Cs4GeTe6, ein o-Pertelluridogermanat (IV)

The new compound Cs₄GeTe₆ crystallizes in the monoclinic system, space group P2₁/n (No. 14) with the lattice constants a = 1784.5(8) pm, b = 1398.1(6) pm, c = 786.7(4) pm, β = 101.6(1)°. The Ge-atoms are tetrahedrally coordinated by two single Te-atoms and two “end on” bonded Te₂-dumbbells, forming hitherto unknown discrete GeTe₆^4?-anions.     

Seebeck coefficient of K2SO4

The thermopotential of the cell (SO₂+O₂), Pt/K₂SO₄/Pt, (SO₂+O₂)′ was measured, and a Seebeck coefficient of 1.6 mV/°C was obtained. This value is higher than that of most salts that have been measured to date. The high Seebeck coefficient has implications in the use of the cell in SO₂ gas measurements.     

Superstructure of potassium selenate K2SeO4

Structural phase changes in K₂SeO₄ are studied by using a low-temperature X-ray diffraction technique. As shown by Aiki et al. the phase changes occur at 129.5 K (T_M) from the room-temperature phase to the M phase and at 93 K (T_C) from the M to the Ferro phases. A superstructure along the a axis is observed both in the M and Ferro phases with a period three times as long as that at room temperature. The space group is determined to be Pnam or Pna2₁ in the M phase, while in the Ferro phase non-centrosymmetric Pna2₁ is unique. The superstructure is attributed to rather small, atomic displacements parallel to the a plane. The following lattice constants at room temperature (302±1 K) are determined from back-reflection Weissenberg photographs: a₀ = 7.6479±2, b₀ = 10.4656±4 and $\text{c}{}_0\text{= 5.9963±2}\text{A}\text{?}$.     

A TSC investigation of K2ZnF4 and KZnF3

Thermal stimulated polarization (TSP) and depolarization (TSD) currents with two specific peaks were obtained in insulated undoped and trivalent cation doped K₂ZnF₄ and undoped KZnF₃. It is shown that the high temperature peaks are caused by a surface polarization by point defects, the low temperature peaks in doped samples by defect-impurity complex reorientation. Basing on the data, the parameters of the charge transport and the defect order are discussed.     

Crystal structure of K4[H2J2O10].8H20

Crystals of K₄ [H₂J₂O₁₀] 8H₂O belong to the triclinic system, space group P 1 with a = 7.161 (2) $\text{A}\text{?}\text{, b}\text{= 10,553}$ (5) $\text{A}\text{?}\text{, c}\text{= 7,081}$ (2) $\text{A}\text{?}\text{, α = 98°1′}$, β = 117°8′, γ = 90°6′ and Z = 1. The crystal structure has been determined on the basis of photographic data from 877 independent reflections, with the final R value of 6,6%. The iodine atoms are surrounded by a distorted octahedra consisting of five oxygen atoms and one OH group. The average J-O distance is 2.03 Å. There are 2 independent K atoms in the structure. K(1) has a coordination number of eight, while K(2) is surrounded by 6 (5 water molecules + one OH group) nearest neighbours.     

Crystal growth and structure determinations of potassium hafnates: K2Hf2O5 and K4Hf5O12

Crystals of K₂Hf₂O₅ and K₄Hf₅O₁₂ were grown from molten potassium hydroxide flux. The crystal structures were determined by single-crystal X-ray diffraction. K₂Hf₂O₅ crystallizes in the space group Pnna of the orthorhombic system, with unit cell dimensions of a = 5.780(1) Å, b = 10.640(2) Å, and c = 8.666(2) Å. This compound contains infinite chains of HfO₆ octahedra that form a channel structure. K₄Hf₅O₁₂ crystallizes in the space group of the trigonal system, with unit cell dimensions of a = 5.7877(2) Å and c = 10.3693(7) Å. This compound possesses a layered structure with six-coordinate Hf in three different coordination environments (trigonal prismatic, distorted octahedral, and regular octahedral).     

New [K2NiF4] compounds with mixed B-ions

The synthesis and characterization of new [K₂NiF₄]-type compounds is described. New tolerance factors for this structure are given, and the lack of ordering is discussed.     

