[en] Glass formation in the TeO₂-MoO₃-CeO₂ system was investigated and low melting stable glasses with up to 30 mole-% CeO₂ were synthesized. Infrared spectral investigations were used to develop structural models for the vitreous ternary system. CeO₂ mainly acts as a modifier without affecting appreciable changes to the glass network and coordination of the glass formers. Glasses in the molybdenum-rich compositional range are mainly composed of [MoO₆] and [TeO₃] polyhedra, whereas low MoO₃-containing glasses consist of [TeO₄] groups and isolated [MoO₄] units. On the whole, the basic structural polyhedra participating in the formation of the three-dimensional glass forming network are therefore [TeO₄], [TeO₃], [MoO₆], [MoO₄], and [Mo₂O₈] (or [MoO₅]) units. The structural affinity of some ternary glasses to crystalline Ce₄Mo₁₁Te₁₀O₅₉ is pointed out. The high electrical conductivity of the ternary glasses is interpreted on the basis of electron hopping between transition ions in different valence states and contributions due to the Te(IV) network. (author)

[en] Attempts have been made to prepare crystals of solid solution series having block structures with building elements of [3x4] [4x4], [4x5], and [5x5] octahedra in the system Nb₂O₅/WO₃/NbO₂ by chemical transport reactions with various transport agents. Crystals of about 6 mm in length of these compounds, however, have been prepared by a nearly isothermal chemical transport with HgCl₂ as a mineralizer. The compositional limit of the four solid solution series has been somewhat extended compared to reported values. (author)

[en] This contribution deals with X-ray single crystal investigations of (I) Nd_1.5Sr_0.5(Cu,Al)O₄ and (II) Nd₂(Cu,Ni)O₄. I belongs to the K₂NiF₄-type [a = 3.7338; c = 12.7378 A; space group D_4h¹⁷-I4/mmm; Z = 2]. II show Cu²⁺ and Ni²⁺ with statistic distribution and orthorhombic distorted K₂NiF₄-type [a = 5.3653; b = 5.4364; c = 12.4599 A; space group C_2v¹⁷-Cc2a; Z = 4]. I and II loose the originally planar CuO₄ polyhedra of the Nd₂CuO₄ type. (author)

[en] For the first time single crystals of Na₄WO₅ were prepared by heating of mixtures of Na₂WO₄ and Na₂O [Na:W = 4.2:1, Ni-cylinder, 725 ⁰C, 28 d). Four-circle-diffractometer data [PW 1100, 1900 I_o(hkl), ω-2Θ scan, AgKα-bar-radiation, R = 6.5%, R_w = 5.7%]determine the triclinic structure of Na₄WO₅ with a = 569.4(2), b = 847.7(2), c = 565.7(1) pm, α = 101.29(2)⁰, β = 102.25(3)⁰, γ = 109.20(3)⁰. It is isotypic with the NaCl-type of structure Li₄WO₅. By heating Na₄WO₅ with K₂O [Na:K:W = 4:3:1, Au-tube, 750 ⁰C, 35 d] colourless single crystals of KNa₃WO₅ were obtained for the first time. The structure determination [four-circle-diffractometer data, PW 1100, ω-2Θ scan, 943 I₀(hkl), MoKα-bar-Strahlung R = 4.9%, R_w = 3.9%] proves space group C2/m with a = 907.8(3), b = 753.9(2), c = 911.8(3) pm, β = 104.07(4)⁰, Z = 4. The structure is characterized by undulating layers of Na, W and O and two different kinds of channels. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECON, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed. (author)

[en] Reaction of liquid hydrogensulfide, H₂S and D₂S respectively, with cesium at room temperature in pressure resistant glass tubes quickly gives the crystalline hydrogensulfides, CsHS and CsDS. The compounds are characterized by thermochemical, X-ray, and neutron diffraction data. Three solid phases of CsDS are observed as a function of temperature: CsDS ≥ 210 K: Pm3m, N = 1, a = 4.3165(8) A CsCl-type with quasifree rotation of anions ≤ 210 K to ≤ 100 K: P4/mbm, N = 2, a = 5.853(3) A, c = 4.538(3) A distorted CsCl-type with a two side jump position of deuterium linearly aligned across sulfur at 9 K: I4/m, N = 8, a = 8.224(2) A, c = 9.040(3) A with fixed positions for the anion. Changes in chemical bonding are discussed with respect to temperature and in comparison with alkali metal hydroxides, amides, halides, and further hydrogensulfides. (author)

