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.     

Un nouveau compose contenant des chaines lineaires unidirectionnelles d'atomes metalliques: PtBi1,6Pb0,4O3,8-4

A new ternary oxide, Pt(Bi_1.6Pb_0.4)O_3.8-4 has been isolated by reaction of Pt on Bi₂O₃, PbO mixtures. The unit cell is tetragonal: a = 8.765(2), $\text{c}\text{= 5.650(1)}\text{A}\text{?}$, Z = 4, space group P $\text{4}\text{ncc}$. The crystal structure has been refined by means of conventional Fourier and least-squares methods, to R = 0.036 (based on 356 independent reflections collected on an automated diffractometer). Pt (Bi_1.6Pb_0.4)O_3.8-4 is isostructural with CuBi₂O₄. Chains of square planar PtO₄ groups extend along c axis. Pt-Pt distance within the chain (2.82 Å) provides evidence of a strong metal-metal interaction as in partially oxidized compounds like KCP(Br). Interchain connections arise via (Bi,Pb)-O bonds.     

Zur kristallstruktur von (NH4)3Ti(O2)F5

The disordered ligand positions in (NH₄)₃Ti(O₂)F₅ (cubic, space group Fm3m - O⁵_h'$\text{a}\text{= 9.23}{}_2\text{A}\text{?}$) has been studied by X-ray single crystal investigation. A 3-dimensional fourier synthesis indicates a distribution of the disordered O-Atoms on the 96j positions (Oyz) similar to (NH₄)₃ZrF₇ where a pentagonal bipyramide has been proposed for geometrie of the ZrF₇-group. Due to the short O-O distance the structure of (NH₄)₃Ti(O₂)F₅ is better described as elpasolite where one of the six octahedral ligand positions are statistically replaced by an ‘edge on’ O^2?₂-group oriented there in two possible directions.     

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).     

Preparation and structural characterization of lead thiophosphate Pb3(PS4)2

Single crystals of cubic Pb₃(PS₄)₂ were grown by chemical vapour transport. Cell parameter $\text{a}\text{= 10.9393(7)}\text{A}\text{?}$; space group P2₁3. The structure was determined from 445 independent reflections and refined to R=5.0%. It consists of isolated PS₄ tetrahedra and an irregular eightfold sulphur coordination of lead. Second harmonic generation and optical activity were detected.     

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.     

The crystal structure of a new high -Nd- concentration laser material: Na3Nd(PO4)2

The crystal structure of Na₃Nd(PO₄)₂ has been determined from three-dimensional Mo-Kα diffractometer data. The space group is Pbc2₁, the lattice constants are: $\text{a}\text{= 15.874(8)}\text{A}\text{?}$$\text{b}\text{= 13.952(8)}\text{A}\text{?}$$\text{c}\text{= 18.470(9)}\text{A}\text{?}$ and there are 24 formula units per unit cell, giving a Nd concentration of 5.8 10²¹cm^?3. The final R-factor with 2329 independent reflections is 0.060. The structure of Na₃Nd(PO₄)₂, very closely related to that of Na₃La(VO₄)₂, is made up of isolated PO₄ tetrahedra and of sodium and neodymium atoms arranged in an ordered way. The tripling of the a parameter results only from the distortion of the PO₄ tetrahedra. The NdO_y polyhedra are isolated from one another and the shortest Nd-Nd distance is 4.65 Å.     

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.     

KTi6Nb5O25 : A member of a series of chemically twinned rutile oxides (AM3O9) (M2O4)n

A new oxide KTi₆Nb₅O₂₅ with a structure related to that of KTi₂Ta₅O₁₅ (1) has been prepared and described. It crystallizes in the orthorhombic system with unit-cell dimensions $\text{a}\text{= 6.611(4)}\text{A}\text{?}$, $\text{b}\text{= 8.880(8)}\text{A}\text{?}$, $\text{c}\text{= 30.154(18)}\text{A}\text{?}$ and space group Cmcm. The tunnel structure of this oxide has been studied from powder data. It is built up from rutile slabs whose width is determined by strings of six octahedra. This compound may be described as the fourth member of a chemically twinned rutile series (AM₃O₉) (M₂O₄)_n, KTi₂Ta₅O₁₇ being the second member of the series.     

