Neuartige Polyanionen in Zintlphasen Zur Kenntnis von Na7Al2Sb5

New Types of Polyanions in Zintl Phases: On Na₇Al₂Sb₅ The new compound Na₇Al₂Sb₅ crystallizes in the monoclinic system, space group P2₁/m (Nr. 11) with the lattice constants AlSb₄-tetrahedra are connected by common corners, edges and Sb₂ groups to anionic sheets, between which the Na⁺ ions are located.     

Ga-Ga bonding and tunnel framework in the new Zintl phase Ba3Ga4Sb5

A new Zintl phase Ba₃Ga₄Sb₅ was obtained from the reaction of Ba and Sb in excess Ga flux at 1000°C, and its structure was determined with single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group Pnma (No. 62) with a=13.248(3) Å, b=4.5085(9) Å, c=24.374(5) Å and Z=4. Ba₃Ga₄Sb₅ has a three-dimensional [Ga₄Sb₅]⁶⁻ framework featuring large tunnels running along the b-axis and accommodating the Ba ions. The structure also has small tube-like tunnels of pentagonal and rhombic cross-sections. The structure contains ethane-like dimeric Sb₃Ga-GaSb₃ units and GaSb₄ tetrahedra that are connected to form 12- and 14-membered tunnels. Band structure calculations confirm that the material is a semiconductor and indicate that the structure is stabilized by strong Ga-Ga covalent bonding interactions.     

Zintlphasen mit isolierten SiAs4- bzw. GeAs4-Anionen: Darstellung und Struktur von Ba4SiAs4 und Ba4GeAs4 sowie Sr4SiAs4 und Sr4GeAs4

Die erstmals dargestellten isotypen Verbindungen Ba₄SiAs₄, Ba₄GeAs₄, Sr₄SiAs₄ und Sr₄GeAs₄ kristallisieren kubisch, Raumgruppe P4 3n, mit 8 Formeleinheiten in der Elementarzelle: In den Strukturen liegen isolierte, d.h. nur von Ba-Ionen umgebene SiAs - bzw. GeAs -Tetraeder vor. Die Verbindungen sind die bisher eindrucksvollsten Beispiele für Zintlphasen mit komplexen Anionen. Zintl Phases with Isolated SiAs₄ or GeAs₄ Anions: Preparation and Structure of Ba₄SiAs₄, Ba₄GeAs₄, Sr₄SiAs₄, and Sr₄GeAs₄ The new compounds Ba₄SiAs₄, Ba₄GeAs₄, Sr₄SiAs₄, and Sr₄GeAs₄ have been prepared and their structures determined. They crystallize in the cubic system, P4 3n, with axes: data see “Inhaltsübersicht”. There are isolated SiAs or GeAs tetrahedra in the structures. The compounds can be interpreted as Zintl phases with complex anions.     

Sb2Hg3GaBr4: A New Supramolecular Framework Structure with [Sb2Hg4/2]±0 Building Blocks Isosteric to Distibane

Sb₂Hg₃GaBr₄ is a new air stable transparent reddish solid that crystallizes in space group Pnma (No. 62, Z = 8) with the lattice constants a = 1375.49(8) pm, b = 1269.0(1) pm, c = 1478.19(9) pm. The title compound represents a new structure type based on a cationic framework of a significantly modified Millons base type. Structural building blocks of the cationic partial structure are well known tetrahedral [SbHg_4/2]⁺ groups and unprecedented formally neutral [Sb₂Hg_4/2]^±0 units in a 2:1 ratio. The [Sb₂Hg_4/2]^±0 units contain covalent Sb‐Sb bonds (d = 285.6 pm) and are isosteric with Distibane Sb₂H₄ in a staggered conformation. Structural consequences of the lone pairs located at the Sb atoms of the [Sb₂Hg_4/2]^±0 units are discussed. The charge of the cationic framework is balanced by disordered anions in suitable cavities. They appear as tetrahedral [GaBr₄]^? but correspond most likely to a superposition of bitetrahedral apex sharing [Ga₂Br₇]^? and isolated Br^?.     

