Trigonal-prismatische Nb6-Einheiten in Verbindungen des Typs A3[Nb6SBr17] (A = Tl,K, Cs)

Trigonal-prismatic Nb₆-Units in Compounds of the Type A₃[Nb₆SBr₁₇] (A = Tl, K, Cs) The new compounds A₃[Nb₆SBr₁₇] (A = Tl, K, Cs) were synthesized and their lattice parameters were calculated from indexed X-ray powder patterns. An intensity measurement based on a single-crystal of Tl₃[Nb₆SBr₁₇] was performed with an automatic four-circle diffractometer (a = 1704.9(1) pm, b = 1862.8(3) pm, c = 932.51(7) pm; β = 90.747(7)°, V_m = 445.9(3) cm³/mol; C2/c, Z = 4). The structure refinement confirmed consistency with the Rb₃[Nb₆SBr₁₇] structure, found previously. The comparison of both structures yielded no significant differences concerning the distances within the sulfur-centered Nb₆S cluster core. Extended Hückel calculations revealed a maximum of the niobium–niobium overlap populations for (the actual present number of) 14 electrons occupying metal–metal bonding states.     

Phase Equilibria in the System Tl<Subscript>9</Subscript>SbSe<Subscript>6</Subscript>–TlSbSe<Subscript>2</Subscript>–Tl<Subscript>4</Subscript>SnSe<Subscript>4</Subscript>

For the first time, by differential thermal, X-ray powder diffraction, and microstructural analyses, phase equilibria in the ternary system Tl₉SbSe₆–TlSbSe₂–Tl₄SnSe₄ were investigated and the state diagram of the polythermal section Tl₄SnSe₄–Tl₃SbSe₃, the projection of the liquidus surface on the concentration triangle, and the isothermal section at 423 K were constructed. The types and coordinates of invariant processes, the lines of monovariant equilibria, and their temperature ranges were found. The formation mechanism and nature of solid solutions based on ternary compounds Tl₉SbSe₆ and TlSbSe₂ were studied in terms of crystal chemistry.     

Phase equilibria in the Tl-TlBr-Te system and thermodynamic properties of the compound Tl5Te2Br

The Tl-TlBr-Te composition region of the Tl-Te-Br phase diagram has been explored by DTA, X-ray diffraction, microhardness measurements, and electromotive force (emf) measurements relative to a thallium electrode in concentrations cells. The phase diagrams along a number of joins, the isothermal section at 400 K of the phase diagram, and a projection of the liquidus surface have been constructed. Extensive phase-separation areas, including a three-liquid-phase field in the Tl-TlBr-Tl₂Te subsystem, have been revealed. The homogeneity ranges and primary crystallization fields of phases have been mapped, and the coordinates of nonvariant and univariant equilibria in the T-x-y diagram have been determined. The standard thermodynamic functions of formation of the Tl₅Te₂Br compound and its standard entropy have been derived from emf data.     

Reciprocal system 3Tl2S + Bi2Se3 ↔ 3Tl2Se + Bi2S3

The reciprocal system 3Tl₂S + Bi₂Se₃ ? 3Tl₂Se + Bi₂S₃ has been investigated by DTA, X-ray powder diffraction analysis, and emf measurements. Some polythermal sections and the isothermal section at 500 K of the phase diagram and the projection of the liquidus surface of this system have been constructed, and the types and coordinates of the invariant and univariant equilibria have been determined. The existence of wide regions of quaternary solid solutions based on the binary compounds Tl₂S, Tl₂Se, Bi₂S₃, and Bi₂Se₃, and solid solutions between the temary compounds TlBiS₂ and TlBiSe₂ have been established.     

Phase equilibria and thermodynamic properties of the system Tl-TlBr-Se

The system Tl-Se-Br was studied in the region Tl-TlBr-Se by DTA, X-ray powder diffraction, emf measurements, and microhardness measurements. Several vertical sections, the isothermal section at 400 K, and the liquidus-surface projection were constructed. The quasi-binary sections TlBr-Tl₂Se, TlBr-TlSe, Tl₅Se₂Br-Tl, and Tl₅Se₂Br-TlSe allow the system Tl-TlBr-Se to be triangulated into five subordinate triangles. Wide immiscibility regions were discovered in the system, including a three-phase region in subsystem Tl₂Br-Tl₂Se-Se. Homogeneity and primary separation regions were determined, as well as the types and coordinates of invariant and monovariant equilibria on the T-x-y-diagram. From the results of emf measurements, the standard thermodynamic functions of formation were calculated for the compound Tl₅Se₂Br.     