Fluorite related ordered compounds in the ZrO2CaO and ZrO2Y2O3 systems

ZrO₂:CaO and ZrO₂:Y₂O₃ systems have been examined for possible ordered compounds. Fluorite related ordered compounds CaZr₄O₉ and Zr₃Y₄O₁₂ have been successfully prepared and identified. While it is believed that the former is monoclinic with $\text{a}\text{= 17.813 ± 0.005}\text{A}\text{?}$, $\text{b}\text{= 14.612 ± .004}\text{A}\text{?}$, $\text{c}\text{= 12.065 ± .003}\text{A}\text{?}$ and β = 119.5 ± .02° and isostructural with CaHf₄O₉, the latter appears to be isostructural with M₇O₁₂ type of compounds with $\text{a}\text{= 9.723 ± .001}\text{A}\text{?}$ and $\text{c}\text{= 9.090 ± 0.002}\text{A}\text{?}$, which is formed commonly in compounds containing tri and tetravalent cations and is characterized by a chain oxygen vacancy along a 〈111〉 of the original fluorite. No other fluorite related ordered compound could be detected in these systems.     

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.     

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.     

The crystal structure of Pb8Bi2(PO4)6O2

Single crystals of Pb₈Bi₂(PO₄)₆O₂ were grown by the Czochralski technique, and the structure of this compound was determined. It was found to crystallize in Pnma orthorhombic symmetry with a = 13.313, b = 10.284 and $\text{c}\text{= 9.219}\text{A}\text{?}$. The structure was refined to an R value of 7%. Powder diffraction data are also reported.     

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.     

Phase investigations in the system PbSIn2S3 and the crystal structures of PbIn2S4 and Pb6In10S21

The system PbS-In₂S₃ was examined by differential thermal analysis (DTA), chemical vapour transport (CVT), and X-ray diffraction. Five new phases of compositions closely related to the 1:1 ratio were found and prepared as needle-shaped single-crystals; their crystal data are reported. The structures of PbIn₂S₄ (orthorhombic, Pnma, a=11.688(1), b=3.8528(1), $\text{c}\text{=13.763(1)}\text{A}\text{?}$, Z=4) and Pb₆In₁₀S₂₁ (monoclinic, C2/m, a=27.629(3), b=3.8630(5), $\text{c}\text{=15.705(2)}\text{A}\text{?}$, β=95.9°, Z=2 were solved from 808 resp. 3554 independent reflexions and refined to R=0.116 resp. 0.068. In both structures the In-S coordination polyhedra are distorted octahedra, the Pb-S polyhedra are distorted bicapped trigonal prisms.     

La structure cristalline de Ca4Fe9O17: Des feuillets “hexagonaux” d'octaedres FeO6 et de bipyramides FeO5 lies par des tetraedres FeO4

The new calcium ferrite Ca₄Fe₉O₁₇, belonging to the CaFe_2+nO_4+n family ($\text{n}\text{=}\text{1}\text{4}$), has not the same stacking process of “FeO” blocks in “CaFeO₄” blocks, as the others terms of the series.It crystallizes in the monoclinic system, space group C2 with the parameters: $\text{a}\text{= 10,441}\text{A}\text{?}$, $\text{b}\text{= 6,025}\text{A}\text{?}$, $\text{c}\text{= 11,384}\text{a}\text{?}$ and β = 98°80. Its structure is characterized by the presence of iron atoms in oxygen octahedra and trigonal based bipyramides stacking in hexagonal layers along $\text{c}$.These layers are linked by iron atoms on tetrahedral sites. Calcium atoms are hexagonaly located around each tetrahedron.     

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.     

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.     

High pressure synthesis of Gd3InO6, Tb3InO6 and Lu3InO6

Three new compounds, X₃InO₆ (X = Gd, Tb, Lu) were prepared at 1–4 GPa, ～1050°C. They are monoclinic, space group $\text{P}\text{2}{}_1\text{n}$ with $\text{a}\text{? 8.9}\text{A}\text{?}$, $\text{b}\text{? 9.8}\text{A}\text{?}$, $\text{c}\text{? 5.9}\text{A}\text{?}$, β ～ 95° and Z = 4.     

Crystal structure of K5NdLi2F10

A single-crystal x-ray diffraction analysis has been performed on K₅NdLi₂F₁₀ synthesized from a melt containing an excess of KF and LiF as a flux. The structure is orthorhombic with space group Pnma, Z = 4, and cell parameters a = 20.65, b = 7.779, $\text{c}\text{= 6.902}\text{A}\text{?}$. A full-matrix least squares refinement gave R = 0.08 for 1056 independent reflections. The basic structural features are sheets, perpendicular to the a-axis, formed by isolated NdF₈ dodecahedra and LiF₄ tetrahedra. The sheets are held together by the K⁺ ions. The compound K₅NdLi₂F₁₀ is the first reported fluoride in which the Nd polyhedra are isolated from each other. The shortest Nd-Nd distance is 6.72 Å, and the concentration of Nd³⁺ ions is 3.60 × 10²¹ cm^?3.