Gallium substitutions as a means to stabilize alkaline-earth and rare-earth metal pnictides with the cubic Th3P4 type: Synthesis and structure of A7Ga2Sb6 (A=Sr, Ba, Eu)

Three new compounds—Sr_7.04(2)Ga_1.94(2)Sb₆, Ba_7.02(3)Ga_1.98(3)Sb₆ and Eu_7.04(3)Ga_1.90(3)Sb₆—have been synthesized from reactions of the corresponding elements using gallium as a metal flux. Their crystal structures (space group I4¯3d (No. 220), Z=2 with unit cell parameters: a=9.9147(9) Å for the Sr-compound; a=10.3190(9) Å for the Ba-compound; and a=9.7866(8) Å for the Eu-compound) have been established by single-crystal X-ray diffraction. The structures are best described as Ga-stabilized derivatives of the hypothetical Sr₄Sb₃, Ba₄Sb₃ and Eu₄Sb₃ phases with the cubic Th₃P₄ type. Such an inclusion of interstitial Ga atoms in this atomic arrangement results in the formation of isolated [Ga₂Sb₆]¹⁴⁻ fragments, isoelectronic and isostructural with the [Sn₂Te₆]⁶⁻ anions in the K₃SnTe₃ type, and allows for the attainment of a charge-balanced electron count. In that sense, the Sr₄Sb₃, Ba₄Sb₃ and Eu₄Sb₃ binaries, which are expected to be electron-deficient and are currently unknown, can be “turned” into Sr₇Ga₂Sb₆, Ba₇Ga₂Sb₆ and Eu₇Ga₂Sb₆, whose structures are readily rationalized following the Zintl concept.     

Eu7Ga6Sb8: A Zintl phase with Ga-Ga bonds and polymeric gallium antimonide chains

The Zintl phase Eu₇Ga₆Sb₈ was obtained from a direct element combination reaction at 900°C. It crystallizes in the orthorhombic space group Pbca (No. 61) with a=15.6470(17) Å, b=17.2876(19) Å, c=17.9200(19) Å, and Z=8. In Eu₇Ga₆Sb₈, the anionic framework forms infinite chains of [Ga₆Sb₈]¹⁴⁻ which are arranged side by side to make a sheet-like arrangement but without linking. The sheets of chains are separated by Eu²⁺ atoms and also within the sheet, Eu²⁺ atoms fill the spaces between two chains. The chain is made up of homoatomic tetramers (Ga₄)⁶⁺ and dimers (Ga₂)⁴⁺ connected by Sb atoms. The compound is a narrow band-gap semiconductor with E_g∼0.6 eV and satisfies the classical Zintl concept. Extended Hückel band structure calculations confirm that the material is a semiconductor and suggest that the structure is stabilized by strong Ga-Ga covalent bonding interactions. Magnetic susceptibility measurements for Eu₇Ga₆Sb₈ show that the Eu atoms are divalent and the compound has an antiferromagnetic transition at 9 K.     

Über hexagonale Perowskite mit Kationenfehlstellen. XXX. 5 L-Stapelvarianten in den Systemen BaO?Re2O7?Sb2O5 und BaO?WO3?Sb2O5

On Hexagonal Perovskites with Cationic Vacancies. XXX. 5 L Stacking Polytypes in the Systems BaO — Re₂O₇? Sb₂O₅ and BaO? WO₃? Sb₂O₅ In the systems BaO? Re₂O₇? Sb₂O₅ and BaO? WO₃? Sb₂O₅ phases of composition Ba₅BaRe Sb□O_15?x□_x (x = 0 up to x ? 3/4) and Ba₅BaWSb□O_15?x/2□_x/2 (x ? 3/2 up to x ? 2) are existent, which have an orthorhombic distorted 5 L structure. The pure Sb compound has to be formulated as Ba₃BaSb₂O₉ and crystallize in an orthorhombic variant of the hexagonal BaTiO₃ type.     

Ba5Ti12Sb19+x, a polar intermetallic compound with a stuffed γ-brass structure

The polar intermetallic compound Ba₅Ti₁₂Sb_19+x (x0.2) has been synthesized by reaction of the elements. Single-crystal X-ray diffraction analysis revealed that it adopts a new structure type (Ba₅Ti₁₂Sb_19.102(6), space group , Z=2, a=12.4223(11) Å, V=1916.9(3) Å³). The set of Ba and Sb sites corresponds to the structure of Cu₉Al₄, a γ-brass type with a primitive cell. A complex three-dimensional framework of Ti atoms, in the form of linked planar Ti₉ clusters, is stuffed within the γ-brass-type Ba–Sb substructure. Notwithstanding its relationship to the γ-brass structure, the compound does not appear to conform to the Hume–Rothery electron concentration rules. Band structure calculations on an idealized Ba₅Ti₁₂Sb₁₉ model suggest that the availability of bonding states above the Fermi level is responsible for the partial occupation, but only to a limited degree, of an additional Sb site within the structure. Magnetic measurements indicated Pauli paramagnetic behaviour.     

