NaFe(TeO3)2

The hydro­thermally prepared title compound, sodium iron(III) bis­[trioxotellurate(IV)], is isotypic with its GaIII analogue and consists of corrugated layers with an overall composition of [FeTe2O6]− together with Na+ cations. The layers extend parallel to (001) and are made up of [Fe2O10] edge-shared octa­hedral dimers and TeO3 trigonal pyramids sharing vertices. The Na+ cations are located in the cavities of this arrangement and link adjacent [FeTe2O6]− layers via distorted [NaO8] polyhedra

Crystal structure of the thortveitite-related M phase, (MnxZn1-x)2V2O7 (0.75 < x < 0.913): a combined synchrotron powder and single-crystal X-ray study.

The determination of the crystal structure of the M phase, (MnxZn1-x)2V2O7 (0.75 < x < 0.913), in the pseudobinary Mn2V2O7-Zn2V2O7 system for x ≃ 0.8 shows that the previously published triclinic unit-cell parameters for this thortveitite-related phase do not describe a true lattice for this phase. Instead, single-crystal X-ray data and Rietveld refinement of synchrotron X-ray powder data show that the M phase has a different triclinic structure in the space group P-1 with Z = 2. As prior work has suggested, the crystal structure can be described as a distorted version of the thortveitite crystal structure of β-Mn2V2O7. A twofold superstructure in diffraction patterns of crystals of the M phase used for single-crystal X-ray diffraction work arises from twinning by reticular pseudomerohedry. This superstructure can be described as a commensurate modulation of a pseudo-monoclinic basis structure closely related to the crystal structure of β-Mn2V2O7. In comparison with the distortions introduced when β-Mn2V2O7 transforms at low temperature to α-Mn2V2O7, the distortions which give rise to the M phase from the β-Mn2V2O7 prototype are noticeably less pronounced.Funding for this research was provided by: Royal Society (joint international exchange programme award to Anjan Sil); British Council, New Delhi (UKIERI project No. SA07-0052 to Kevin Knowles, Anjan Sil)

K3Al2As3O12

Single crystals of K3Al2As3O12, tripotassium dialuminotriarsenate(V), were obtained unintentionally by the reaction of KAsO3 with a corundum crucible at 973 K. The asymmetric unit contains three K, two Al, three As and 12 O atoms. The structure of the title compound is isotypic with those of other K3 M′2 X 3O12 (M′ = Al, Ga; X = P, As) structures and is made up of a three-dimensional network of corner-sharing [AlO4] and [AsO4] tetra­hedra. The three K+ cations are located in channels running along the [100], [001], [101] and [10] directions, exhibiting different coordination numbers of 9, 8 and 6, respectively. All corresponding [KOx] polyhedra are considerably distorted

Pb3Te2O6Br2

Single crystals of the title compound, trilead(II) bis­[tellurate(IV)] dibromide, have been grown under hydro­thermal conditions. The structure is isotypic with that of the chloride analogue, Pb3Te2O6Cl2, and consists of three Pb, two Te, two Br and four O atoms in the asymmetric unit. Except for two of the O atoms, all atoms are located on mirror planes. The Pb3Te2O6Br2 structure can be described as being built up from ∞ 2[Pb3Te2O6]2+ layers extending parallel to (20) and Br− anions between the layers. Cohesion of the structure is accomplished through Pb—Br contacts of two of the three lead atoms, leading to highly asymmetric coordination polyhedra. The lone-pair electrons of both TeIV and PbII atoms are stereochemically active and point towards the anionic halide layers

Crystal Structure and Characterisation of Mercury(II) Dichromate(VI)