Syntheses of hollandite type Rb2Cr8O16, K2Cr2V6O16 and K2V8O16

Hollandite-type compounds, Rb₂Cr₈O₁₆, K₂Cr₂V₆O₁₆ and K₂V₈O₁₆, were synthesized under high P-T conditions up to 1200°C and 7GPa. The structural refinement using a single crystal of Rb₂Cr₈O₁₆ confirms that the structure is similar to that of K₂Cr₈O₁₆. Magnetic measurements indicate that Rb₂Cr₈O₁₆ is ferromagnetic below 295K, K₂Cr₂V₆O₁₆ paramagnetic down to 77K and K₂V₈O₁₆ has susceptibility anomaly at 175K. These compounds are all semiconductive and show discontinuities in temperature-resistivity curves at points corresponding to magnetic anomalies.     

New palladium phosphate complexes: K2PdP2O7 and K3.5Pd2.25(P2O7)2 synthesis, single crystal structure and conductivity

Two new diphosphate complexes containing potassium and palladium, K₂PdP₂O₇ and K_3.5Pd_2.25(P₂O₇)₂, have been synthesized and characterized by single crystal X-ray diffraction. K₂PdP₂O₇ exists with layers formed of linked PdP₂O₇ polyhedra, between which are found the potassium ions. K_3.5Pd_2.25(P₂O₇)₂ with a Pd/P₂O₇ ratio of 1.125:1 crystallizes with tunnels of various sizes in which are found the potassium ions. Conductivity measurements reveal the material to be conducting.     

Ionic conductivities of Na2Ti3O7, K2Ti4O9 and their related materials

Ionic conductivities were measured on the polycrystalline samples of layered titanates, Na₂Ti₃O₇ and K₂Ti₄O₉, and their derivatives. The activation energies and the prefactors of the conductions were 0.70 eV and 7.9 × 10 (Ωcm)^?1K for Na₂Ti₃O₇ and 0.81 eB and 1.1 × 10³ (Ωcm)^?1K for K₂Ti₄O₉. A small amount of Nb₂O₅ was doped to these titanates substituting TiO₂. Remarkable enhancements of ionic conductivities were observed with the doping. A new metastable phase, Li₂Ti₃O₇, was prepared by ion-exchange of Na₂Ti₃O₇ and its ionic conductivity was measured.     

Large-scale hydrothermal synthesis of WO3 nanowires in the presence of K2SO4

WO₃ nanowires were fabricated by a hydrothermal method in the presence of K₂SO₄. The nanowires exhibit a well crystallized one-dimensional structure with 10 nm in diameter and several microns in length. Effects of other alkali salts (KNO₃, NaNO₃ and Na₂SO₄) on the morphologies of WO₃ nanocrystals were also investigated. The important role of K₂SO₄ salt in the WO₃ nanowires synthesis has been demonstrated.     

Hydrothermal Crystallization in the Systems La2(CO3)3 ? 6H2O-CaCO3(BaCO3)-R-H2O (R = Na2CO3, K2CO3, NaHCO3, KHCO3, NaCl, NH4Cl, CO(NH2)2)

Crystallization in the systems La₂(CO₃)₃ ⋅ 6H₂O-CaCO₃(BaCO₃)-R-H₂O (R = Na₂CO₃, K₂CO₃, NaHCO₃, KHCO₃, NaCl, NH₄Cl, CO(NH₂)₂) was studied under hydrothermal conditions (400–450°C). The solid reaction products were found to contain LaOHCO₃ and NaLa(CO₃)₂. Detailed thermal decomposition schemes were proposed for these phases, and their lattice parameters were refined. __________ Translated from Neorganicheskie Materialy, Vol. 41, No. 11, 2005, pp. 1366–1372. Original Russian Text Copyright ? 2005 by Nikol'skaya, Dem'yanets.     

K2(Rb2,Cs2,Tl2)TeBr6(I6) and Rb3(Cs3)Sb2(Bi2)Br9(I9) perovskite compounds

We systematize available experimental data on the crystal structure of the ternary halides K₂(Rb₂,Cs₂,Tl₂)TeBr₆(I₆) and Rb₃(Cs₃)Sb₂(Bi₂)Br₉(I₉), analyze the general trends in the properties of their single crystals, and examine the key features of the physicochemical interaction in related systems.     