Ternäre Verbindungen des Natriums und Kaliums mit CaCu4P2-Struktur

Ternary Compounds of Sodium and Potassium with CaCu₄P₂-type Structure NaCu₄As₂, NaCu₄Sb₂, KCu₄As₂, and KCu₄Sb₂ were prepared and investigated by single crystal methods. They crystallize rhombohedrally and are isotypic to CaCu₄P₂ (space group R3 m). The (hexagonal) lattice constants are By reaction of the same element compositions but alterated conditions six further compounds could be synthesized in the systems Na(K)/Cu(Ag)/P(As, Sb). They crystallize hexagonally, their structure which has not been determined seems to be related to the structure of CaCu₄P₂.     

Die Kristallstruktur der Hexagonalen Verbindungen BaMeIISbO9. II. Ba3CuSb2O9

Crystal Structure of the Hexagonal Compounds Ba^II₃Me^IISb^v₂O₉. II. Ba₃CuSb₂O₉ The crystal structure of the compound Ba₃CuSb₂O₉ was determined from single crystal X-ray diffraction data and refined down to R = 0.03. Ba₃CuSb₂O₉ crystallizes in the hexagonal space group P6₃mc (C) with a = b = 5.809 Å, C = 14.321 Å and Z = 2. The structure can be described by close–packed BaO₃ layers in the sequence cchcchcch…?(hex. BaTiO₃ type). Groups of two octahedra with common faces are connected by SbO₆ octahedra via common corners. They are occupied alternately by Cu and Sb. In agreement with the EPR spectra the CuO₆-octahedra present no static Jahn-Teller distortion at room temperature. However the thermal ellipsoids of the oxygen atoms indicate the presence of adynamic Jahn-Teller-effect.     

RbSb2 – Eine mit KSb2 verwandte Zintl‐Phase

RbSb₂ – A Zintl Phase related to KSb₂ The electron‐precise Zintl compound RbSb₂, which was known to melt incongruently at 418 °C, has been prepared in pure phase from elemental rubidium and antimony in sealed tantalum crucibles. In accordance with the ribbon‐shaped antimonide anions, the compound crystallizes with extremely thin intergrown, mechanically and chemically very sensitive needles of dark‐metallic lustre. The crystal structure could be determined and refined using single crystal x‐ray data (monoclinic, space group C2/m, a = 1403(2), b = 414.0(4), c = 855.7(14) pm, β = 104.45(12)°, Z = 4, R1 = 0.0901) despite the poor quality of the crystals. It shows fused six‐membered rings of two‐ and three‐bonded Sb atoms forming ribbons running along the monoclinic b axis, which can be interpreted as sections of the elemental structure of antimony (d_Sb‐Sb = 281.9(5) and 286.0(9) pm respectively). The structure of RbSb₂ is thus closely related to that of KSb₂, which exhibits identical antimony anions. Compared to the potassium compound, the ribbons are reoriented against each so that the coordination number of the A counter ions is increased from 6 + 2 (for A = K) to 8 + 2 (for A = Rb). The results of a FP‐LAPW band structure calculation of RbSb₂ are used to explain the chemical bonding in this classical Zintl phase with a calculated indirect band gap of 0.38 eV.     

Synthesis,Structure, and High Temperature Thermoelectric Properties of Yb11Sb9.3Ge0.5

