc_1.14S₄ ($\text{a}\text{= 10.523}\text{A}\text{?}$, space groupe Fd3m) were determined by three dimensional X-Ray diffraction. MnSc₂S₄ is a normal spinel structure and the atomic distribution shows that Mn_2.29Sc_1.14S₄ structure is intermediate between the rocksalt (MnS) and the spinel (MnSc₂S₄) types. Similar behaviour of Mn and Fe atoms in MnSSc₂S₃ and FeSSc₂S₃ systems was observed.     

Macle et structure cristalline de Mn0,75Ga2,17S4

Twins of $\text{Mn}{}_{\mathrm{<mtext>1?</mtext><mtext>x</mtext>}}\text{Ga}{}_{\mathrm{<mtext>2+</mtext><mtext>2</mtext><mtext>3</mtext><mtext>x</mtext>}}\text{S}{}_4$ were used for crystal structure determination. Twinning is explained by a reticular pseudomerihedry. Axis, plane and obliquity of the twin have been determined. Cell dimensions are: $\text{a = b}\text{= 5.456(2)}\text{A}\text{?}$; $\text{c}\text{= 10.220(4)}\text{A}\text{?}$; α = β = γ = 90°; space group 14; Z = 2. The final R value is 0.059. The material is isostructural with CdGa₂S₄.     

Structure determination of (3D) P2NbS8

Tridimensional P₂NbS₈ crystallizes in P4?n2 tetragonal space group, with $\text{a}\text{= 12.0483(4)}\text{A}\text{?}$, $\text{c}\text{= 7.2070(5)}\text{A}\text{?}$, $\text{V}\text{= 1046.2(1)}\text{A}\text{?}{}^3$ and Z = 4. The structure was anisotropically refined down to R = 2.3% from 468 reflexions and 53 variables. It is built from [Nb₂S₁₂] biprismatic bicapped units (average $\text{d}{}_{\mathrm{Nb?S}}\text{= 2.571}\text{A}\text{?}$) made of S^?II and S^?II₂ anions (dianionic distance of 2.014(3) Å). The niobium atoms are found as isolated Nb^IV ? Nb^IV pairs ($\text{d}{}_{\mathrm{Nb?Nb}}\text{= 2.859(1)}\text{A}\text{?}$) in these niobium group otherwise linked to each other through (PS₄) tetrahedral units (average $\text{d}{}_{\mathrm{P?S}}\text{= 2.051}\text{A}\text{?}$) themselves constituting interbonded [P₄S₁₂] rings. The P₂NbS₈ three-dimensional network thus obtained is compared to the (2D) P₂NbS₈, layered phase already described.     

Magnetic and crystallographic properties of Fe1−x(Cu0.5In0.5)xCr2S4 spinels

Fe_1?x(Cu_0.5In_0.5)_xCr₂S₄ spinel powders with 0 ≤ x ≤ 1 were prepared. Their lattice constant (a_o) increases linearly with x from a_o = 0.9995 nm for x = 0 to 1.0065 nm for x = 1. Cu⁺, In³⁺, and Fe²⁺ ions occupy tetrahedral A sites of the spinel lattice and Cr³⁺ ions the octahedral B sites. Spinels with 0 ≤ x ≤ 0.82 are ferrimagnets with Curie temperatures decreasing from 171 K for x = 0 to 116 K for x = 0.82. Spinels with 0.82< x≤ 1 are antiferromagnets with Néel temperatures between 31 K and 36 K. The magnetic moment of Fe_0.18Cu_0.41In_0.41Cr₂S₄ spinels was determined by susceptibility measurements to be 5.85 $\text{μ}{}_{\mathrm{<mtext>B</mtext>}}\text{molecule}$, which is equal to the calculated spin-only magnetic moment.     