Cs2Si2Te6, ein polypertelluridosilikat (IV)

The new compound Cs₂Si₂Te₆ crystallizes in the monoclinic system (space group: Cc, No. 9) with the lattice constants a = 828.5(4) pm, b = 1393.5(6) pm, c = 1340.4(6) pm, ß = 100.35(12)°.Fivefold Si₂Te₃-rings, each formed by two SiTe₄ tetrahedra, connected by common Te atoms and Te-Te groups, are linked by Te bridges to infinite strings.     

Effect of plating conditions for electroless Ni deposition on catalytic properties of K2MoO4/Ni-SiO2 catalyst

A series of K₂MoO₄/Ni-SiO₂ catalysts with Ni-SiO₂ as support for methanethiol synthesis from H₂S-rich synthesis gas were prepared and characterized by BET, ESR, XPS and HRTEM techniques. The optimum electroless plating condition was explored for the preparation of Ni-SiO₂ support. Physicochemical characterization results show that the Ni-SiO₂ support prepared under the alkaline condition and relatively high plating temperature makes molybdenum species dispersing more uniformly, leading to an appropriate K/Mo atomic ratio on its surface owing to the advantage of surface morphology. The sulfurized catalyst was found to have a suitable pore diameter distribution and a suitable molar ratio of S₂²⁻/S²⁻ (close to 1) on the surface of the catalyst, which were confirmed to be in favor of the improvement of the catalytic performance of the catalyst.     

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.     

The preparation and growth of pure single crystals of K2Pt(CN)4Br0.3·3H2O and K2Pt(CN)4Cl0.3·3H2O

The preparation of pure single crystals of K₂Pt(CN)₄Br_0.3·3H₂O and K₂Pt(CN)₄Cl_0.3·3H₂O has been investigated. Crystals with reproducible d.c. conductivity and dielectric constants were obtained only when the mixed valence platinum salt contained one halide. The bromide complex was particularly susceptible to contamination by chloride, and a preparation scheme is presented which excludes the unwanted halide. The best quality crystals were grown by slow evaporation of solutions which were 1 molar in urea and 0.1 molar in the appropriate potassium halide.     

Evidence for the non-existence of a bragg reflection superlattice in K2Pt(CN)4Br0.3·3H2O and K2Pt(CN)4Cl0.3·3H2O

An extensive and careful search for superlattice reflections in K₂Pt(CN)₄Br_0.3·3H₂O and K₂Pt(CN)₄Cl_0.3·3H₂O has yielded no evidence for an enlarged cell. Six individual crystals obtained via different preparative methods, from solutions at several pH values from 2 to 10, and subjected to a variety of conditions of temperature and humidity have been examined. All samples gave identical cells and nearly identical diffraction patterns. Two samples gave a single weak non-integral 00l neutron reflection which is not explainable by order contamination or double diffraction.     

Polarized spectral properties of Tm:K5Bi(MoO4)4 crystal

Trivalent thulium-doped K₅Bi(MoO₄)₄ single crystals were grown by the Czochralski method. Its polarized absorption and fluorescence spectra and fluorescence decay curves were recorded at room temperature. On the basis of the Judd-Ofelt theory, the spectral parameters of the Tm³⁺:K₅Bi(MoO₄)₄ crystal were calculated. The cross relaxations between Tm³⁺ ions were analyzed. The emission cross sections of the ³F₄ → ³H₆ transition were obtained by the Fuchtbauer-Ladenburg formula and then the gain cross sections around 1.9 μm were calculated. The peak emission cross section and width of emission band around 1.9 μm are comparable to those for Tm³⁺:YAG and the tunable range is about 280 nm for the potential ∼1.9 μm laser operation via the ³F₄ → ³H₆ transition.     

High pressure synthesis of K3V(VO4)2, a new compound with glaserite type structure

K₃V(VO₄)₂ with glaserite type structure was synthesized from KVO₃ in a modified Belt-type apparatus at 35 kbar and 800°C. The compound is the first glaserite-like phase with tetrahedral (VO₄)^3?-anions and V³⁺ in octahedral coordination.