Zintl phase compounds with large unit cells and complex anionic structures such as Yb₁₁Sb₁₀ hold potential for being good thermoelectric materials. Single crystals of Ge‐doped Yb₁₁Sb₁₀ were synthesized using a molten Sn‐flux technique. Single crystal X‐ray diffraction data were obtained and resulted in a composition of Yb₁₁Sb_9.3Ge_0.5 which was verified by microprobe. Yb₁₁Sb_9.3Ge_0.5 is isostructural to Ho₁₁Ge₁₀, crystallizing in a body‐centered, tetragonal unit cell, space group I4/mmm, with Z = 4. The unit cell parameters of Yb₁₁Sb_9.3Ge_0.5 are a = 11.8813(4), c = 17.1276(13) Å with a volume of 2417.8(2) ų. These parameters correlate well with the structural refinement of previously published Yb₁₁Sb₁₀. The structure consists of 16 isolated Sb^3? anions, 8 dumbbells, 2 square planar rings and 44 Yb²⁺ cations. The Ge, doped in at 28 % occupancy, was found to be site specific, residing on the 2 square planar rings. Single crystal X‐ray diffraction is most consistent with the site that makes up the square ring being less than fully occupied. The doped compound is additionally characterized by X‐ray powder diffraction, differential scanning calorimetry and thermogravimetry. High temperature (300–1200 K) thermoelectric properties show that the doped compound has extremely low thermal conductivity (10–30 mW/cmK), lower than that of Yb₁₁Sb₁₀. Temperature dependent resistivity is consistent with a heavily doped semiconductor. Yb₁₁Sb_9.3Ge_0.5 shows p‐type behavior increasing from ～22 μV/K at room temperature to ～31 μV/K at 1140 K. The low value and the temperature dependence of the Seebeck coefficient suggest that bipolar conduction produces a compensated Seebeck coefficient and consequently a low zT.     

Ternary Antimonide EuSn3Sb4 and Related Metallic Zintl Phases

The ternary Zintl compound europium tin antimonide, EuSn₃Sb₄, has been synthesized at 900°C in the presence of a tin flux, and its structure has been determined by single-crystal X-ray diffraction methods. It crystallizes in the orthorhombic space group D¹⁶_2h-Pnma with a=9.954(2), b=4.3516(7), c=22.650(4) Å, and Z=4 at 22°C. EuSn₃Sb₄ is isostructural to SrSn₃Sb₄; it possesses channels defined by an anionic framework of shared SnSb₄ tetrahedra, SnSb₃ trigonal pyramids, and Sb–Sb zigzag chains, and it is filled by Eu²⁺ cations. Resistivity measurements indicate weakly metallic behavior for ASn₃Sb₄ (A=Eu, Sr) and the structurally related Ba₂Sn₃Sb₆. The anisotropic metallic nature of these compounds is explained through extended Hückel band structure calculations.     

Das Zintl-Konzept als Syntheseprinzip: Darstellung und Kristallstrukturen von K2Ba3Sb4 und KBa4Sb3O

Starting from the Zintl-Concept: Syntheses and Crystal Structures of K₂Ba₃Sb₄ and KBa₄Sb₃O The black, metallic lustrous, air sensitive compounds K₂Ba₃Sb₄ and KBa₄Sb₃O were prepared from melts of mixtures of the elements, in case of KBa₄Sb₃O with a stoichiometric amount of Sb₂O₃. K₂Ba₃Sb₄ crystallizes in the orthorhombic system, space group Pnma (a = 870.5(1) pm, b = 1770.2(2) pm, c = 923.6(1) pm, Z = 4) and is the first Sb compound with only [Sb₂]^4– dumbbells in the anionic partial structure. The compound KBa₄Sb₃O crystallizes in the tetragonal system, space group I4/mcm (a = 882.4(1) pm, c = 1659.4(2) pm, Z = 4). In this structure antimony forms [Sb₂]^4–-dumbbells and isolated ions Sb^3–. Each antimony ion of the dumbbells – in K₂Ba₃Sb₄ as well as in KBa₄Sb₃O – is coordinated in form of a bicapped skew trigonal prism. The isolated Sb^3– ions in KBa₄Sb₃O center bicapped tetragonal antiprisms, the O^2– ions occupy tetrahedral voids.     

Ba4Cr2US9: The First Chalcogenide Analogue of the Perovskite‐related (A3A′BO6)m(A3B3O9)n Family

The compound Ba₄Cr₂US₉, which crystallizes in space group P321, consists of one‐dimensional chains separated by Ba²⁺ cations. Each one‐dimensional chain comprises face‐sharing CrS₆ octahedra and US₆ trigonal prisms in the sequence oct oct tp oct oct tp with the U and Cr centers in a linear chain parallel to [001].     