Dark-red single crystals of HgCr2O7 were grown by reacting HgO and CrO3 in excess at 200°C for four days. The crystal structure (space group P32, Z = 3, a = 7.2389(10), c = 9.461(2) A, 1363 structure factors, 57 parameters, R[F2>2σ(F2)] = 0.0369, wR(F2 all) = 0.0693) was determined from a crystal twinned by merohedry according to (110). It consists of nearly linear HgO2 units (${\bar {d}}$(Hg–O) = 2.02 A) and dichromate units that are linked into infinite chains ‘O3Cr–O–CrO3–Hg–O3Cr–O–CrO3’ running parallel to the c-axis. Six additional Hg–O contacts between 2.73 and 2.96 A stabilise the structural arrangement. The dichromate anion exhibits a staggered conformation with a bent Cr–O–Cr bridging angle of 140.7(6)°. Upon heating above 300°C, HgCr2O7 decomposes in a two-step mechanism to Cr2O3. The title compound was additionally characterised by vibrational spectroscopy.Centro de Química Inorgánic

Ammonium bis(salicylaldehyde thiosemicarbazonato)ferrate(III), a supramolecular material containing low-spin FeIII

The synthesis and crystal structure (100 K) of the title com­pound, ammonium bis­[salicyl­aldehyde thio­semi­car­ba­zon­ato(2−)-κ3O,N1,S]iron(III), NH4[Fe(C8H7N3OS)2], is reported. The asymmetric unit consists of an octa­hedral [FeIII(thsa)2]− fragment, where thsa2− is salicyl­aldehyde thio­semi­car­ba­zon­ate(2−), and an NH4+ cation. Each thsa2− ligand binds via the thiol­ate S, the imine N and the phenolate O donor atoms, resulting in an FeIIIS2N2O2 chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis and the N atoms in trans positions. The FeIII ion is in the low-spin state at 100 K. The crystal structure belongs to a category I order–disorder (OD) family. It is a polytype of a maximum degree of order (MDO). Fragments of the second MDO polytype lead to systematic twinning by pseudomerohedry

Anisotropic Physical Properties of the Kondo Semimetal CeCu1.11_{1.11}As2_2

The recently proposed novel materials class called Weyl-Kondo semimetal (WKSM) is a time reversal invariant but inversion symmetry broken Kondo semimetal in which Weyl nodes are pushed to the Fermi level by the Kondo interaction. Here we explore whether CeCu$_{1+x}$As$_2$ may be a new WKSM candidate. We report on its single-crystal growth, structure determination and physical properties investigation. Previously published studies on polycrystalline samples suggest that it is indeed a Kondo semimetal, which is confirmed by our investigations on single crystals. X-ray diffraction reveals that CeCu$_{1+x}$As$_2$ crystallizes in a tetragonal centrosymmetric structure, although the inversion symmetry could still be broken locally due to partially occupied Cu sites. Chemical analysis results in an average occupation $x$ = 0.11(1). The electrical resistivity increases logarithmically with decreasing temperature, and saturates below 10 K. A Kondo temperature $T_{\mathrm{K}}$ $\approx$ 4 K is extracted from entropy, estimated from the specific heat measurements. From Hall effect experiments, a charge carrier density of $8.8 \times 10^{20}$ cm$^{-3}$ is extracted, a value characteristic of a semimetal. The magnetization shows pronounced anisotropy, with no evidence of magnetic ordering down to 0.4 K. We thus classify CeCu$_{1.11}$As$_2$ as a tetragonal Kondo semimetal with anisotropic magnetic properties, with a possibly broken inversion symmetry, thus fulfilling the necessary conditions for a WKSM state.Comment: 6 pages, 4 figures, Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019

The dehydration of SrTeO3(H2O) - a topotactic reaction for preparation of the new metastable strontium oxotellurate(IV) phase e-SrTeO3