Conductivity and Raman spectroscopy of new indium(I) and thallium(I) ionic conductors. In4CdI6, In2ZnI4, and Tl2ZnI4, and the related compound Tl4CdI6

The new compound Tl₂ZnI₄ has been prepared and characterized by Raman spectroscopy, powder X-ray diffraction, elemental analyses, and a partial binary phase diagram. The compounds In₄CdI₆, Tl₄CdI₆, and In₂ZnI₄, for which phase diagrams are available in the literature, were characterized by Raman spectroscopy and their identities were confirmed by elemental analyses and X-ray powder diffraction. Each of these materials, except Tl₄CdI₆, undergoes a sharp order-disorder phase transition at elevated temperatures that can be detected by the measurement of Raman spectra as a function of temperature. Conductivity measurements as a function of temperature, using both reversible and blocking electrodes, reveal a high ionic conductivity in the disordered, high-temperature phase. This work suggests that indium(I) and thallium(I) ionic conductors may exist, analogous to some well-known double salt conductors based on simple silver(I) and copper(I) halides. In addition, the present study demonstrates the usefulness of Raman spectroscopy in the characterization of heavy-metal ionic conductors.     

Interaction of components in the Tl<Subscript>2</Subscript>Se-Tl<Subscript>4</Subscript>SnSe<Subscript>4</Subscript>-Tl<Subscript>9</Subscript>SbSe<Subscript>6</Subscript> quasi-ternary system

The interaction in the Tl₂Se-Tl₄SnSe₄-Tl₉SbSe₆ quasi-ternary system was studied by differential thermal analysis, X-ray powder diffraction analysis, and mathematical modeling. The projection of the liquidus surface and a spatial phase diagram of the system were constructed. It was determined that this system is of the eutectic type with boundary solid solutions based on the initial components. No formation of new intermediate compounds in the quasi-ternary system was detected.     

Solid-phase equilibria and thermodynamic properties of the Tl2Se-As2Se3-Se system

The Tl₂Se-As₂Se₃-Se system in the equilibrium crystalline state was studied by differential thermal analysis, X-ray powder diffraction, and measurements of emf relative to a thallium electrode within the temperature range 300–400 K. An isothermal section of the phase diagram at 300 K was constructed. The formation of ternary compounds Tl₃AsSe₄, TlAsSe₂, and Tl₃AsSe₃ was confirmed, and the locations of their phase regions were determined. From the emf measurement data, the partial molar functions of thallium in alloys, the standard thermodynamic functions of formation, and the standard entropies of the above ternary compounds were calculated.     

Reciprocal system 3Tl<Subscript>2</Subscript>S + Sb<Subscript>2</Subscript>Se<Subscript>3</Subscript> ⇆ 3Tl<Subscript>2</Subscript>Se + Sb<Subscript>2</Subscript>S<Subscript>3</Subscript>

Phase equilibria in the reciprocal system 3Tl₂S + Sb₂Se₃ ? 3Tl₂Se + Sb₂S₃ are investigated by DTA, X-ray powder diffraction, and emf measurements. Some polythermal sections, the isothermal section of the phase diagram at 400K, and the liquidus-surface projection for this system are constructed. The types and coordinates of invariant and univariant equilibria are determined. It is shown that the system is non-diagonal. Broad regions of solid solutions are found on the basis of the binary compounds Tl₂S and Tl₂Se and along the boundary system Sb₂S₃-Sb₂Se₃ and the sections Tl₃SbS₃-Tl₃SbSe₃, TlSbS₂-TlSbSe₂, and TlSb₃S₅-TlSb₃Se₅ of the phase diagram.     