[en] High temperature reaction using reducing atmosphere lead to the new compounds (I) SrCr₁₀O₁₅ and (II) BaCr₁₀O₁₅. Single crystal X-ray investigations show orthorhombic symmetry: space group D_2h¹⁸-Ccmb; I: a = 10.059; b = 11.406; c = 9.224 A; II: a = 10.126; b = 11.491; c = 9.392 A; Z = 4. Cr²⁺/Cr³⁺ are octahedral coordinated by O^2-. Inside a CrO₆-octahedral network are cavities comperable with those of some polyacids filled by Sr²⁺ or Ba²⁺ ions. (author)

[en] For the first time Cs₂Li₁₄[Tb₃O₁₄] has been prepared as orange single crystals from Cs₂TbO₃ and Li₂O (Tb:Li = 1:5) [550 ⁰C, 21 d, sealed Au-tube]. Structure refinement [four-circle diffractometer data, PW 1100, MoKα-bar radiation, 660 I₀(hkl), R = 4.8%, R_w = 3.4%, Immm, A = 1293.5(8), b = 792.6(3), c = 740.4(3) pm, Z = 2, d_roe = 4.65] confirms isotypy with K₂Li₁₄[Pb₃O₁₄]. K₂Li₁₄[Zr₃O₁₄] has also been prepared as colorless single crystals from K₂O, Li₂O, and ZrO₂ (K:Li:Zr = 1:4:1.5), [900 ⁰C, 14 d, closed Ni-cylinder) and investigated by X-ray [612 I₀(hkl), four-circle diffractometer data, PW 1100, MoKα-bar radiation, R = 5.9%, R_w = 5.3%, Immm, a = 1244.6, b = 776.4, c = 724.3 pm, Z = 2]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, the latter derived from Mean Effective Fictive Ionic Radii, MEFIR, are calculated. A detailed comparison of the structures is carried out. (author)

[en] The compounds Na₆MnS₄, Na₆MnSe₄, Na₆MnTe₄, K₆MnS₄, K₆MSe₄ and K₆MnTe₄ were synthesized by the reaction of alkali metal carbonates with chalcogen and Mn or MnCO₃ in a stream of hydrogen charged with chalcogen. Structural investigations on single crystals show that all six compounds crystallize in isotypic atomic arrangements (Na₆ZnO₄-type, space group P6₃mc), which are characterized by isolated [MnX₄] tetrahedra. The magnetic susceptibilities show Curie-Weiss behaviour. At low temperatures there are obviously antiferromagnetic interactions increasing from the sulfides to the tellurides and from the sodium compounds to the potassium compounds. (author)

[en] The new intercalation compound TaS₂ · 0.5 C₄NH₅ is obtained by reaction of 2H-TaS₂ with surplus pyrrol in a closed system at 473 K. The powder diffraction pattern can be indexed based on a hexagonal unit cell with lattice parameters a = 3.315(1) and c = 22.256(7) A. The temperature induced deintercalation has been studied from 293 to 1073 K. From 677 to 725 K there is a plateau in the TG curve which is attributed to the staging compound TaS₂ · 0.33 C₄NH₅. Up to 1073 K a total mass of 10% has been squeezed out. From 300 to 50 K there is a nearly linear decrease of the resistivity of TaS₂ · 0.5 C₄NH₅ while below 40 K a pronounced ascent has been observed followed by a transition to superconductivity at T ≤ 7.5 K. The degree of polymerized pyrrol in the host structure has been studied using XPS and a N1s signal, 5 eV broad, was monitored which indicates the existence of several sites of differently bonded N atoms. (author)

[en] Synthesis and crystallographic data on 29 new phases in this family are given. A survey of the crystal chemistry of the complete family, containing 59 phases to date, is presented. The family contains at least seven structural variations, two of which are the pollucite, CsAlSi₂O₆ and leucite, KAlSi₂O₆ structures. Correlations between cation size and structure type are presented. Unusual variations in unit cell dimensions as a function of cation size are discussed and the possible relevance of the 'partially collapsed framework' concept of Taylor and Henderson indicated. (author)