Microcrystalline single-phase strontium oxotellurate(IV) monohydrate, SrTeO3 (H2O), was obtained by microwave-assisted hydrothermal synthesis under alkaline conditions at 180 ◦C for 30 min. A temperature of 220 ◦C and longer reaction times led to single crystal growth of this material. The crystal structure of SrTeO3 (H2O) was determined from single crystal X-ray diffraction data: P21/c, Z = 4, a = 7.7669(5), b = 7.1739(4), c = 8.3311(5)A˚ , b = 107.210(1)◦, V = 443.42(5)A˚ 3 , 1403 structure factors, 63 parameters, R[F2&gt;2s(F2 )] = 0.0208, wR(F2 all) = 0.0516, S = 1.031. SrTeO3 (H2O) is isotypic with the homologous BaTeO3 (H2O) and is characterised by a layered assembly parallel to (100) of edge-sharing [SrO6 (H2O)] polyhedra capped on each side of the layer by trigonal-prismatic [TeO3 ] units. The cohesion of the structure is accomplished by moderate O–H ◊ ◊ ◊ O hydrogen bonding interactions between donor water molecules and acceptor O atoms of adjacent layers. In a topochemical reaction, SrTeO3 (H2O) condensates above 150 ◦C to the metastable phase e-SrTeO3 and transforms upon further heating to d-SrTeO3 . The crystal structure of e-SrTeO3 , the fifth known polymorph of this composition, was determined from combined electron microscopy and laboratory X-ray powder diffraction studies: P21/c, Z = 4, a = 6.7759(1), b = 7.2188(1), c = 8.6773(2)A˚ , b = 126.4980(7)◦, V = 341.20(18)A˚ 3 , RFobs = 0.0166, RBobs = 0.0318, Rwp = 0.0733, Goof = 1.38. The structure of e-SrTeO3 shows the same basic set-up as SrTeO3 (H2O), but the layered arrangement of the hydrous phase transforms into a framework structure after elimination of water. The structural studies of SrTeO3 (H2O) and e-SrTeO3 are complemented by thermal analysis and vibrational spectroscopic measurements.Centro de Química Inorgánic

Synthesis, characterization and crystal structures of novel alkaline earth oxotellurates