Thiobromokomplexe von Arsen und Antimon Darstellung und Kristallstrukturen von (PPh4)2[As2SBr6] · CH2Br2 und (PPh4)2[Sb2SBr6] · CH2Br2

Thiobromo Complexes of Arsenic and Antimony. Preparation and Crystal Structures of (PPh₄)₂[As₂SBr₆] · CH₂Br₂ and (PPh₄)₂[Sb₂SBr₆] · CH₂Br₂ (PPh₄)₂[As₂SBr₆] · CH₂Br₂ is formed by the reaction of As₂S₃, PPh₄I and HI in dibromomethane. It can also be obtained, as well as (PPh₄)₂[Sb₂SBr₆] · CH₂Br₂, from (PPh₄)₂[As₂Br₈] and (PPh₄)₃[Sb₂Br₉], respectively, with bistrimethylsilylsulfide. The crystal structures of the title compounds were determined by X-ray diffraction. They are isotypic with (PPh₄)₂[As₂SCl₆] · C₂H₄Cl₂. In the anions [M₂SBr₆]^2? the M atoms (As or Sb) have a distorted octahedral coordination, the two octahedra share acommon face with one bridging S and two Br atoms; the lone electron pairs occupy the trans positions to the S atom. Crystal data: triclinic, space group P1 , Z = 2; (PPh₄)₂[As₂SBr₆] · CH₂Br₂, a = 119.1, b = 1203.6, c = 2067.5 pm α= 94.89, β = 97.78, γ = 112.20°, 3046 independent observed reflexions, R = 0.083; (PPh₄)₂[Sb₂SBr₆] · CH₂Br₂, a = 1198.9, b = 1224.3, c = 2085.5pm, α = 95.04, β = 98.48, γ = 112.13°C, 2380 reflexions, R = 0.079.     

Diagramme de phases du système Tl2OMoO3

Six thallium(I) molybdates with numerous allotropic modifications have been found in the binary system Tl₂OMoO₃; Tl₄MoO₅, Tl₂Mo₂O₇, Tl₈Mo₁₀O₃₄ (three forms), and Tl₂Mo₇O₂₂ (two forms) melt incongruently; Tl₂MoO₄ and Tl₂Mo₄O₁₃ which are trimorphic melt congruently. For the most part, the compounds were characterized by their powder diagram and by their IR spectrum which allowed comparisons with alkaline molybdates.     

Pentabromothio-diarsenat und -diantimonat: Darstellung,Schwingungsspektren und Kristallstrukturen von PPh4[As2SBr5] und PPh4[Sb2SBr5]

Pentabromothio-diarsenate and -diantimonate: Preparation, Vibrational Spectra, and Crystal Structures of PPh₄[As₂SBr₅] and PPh₄[Sb₂SBr₅] The title compounds were obtained in CH₂Br₂ from PPh₄Br, HBr and As₂S₃ or Sb₂S₃, respectively. Their i.r. and Raman spectra are reported. Their crystal structures were determined by X-ray diffraction. Crystal data: PPh₄[As₂SBr₅], monoclinic, space group P2₁/n, Z = 4, a = 1192.3, b = 1528.1, c = 1618.0 pm, β = 95.53°, isotypic with PPh₄[As₂SCl₅] (structure determination with 1539 observed reflexions, R = 0.052); PPh₄[Sb₂SBr₅], triclinic, space group P1 , Z = 2, a = 1044,8, b = 1207.1, c = 1307.8 pm, α = 104.77, β = 108.63, γ = 98.34° (2398 observed reflexions, R = 0.032). Both ions, [As₂SBr₅]^? and [Sb₂SBr₅]^?, have the same general structure: including the lone electron pairs, the As and Sb atoms have distorted trigonal-bipyrimidal coordination, two bipyramids sharing a common edge with sulfur and bromine as bridging atoms. The [As₂SBr₅]^? ions are associated to chains via As…Br contacts, the [Sb₂SBr₅]^? ions form pseudodimeric units by Sb…S and Sb…Br contacts. Whereas the crystal packing of the As compound is similar to that of other PPh₄⁺ compounds having a cation to anion ratio of 1:1, the Sb compound shows the packing principle known for 2:1 compounds.     