Unusual Solid Solutions in the System Ge‐Sb‐Te: The Crystal Structure of 33R‐Ge4−xSb2−yTe7 (x,y ≈ 0.1) is Isostructural to that of Ge3Sb2Te6

Whereas for a series of layered compounds with the general formula (GeTe)_n(Sb₂Te₃)_m the stoichiometry allows to predict the structure type and the average thickness of the hexagonal atom layers, these rules are not generally applicable for GeTe‐rich compounds like Ge₄Sb₂Te₇. A 39R layer stacking is expected, however, single crystal diffraction studies reveal a 33R layered structure ( , a = 4.1891(5) Å, c = 62.169(15), R = 0.047) closely related to that of Ge₃Sb₂Te₆. This is also corroborated by the average layer thickness that can be determined from the strong reflections of powder patterns and exhibits a direct relation to the structure type. Mixed occupancy of cation positions with Ge and Sb and possibly defects allow this unusual range of homogeneity. Bulk material of the kinetically stable compound can be synthesized by quenching stoichiometric melts of the pure elements and subsequent annealing.     

Über Chalkogenolate. 121. Untersuchungen über N-Cyanomonothiocarbimidsäure 1. Darstellung und Eigenschaften von Alkalimetall-N-cyanomonothiocarbimaten

On Chalcogenolates. 121. Studies on N-Cyanomonothiocarbimic Acid. 1. Synthesis and Properties of Alkali Metal N-Cyanomonothiocarbimates The hitherto unknown N-cyanomonothiocarbimates M₂[SOC?N? CN] · H₂O, where M = Na, K, Rb, Cs, have been prepared by reaction of the corresponding alkali metal salt of cyanamide with COS. N-Cyanomonothiocarbimates react with sulfur to form the ion, which gives with an acid and with CH₃I the methyl compound . The reaction of the latter compound with H₂O₂ yields . All compounds have been characterized by means of diverse methods.     

Synthesis, structure and properties of the new rare-earth Zintl phase Yb11GaSb9

A new rare-earth rich Zintl phase Yb₁₁GaSb₉ was synthesized by direct fusion of the corresponding elements, and large single crystals of the compound were obtained from high temperature flux synthesis. Its crystal structure was determined by single-crystal X-ray diffraction to be orthorhombic in the non-centrosymmetric space group Iba2 (No. 45), Z=4 (R₁=3.24%, wR₂=6.40%) with , , measured at 90(3) K. The structure belongs to the Ca₁₁InSb₉-type and can be viewed as built of isolated Sb₄-tetrahedra centered by Ga, Sb-dimers and isolated Sb anions, which are separated by Yb²⁺ cations. Electron count according to the Zintl formalism suggests that the phase is electron-precise and charge-balanced, which is supported by the virtually temperature-independent magnetization for Yb₁₁GaSb₉. Electrical resistivity data from 2 to 400 K confirm that Yb₁₁GaSb₉ is a small band-gap semiconductor with room temperature resistivity , and low-temperature resistivity at 2 K . As such, Yb₁₁GaSb₉ and related compounds might be promising materials for thermoelectric applications, and currently, efforts to synthesize new members of this family and test their thermoelectric performance are under way.     

Tetrastrontium-digalliumoxide (Sr4Ga2O7)—synthesis and crystal structure of a mixed anion strontium gallate related to perovskite

Crystal growth experiments yielded single crystals of Sr₄Ga₂O₇. The title compound is monoclinic, space group P1c1, , , , β=90.643(6)°, , Z=16 (R1=0.041 for 7155 observed reflections and 660 parameters). The crystals showed twinning by pseudo-merohedry. Furthermore, the diffraction data exhibited the typical features of a superstructure. Sr₄Ga₂O₇ can be classified as a mixed anion gallate comprising insular [GaO₄]-groups and [Ga₃O₁₀]-trimers. Both anion groups are located in layers perpendicular to [100]. 32 symmetrically independent Sr-cations crosslink between the tetrahedral anion groups. Alternatively, the compound can be described as a 3×4×4 superstructure of ABO₃ perovskite, with 22.2% vacancies in the oxygen sublattice. The relationship with perovskite can be expressed in the following crystal chemical formula: Sr(Ga_2/3Sr_1/3)(O_7/9□_2/9)₃. A discussion of the structure in the context with other similar defect perovskites in presented.     

Der Sättigungsdruck von NbCl4 und NbBr4

Vapour Pressure of NbCl₄ and NbBr₄ The vapour pressur of solid NbCl₄ has been determined spectralphotometrically near 600 K: . NbCl₄ is monomolecular in the gaseous state. In the same way the vapour pressure of NbBr₄ has been found: .