Zsfassung in dt. SpracheErdalkalioxotellurate besitzen interessante kristallchemische und physikalische Eigenschaften.da nur spärliche Information über ihre Strukturchemie wurde der Schwerpunkt dieser Arbeit auf die Synthese und strukturelle Charakterisierung von Phasen im System M/Te/O/X (M=Mg, Ca, Sr, Ba; X=Cl, Br, OH, NO3) gelegt.Die Tellurate(IV) alpha-, beta-, beta'- und gamma-CaTeO3 wurden synthetisiert und mittels Röntgenbeugung (XRD) charakterisiert.Die Tieftemperaturphase alpha-CaTeO3 unterscheidet sich strukturell grundlegend von den Hochtemperaturphasen, die eng miteinander verwandt sind.gamma-CaTeO3 kann als OD-Struktur, bestehend aus zwei Arten apolarer Schichten beschrieben werden.gamma-CaTeO3 bestehen aus zwei Polytypen mit maximalem Ordnungsgrad (MDO).beta-CaTeO3 besitzt einen Phasenübergang bei ~293 K.Die Hoch- und Tieftemperaturmodifikationen (beta and beta') können als dreifache Überstruktur, basierend auf dem MDO$_1$ Polytyp von $\gamma$-CaTeO$_3$, angesehen werden.Einkristalle und einphasige mikrokristalline Proben von festen Lösungen mit Zusammensetzung Ca$_x$\-Sr$_{1-x}$\-TeO$_3$ wurden synthetisiert und mittels XRD charakterisiert.Abhängig vom eingesetzten Ca:Sr Verhältnis kristallisiert Ca(x)Sr(1-x)TeO3 im alpha-CaTeO3, gamma-CaTeO3 (MDO1 and MDO2), gamma-CaTeO3 (MDO1), beta''-CaTeO3 oder beta-SrTeO3 Strukturtyp.Drei verschiedene Kristallstrukturen wurden im System Ca(x)Sr(1-x)Te2O5 durch XRD aufgeklärt.Es handelt sich um acht-, zehn- und 28-fache Überstrukturen, deren Basisstrukturen der gleichen hexagonalen OD-Familie angehören.Bei systematische Untersuchungen der Bildungsbedingungen von Telluraten(IV) unter hydrothermalen Bedingungen wurden zahlreiche neue Verbindungen im System M/Te(IV)/O/X (M=K, Ca, Sr, Ba; X=Cl, Br, NO3, H2O, OH) erhalten.Die eng verwandten Strukturen von Sr4Te4O11Br2 and Sr4Te4O11(NO3)2 können mittels einer erweiterten OD-Theorie als bestehend aus Stäben und als vierfache Überstrukturen beschrieben werden.Ca3Te3O8Cl2.H2O besitzt ein verwandtes Ca/Te/O-Netzwerk, welches allerdings verzerrt ist, und wurde daher als OD-Struktur bestehend aus zwei Arten von Schichten beschrieben.Ca10Te8O23Cl6 ist eine OD-Struktur bestehend aus Schichten.Ca5Te4O12(NO3)2.2H2O ist a nicht-OD polytype Struktur.Eine Phase im System K/Ca/Te/O/Cl wurde zu einer vorläufigen Zusammensetzung von KCa3Te5O12Cl3 verfeinert.Die zugrunde liegende Kristallstruktur kann als OD-Struktur bestehend aus drei Arten von Schichten beschrieben werden.Das strukturelle Hauptmotiv der Kristallstrukturen von Ca6Te5O15(NO3)2, Ba6Te10O25Br2 and Ba3Te3O8Br2 sind dreidimensionale Te/O/M-Netzwerke, die von Kanälen durchdrungen werden, in die die freien Elektronenpaare der Te(IV)-Atome hineinragen und in denen sich die Anionen befinden.Ba6Te10O25Br2 kristallisiert in einer vierfachen Überstruktur.Einkristalle von Verbindungen mit einer Zusammensetzung M3Te2O6X2.xH2O (M=Ca, Sr, Ba; X=Cl, Br, OH) wurden unter hydrothermalen Bedingungen und im Erdalkalihalogenidfluss gezüchtet.Die kubischen Strukturen bestehen aus homeotypen Te/O/M-Netzwerken und unterscheiden sich in der Lage und der Besetzung der Halogenidatome und der Wassermoleküle.Die Strukturen der Orthotellurate(VI) des Strontium und Barium wurden mittels XRD aufgeklört.Sr3TeO6 und Ba3TeO6 sind acht und 40-fache Überstrukturen, die als pseudo-kubische dichte Packung von [TeO6]-Oktaedern mit M-Atomen (M=Sr, Ba) in den Tetraeder- und Oktaederlücken.Sie sind Hettotypen des Doppelperowskitstrukturtyps.Kristalle der polytypen Te(VI)-Verbindung MgTeO8H8 wurden mittels Geldiffusion gezüchtet.Ihre Strukturen bestehen aus einer Art von kristallchemischen Schichten, die durch O-H...O Wasserstoffbrückenbindungen verbunden sind. Um eine OD-Beschreibung zu erhalten, wurde die Struktur in zwei Arten von Schichten zerlegt.Die gemischtvalente Te(IV/VI)-Verbindung Tl2Te2O6 wurde in der Form von Einkristallen unter hydrothermalen Bedingungen und als einphasiges Pulver durch Festkörperreaktion hergestellt.Die Kristallstruktur ist Mitglied einer Kategorie IV OD Familie und eng mit der Struktur von Ag2Te2O6-III verwandt, die aus isotypen Te/O aber deutlich