Phase equilibria in quasi-binary sections of the Tl-Sn-S system

Phase equilibria in quasi-binary sections of the Tl-Sn-S system: (I) Tl₄SnS₄-SnS, (II) Tl₂SnS₃-SnS, (III) S-Tl₄SnS₄, (IV) S-Tl₂SnS₃, (V) Tl-SnS, and (VI) Tl₂S-SnS were studied by differential thermal analysis and X-ray powder diffraction. It was found that systems I and II are characterized by the eutectic type of interaction, the phase diagrams of systems III and IV are of the eutectic type with a degenerate eutectic at the sulfur melting point, and the phase diagram of system V is of the fourth type according to Roozeboom. Phase equilibria in system VI were specified.     

Thallium alloys of the rare earth: Sm?TI Phase diagram and molar volumes of the rare earth thallides

The Sm? Tl system has been studied by differential thermal, metallographic and X-ray analyses. The following intermediate phases were observed: Sm₂Tl (decomposes at 1030 ± 10°C); Sm₅Tl₃ (decomposes at 1060 ± 10°C); SmTl (melting point, 1220 ± 20°C); Sm₃Tl₅ (decomposes at 940 ± 10°C); SmTl₃ (melting point, 870 ± 5°C). Three eutectics occur: β-Sm—Sm₂Tl (840 ± 10°C, 18.0 ± 0.5 at % Tl); Sm₃Tl₅—SmTl₃ (860 ± 5°C, 72.0 ± 0.5 at % Tl); SmTl₃—β-Tl (～303°C, greater than 99.5 at % Tl); there is an eutectoidal reaction at 760 ± 10°C and 10 ± 1 at % Tl (decomposition of β-Sm phase). Following crystal structures have been determined or confirmed: Sm₂Tl hexagonal hP6—Ni₂In-type, Sm₅Tl₃ tetragonal tI32—W₅Si₃-type, SmTl cubic cI2—W or cP2—CsCl-type, SmTl tetragonal tP4—AuCu I-type, Sm₃Tl₅ orthorhombic oC32—Pu₃Pd₅ like-type, SmTl₃ cubic cP4—AuCu₃-type. The characteristics of the phase diagram and the molar volumes of the Sm? Tl compounds are compared with those of other RE? Tl alloys and briefly discussed.     

Quasi-ternary system Tl<Subscript>2</Subscript>Se-AgTlSe-TlBiSe<Subscript>2</Subscript>

The quasi-ternary system Tl₂Se-AgTlSe-TlBiSe (A) has been investigated by DTA, X-ray powder diffraction, microstructural analysis, and microhardness measurements. Polythermal sections AgTlSe-TlBiSe₂, AgTlSe-Tl₉BiSe₆, [Ag_0.5Tl_1.5Se]-TlBiSe₂, Tl₂Se-AgBiSe₂ (0–50 mol % AgBiSe₂), an isothermal section at 500 K, and the projection of the liquidus surface of system A have been constructed. It has been shown that the quasi-binary join AgTlSe-Tl₉BiSe₆ divides system A into two subordinate triangles, namely, Tl₂Se-Tl₉BiSe₆-AgTlSe (B) and AgTlSe-Tl₉BiSe₆-TlBiSe₂ (C). The phase diagram of subsystem B involves a univariant eutectic equilibrium while subsystem C involves an invariant eutectic equilibrium. The ternary eutectic has the coordinates 650 K, 10 mol % TlBiSe₂, and 61 mol % AgTlSe. A continuous series of solid solutions (0–12 mol % AgTlSe) has been found along the Tl₂Se-Tl₉BiSe₆ bordering system. The homogeneity region of TlBiSe₂ extends to 5 mol %.     

Phase equilibria in the Tl2Te-PbTe-Bi2Te3 system

Phase equilibria in the Tl₂Te-PbTe-Bi₂Te₃ system were studied by differential thermal analysis, X-ray powder diffraction, and microhardness measurements. Some polythermal sections and isothermal (at 600 and 800 K) sections of the phase diagram and a projection of the liquidus surface were constructed. It was shown that the system is characterized by the formation of solid solutions with the Tl₅Te₃ structure (??) and solid solutions based on PbTe (??₁), Tl₂Te (??), Bi₂Te₃ (??), and two TlBiTe₂ (??₂ and ?á?₂) phases. Their homogeneity regions were determined. The liquidus surface consists of the primary crystallization fields of the ??-, ??₁-, ?á?₂-, and ??-phases and the compounds PbBi₂Te₄ and PbBi₄Te₇. The liquidus of the ?? phase is degenerate. The primary crystallization fields of the phases were determined, and the types and coordinates of in- and monovariant equilibria were found.     