The sodium ytterbium orthophosphate Na3(1+x)Yb(2-x)(PO4)3

A new sodium ytterbium orthophosphate with general formula Na_3(1+x)Yb_(2-x)(PO₄)₃ (0.07 ? x ? 0.50) has been prepared and characterized. Its crystal structure has been determined from a single crystal for x = 0.50. The space group is R3?c, the lattice constants are : $\text{a}\text{= 9.12(1)}\text{A}\text{?}$, $\text{c}\text{= 21.81(6)}\text{A}\text{?}$. The structure of Na_4.50Yb_1.50(PO₄)₃ is related to that of NaZr₂(PO₄)₃. The PO₄ tetrahedra and the (Yb,Na)O₆ octahedra form a three-dimensional skeleton in which the remaining sodium atoms are inserted. This structural type is also found for the phases Na_4.50Ln_1.50(PO₄)₃ (Ln = Tm, Lu) and Na_4.50Ln_1.50(AsO₄)₃ (Ln = Er, Tm, Yb, Lu).     

TlxTi6Se8 and TlxNb6Se8, two phases with filled up Nb3Te4 type of structure showing pronounced cation disorder

The new ternary chalcogenides Tl_xTi₆Se₈ (x= 0.76) and Tl_xNb₆Se₈ (x= 0.70) crystallize with a partially filled up Nb₃Te₄-structure: space group $\text{P}\text{6}{}_3\text{m}$, z= 1 with

$\text{a= 9.882(1) c= 3.590(1)}\text{A}\text{?}\text{(Tl}{}_{0.76}\text{Ti}{}_6\text{Se}{}_8\text{)}$

$\text{a= 10.033(2) c= 3.475(1)}\text{A}\text{?}\text{(Tl}{}_{0.70}\text{TNb}{}_6\text{Se}{}_8\text{)}$

The crystal structures were determined from single crystal diffractometer data and refined to a conventional R-value of 0.077 and 0.055 respectively. The T1 atoms in the octahedral channels cannot be localized. In Tl_xTi₆Se₈ diffuse scattering indicates one-dimensional short range order. A model of the cation distribution in Tl_0.76Ti₆Se₈ is discussed.     

Systeme Ga2S3PbS diagramme de phase,etude cristallographique

Four intermediate phases are present ; PbGa₂S₄,orthorombic EuGa₂S₄-type (a = 20,44 ; b = 20,64 ; $\text{c}\text{= 12,09}\text{A}\text{?}$) ; Pb₂Ga₂S₅, orthorombic space group Pbca (a = 12,38 ; b = 11,90 ; $\text{c}\text{= 11,03}\text{A}\text{?}$) ; and two Ga₂S₃-rich solid solutions, one of the wurtzite type at temperatures above 1000°C, one of the distorded blende type below about 970°C. PbGa₂S₄ has a peritectic decomposition at 930°C, and Pb₂Ga₂S₅ at 900 ± 5°C. The eutectic is at 730°C for about n = 0,80 ($\text{n}\text{=}\text{Pb}\text{Pb+Ga}$ atomic). A glassy region is obtained by quenching the liquid phase and its extent depends on the quenching temperature (at 1000°C, between n = 0,25 and n = 0,50).     

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.     

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.     

Contribution a l'etude du polymorphisme de Ga2S3: Structure cristalline de Mn0,23Ga1,85S3

The Mn_0.23Ga_1.85S₃ phase belongs to the solid solution $\text{ф}{}_0$, stable at low temperature in the Ga₂S₃MnS system. It is hexagonal superstructure of the wurtzite, with the Ga₂S₃α′ type ($\text{a}\text{= 6.397}\text{A}\text{?}$; $\text{c}\text{= 18.027}\text{A}\text{?}$Z = 6; space groupe P6₁ or P6₅). Its crystal structure has been refined by the least squares method to a final R = 0.06 with 323 independant reflections. This structure is closely related to Ga₂S₃ α described by Hahn and Frank, and differs only by the partial occupation of the vacant metal site of Ga₂S₃ by Mn atoms in statistical disorder.     