verschiedenen kationischen Schichten besteht.Oxotellurates(IV) and (VI) of alkaline earth metals bear interesting crystal-chemical and physico-chemical properties.Since the structural information on alkaline earth oxotellurates are scarce, the main focus of the present work was subjected to synthesis and structure determination of phases in the systems M/Te/O/X (M=Mg, Ca, Sr, Ba; X=Cl, Br, OH, NO3).The tellurates(IV) alpha-, beta-, beta'- and gamma-CaTeO3 were synthesized and characterized by X-ray diffraction (XRD), thermal analysis, and vibrational spectroscopy.The low-temperature phase alpha-CaTeO3 differs structurally from the metastable high-temperature phases which are closely related to each other.gamma-CaTeO3 can be described as an OD structure composed of two kinds of non-polar layers.The gamma-CaTeO3 crystals consist of two polytypes with a maximum degree of order (MDO).beta-CaTeO3 shows a distinct reversible phase transition at ~293 K. The high and low-temperature modification (beta and beta') can be considered as threefold superstructures based on the MDO1 polytype of gamma-CaTeO3.Single crystals and microcrystalline materials of solid solutions with composition Ca(x)Sr(1-x)TeO3 have been synthesized and characterized by XRD.Depending on the employed Ca:Sr ratio, Ca(x)Sr(1-x)TeO3 crystallizes in the alpha-CaTeO3, gamma-CaTeO3 (MDO1 and MDO2), gamma-CaTeO3 (MDO1), beta''-CaTeO3 or beta-SrTeO3 structure types.Three unique crystal structures were identified in the system Ca(x)Sr(1-x)Te2O5 by single crystal XRD.They are eight-, ten-, and 28-fold superstructures with basic structures which belong to the same hexagonal OD family.Systematic investigations of the building conditions of tellurate(IV) compounds under hydrothermal conditions resulted in the elucidation of numerous crystal structures in the system M/Te(IV)/O/X (M=K, Ca, Sr, Ba; X=Cl, Br, NO3, H2O, OH).The closely related structures Sr4Te4O11Br2 and Sr4Te4O11(NO3)2 can be described according to an extended OD theory of rods and as fourfold superstructures.Ca3Te3O8Cl2.H2O contains a related Ca/Te/O network, yet is, due to distortion, more favourably described as an OD structure composed of layers.Ca10Te8O23Cl6 is an OD structure composed of layers.Ca5Te4O12(NO3)2.2H2O is a non-OD polytypic structure.A phase in the system K/Ca/Te/O/Cl has been refined to a preliminary composition of KCa3Te5O12Cl3.The underlying crystal structure can be described as being composed of OD-layers and as a twelvefold superstructure.The main structural motifs of the crystal structures of Ca6Te5O15(NO3)2, Ba6Te10O25Br2 and Ba3Te3O8Br2 are three-dimensional Te/O/M networks which are perforated by channels in which the electron lone pairs of the Te(IV) atoms protrude and the anions are located.Ba6Te10O25Br2 crystallizes in a fourfold superstructure.Single crystals of phases with general formula M3Te2O6X2.xH2O (M=Ca, Sr, Ba; X=Cl, Br, OH) were grown under hydrothermal conditions and in alkaline earth halide fluxes.The cubic structures contain homeotypic Te/O/M networks and differ in the location and distribution of the anions and water molecules.The orthotellurates(VI) of strontium and barium were synthesized and their structures determined by XRD. Sr3TeO6 and Ba3TeO6 are eight- and 40-fold superstructures which can be described as a pseudo-cubic close-packing of [TeO6] octahedra with M (M=Sr, Ba) atoms located in the tetrahedral and octahedral voids. They are hettotypes of the cubic double perovskite structure type.Crystals of the polytypic Te(VI) compound MgTeO8H8 were grown using gel diffusion techniques.Their structures are composed of crystallochemical layers of one kind which are connected by O-H...O hydrogen bonds. To obtain an OD description, the structure was decomposed into layers of two kinds.The mixed valent Te(IV/VI) compound Tl2Te2O6 was obtained in the form of single crystals under hydrothermal conditions and as microcrystalline material by solid state reaction.The crystal structure belongs to a category IV OD family and is closely related to the structure of Ag2Te2O6-III which is composed of isotypic Te/O, but unrelated cationic layers.25