Interaction in the systems TlBiSe<Subscript>2</Subscript>–Tl<Subscript>9</Subscript>BiSe<Subscript>6</Subscript>–PbSe and Tl<Subscript>9</Subscript>BiSe<Subscript>6</Subscript>–Tl<Subscript>4</Subscript>PbSe<Subscript>3</Subscript>–PbSe

Phase equilibria in the systems TlBiSe₂–Tl₉BiSe₆–PbSe and Tl₉BiSe₆–Tl₄PbSe₃–PbSe were studied by differential thermal, X-ray powder diffraction, and microstructural analyses. State diagrams of the quasi-binary sections Tl₉BiSe₆–Tl₄PbSe₃, TlBiSe₂–PbSe, and Tl₉BiSe₆–PbSe were constructed, and so were projections of liquidus surfaces and isothermal sections at 600 K for the secondary quasi-ternary systems TlBiSe₂–Tl₉BiSe₆–PbSe and Tl₄PbSe₃–Tl₉BiSe₆–PbSe. The coordinates of invariant points and the boundaries of solid solutions were determined.     

Phase equilibria in the Tl2Te-SnTe-Bi2Te3 system

phase equilibria in the Tl₂Te-SnTe-Bi₂Te₃ system were studied by differential thermal analysis (DTA), X-ray powder diffraction, and microhardness measurements. Some polythermal sections and isothermal (at 600 and 800 K) sections of the phase diagram and a projection of the liquidus surface were constructed. It was shown that the system is characterized by the formation of solid solutions with the Tl₅Te₃ structure (δ) and solid solutions based on SnTe (γ₁), Tl₂Te (α), Bi₂Te₃ (β), and two TlBiTe₂ (γ₂ and γ′₂) phases. Their homogeneity regions were determined. The liquidus surface consists of the primary crystallization fields of the β-, γ₁-, γ′₂-, and δ phases and the compounds SnBi₂Te₄ and SnBi₄Te₇. The liquidus of the α phase is degenerate. The primary crystallization fields of phases were determined, and the types and coordinates of in- and monovariant equilibria were found.     

Synthesis and crystal structure of the alkaline-earth thallates MnTl2O3+n (M=Ca,Sr)

The phases present in the Tl₂O₃–MO system, where M=Ca and Sr, have been synthesised and characterised using powder neutron diffraction data. The structures of the phases known to exist in the Ca_nTl₂O_3+n system with n=1, 1.5, 2 and 3 have been refined and the oxycarbonate phase with composition Ca₄Tl₂O₆CO₃ has been identified. In the Sr_nTl₂O_3+n system, the structures of the phases with n=1, 2 and 3 have also been refined. The M_nTl₂O_3+n phases with M=Ca and Sr and n=1–3 are related to the lillianite structure while the n=4 compound is an oxycarbonate that has been found to crystallise in I4/mmm symmetry for M=Ca and in three different modifications with space groups P4/mmm, I4/mmm and Pmmm for M=Sr, depending on the ordering of the carbonate groups. The relationships between these structures are discussed and comparisons are made to the previously published structures determined from X-ray powder diffraction data.     

Zur Neuuntersuchung des Phasendiagramms TlI—SnI2

Redetermination of the Phase Diagram TlI—SnI² A reinvestigation of the phase diagram TlI—SnI₂ revealed the existence of a not yet known ternary 4 : 1 compound of the formula Tl₄SnI₆, which decomposes peritectoidally at 229^°C. The congruent melting points of the other three ternary compounds in the system, Tl₃SnI₅, TlSnI₃, and TlSn₂I₅, at 329^°C, 292^°C and 307^°C, respectively, agreed well with former specifications. However the polymorphic transitions of the compounds Tl₃SnI⁵ and TlSn₂I₅ described by other authors could not be verified.