Comments on the system Ag2SIn2S3

The high temperature polymorph of AgInS₂ has been found to be orthorhombic with $\text{a}\text{=7.001}$, $\text{b}\text{=8.278}$, $\text{c}\text{=6.698}\text{A}\text{?}$, space group probably Pna2₁ with a distorted wurtzite structure. The phase transition temperature was found to be 620 ± 10°C and the melting point 880 ± 10°C. A new cubic spinel type phase was found at the composition AgIn₅S₈ with $\text{a}\text{=10.827}\text{A}\text{?}$.     

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.     

Systeme Ga2S3CdS etude cristallographique - diagramme de phase

This system is studied by D.T.A., X-ray diffraction and specially by the Guinier-Lenné method. Six intermediate phases are described. For n = 0.33 ($\text{n}\text{=}\text{Cd}\text{Cd+Ga}$) a compound CdGa₂S₄ which has two forms : one, α, stable at every temperature of the solid state, is tetragonal CdGa₂S₄-type ; the other, β, obtained only by quenching from the liquid, is an orthorhombic superstructure of the wurtzite. CdGa₂S₄ melts incongruenthy at 930°C. From n = 0.05 through n = 0.12 a solid solution of wurtzite-type (T > 950°C). In the neighbouring of n = 0.10 a solid solution of the blende-type (806°C < T < 906°C). For n = 0.70 a compound of the wurtzite-type which congruenthy melts at 960°C. From n = 0.85 through CdS a solid solution of the wurtzite-type (800°C < T < 900°C). A phase diagram is proposed.     

Crystal structure of KSb2PO8

KSb₂PO₈ crystallizes in the monoclinic system, space group Co, with $\text{a}\text{= 12.306(4)}\text{A}\text{?}$, $\text{b}\text{= 7.086(2)}\text{A}\text{?}$, $\text{c}\text{= 15.037(5)}\text{A}\text{?}$, β = 95.82(3)°, Z = 8. The structure was determined from 2149 reflexions collected on a NONIUS CAD4 automatic diffractometer with MoK$\text{}\text{?}$ga radiation. The final R index and weighted R_w index are 0.019 and 0.025 respectively. The structure is built up from SbO₆ octahedra sharing corners or edges and PO₄ tetrahedra sharing corners with octahedra to form a three-dimensional network. The potassium atoms are situated in the interconnected channellike cavities.     

Etude de la structure cristallographique et magnetique de Cu2FeGeS4 et remarque sur la structure magnetique de Cu2MnSnS4

Single crystal X ray diffraction shows that synthetic briartite Cu₂FeGeS₄ belongs to space group I 4&#x0304; 2 m. Powder neutron diffraction allows the determination of the propagation vector $\text{k}$ and of some features of the magnetic structure. $\text{k}\text{= [}\text{1}\text{2}\text{O}\text{1}\text{2}\text{]}$ as in Cu₂MnSnS₄. The degeneracies of the magnetic structures compatible with observations are discussed.     

Une nouvelle structure ordonnee derivee de la fluorine : Pb3ZrF10

Pb₃ZrF₁₀ crystallizes with orthorhombic symmetry, space group : Cmcm and unit-cell parameters : $\text{a}\text{= 10,713(3)}\text{A}\text{?}$, $\text{b}\text{= 12,817(4)}\text{A}\text{?}$, $\text{c}\text{= 5,909(2)}\text{A}\text{?}$ (Z = 4). Its structure has been solved and refined to a conventional R = 0,041 for 350 independent reflexions. It can be described as an ordered intergrowth of (Pb₂F₄)_n fluorite like monodimensional units and (Pb₄Zr₂F₁₆)_n columnar clusters built of two isolated square antiprisms sharing faces with four [PbF₁₁] complex polyhedra.A structural mechanism based on the transformation of edgesharing fluorite cubes to isolated square antiprisms is proposed to explain the change from fluorite to the anion-excess fluorite like Pb₃ZrF₁₀ structure.Analogies with homologous structures are discussed.     

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.