Klaus-Jürgen Range

New compounds A2−xV8O16 (A = K,Tl) with hollandite type structure

Abstract K2V8O16, K1.8V8O16 and Tl1.74V8O16 were synthesized by high pressure- high temperature treatment of KVO3 and TlVO3 in a modified Belt-type apparatus. The compounds crystallize tetragonal, space group I4/m. They are the first well-characterized Vanadium-hollandites and show a remarkable high occupation of the tunnel sites with univalent cations.

β-PtO2: High pressure synthesis of single crystals and structure refinement

Abstract Single crystals of β-PtO2 have been grown from PtKC103-mixtures at 40 kbar, 1500 °C in a modified Belt-type apparatus using Pt-capsules. The crystals are orthorhombic, space group Pnnm, with a=4.4839(3) A, b=4.5385(6) A, c=3.1360(6) A and Z=2. Single crystal X-ray data confirmed the structure to be CaCl2-type, a distorted variant of the rutile structure. The PtO distances are 2 × 1.989(4) and 4 × 2.003(4) A, the shortest oxygenoxygen distance is 2.494(5) A. A discussion of some geometrical features is presented.

Homogene, abschreckbare hochdruckphasen in den systemen AgSbSe2 - AgInSe2 und AgBiSe2 - AgInSe2

Abstract Quenchable, homogenous high pressure phases in the systems AgSbSe 2 - AgInSe 2 and AgBiSe 2 - AgInSe 2 could be synthesized from appropriate mixtures of the ternary compounds in a belt-type high-pressure apparatus. The phases AgSb 1−x In x Se 2 crystallize with the rocksalt structure at the Sb-rich side and with the α-NaFeO 2 structure at the In-rich side of the phase diagram. All AgBi 1−x In x Se 2 samples have α-NaFeO 2 -structure. The high temperature B1-type modification of AgBiSe 2 is quenchable to room temperature at high pressures. Annealing of the high pressure phases at 1 bar and 300°C yielded the starting mixtures of AgInSe 2 with chalcopyrite structure and AgSbSe 2 or AgBiSe 2 , rsp. At 1 bar, 25°C the high pressure phases could be stored for at least 8 months.

Hochdruckreaktionen von Oxometallaten, VI: Hochdrucksynthese gemischtvalenter verbindungen VO2−δ (OH)δ mit CaCl2-struktur

Abstract Mixed valence compounds VO 2− δ (OH) δ (0.13 δ 4 VO 3 , at p > 20 kbar and T = 700–800°C. The blue-black substances crystallize orthorhombic, space group Pnnm. Single crystal data for VO 1.7 (OH) 0.3 ( a = 4.5113(7) A , b = 4.6303(8) A , c = 2.8652(5) A ) confirmed the structure to be CaCl 2 type, a distorted variant of the rutile structure. On heating in air to about 250°C, VO 2− δ (OH) δ is oxidized to VO 2 , which can conveniently be prepared from NH 4 VO 3 in this way.

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

Abstract K 3 V(VO 4 ) 2 with glaserite type structure was synthesized from KVO 3 in a modified Belt-type apparatus at 35 kbar and 800°C. The compound is the first glaserite-like phase with tetrahedral (VO 4 ) 3− -anions and V 3+ in octahedral coordination.

Arene–Arene Stacking in cis-Bis[2-(2-thienyl-C3)pyridine-N]platinum(II)

In the crystal structure of the title complex, [Pt(C9H6NS)2], although the aromatic ligands are coordinated to a central heavy metal atom, T-shaped and shifted π-stacked arrangements of the aromatic moieties are preferred, leading to a sandwich herring-bone type of crystal-packing motif. The crystal structure is therefore consistent with the view that the arene–arene interactions are determined by electrostatics (multipole–multipole).

The vibrational spectra of NbBO4, TaBO4, NaNb3O8 and NaTa3O8

Abstract The infrared and Raman spectra of NbBO 4 have been interpreted in terms of the zircon structure in space group I 4 1 / amd ( D 17 4 h ). Frequency shifts were observed in the Raman bands upon isotopic substitution of the boron atoms and when Nb was replaced by Ta in the crystal lattice. NaTa 3 O 8 contains TaO 8 dodecahedra which are almost identical to the ones in TaBO 4 and its Raman spectra are compared with those of NaNb 3 O 8 and of NbBO 4 amd TaBO 4 in order to assign metal—oxygen bands. The BO 5− 4 vibrational bands resemble those of the SiO 4− 4 groups rather than the B(OH) − 4 ones. However, the BO stretching force constant is much lower than the corresponding SiO one in SiO 4− 4 and it appears as if the metal—oxygen interactions are much stronger in NbBO 4 and TaBO 4 than in ZrSiO 4 and HfSiO 4 , respectively.

The vibrational spectra of the copper(II) formates: Part IV. The thermal behaviour of Cu(HCOO)2 · 4H2O and Cu(HCOO)2 · 2H2O

Abstract Several modifications of Cu(HCOO) 2 exist and two, or possibly three, are characterized in the present study by means of Raman measurements. Upon the dehydration of Cu(HCOO) 2 · 4H 2 O, monoclinic Cu(HCOO) 2 is formed in a topotactical reaction and a Raman study reveals that the environments around the copper and formate ions are very similar in the two compounds. No evidence can be found of the formation of the dihydrate by means of the dehydration of the tetrahydrate, even though DTA/TG measurements show that the dehydration process is complex and occurs in several steps. When monoclinic Cu(HCOO) 2 is further heated it transforms into orthorhombic Cu(HCOO) 2 below 100°C. The dehydration of the dihydrate results in the formation of a modification of Cu(HCOO) 2 which closely resembles the monoclinic modification but behaves differently upon further application of heat.

Pressure - temperature relations in the silver - tellurium system at 75 at-% tellurium

Abstract The p,T-relations in the silver-tellurium system at 75 at-% Te were studied by high pressure DTA and quenching experiments at pressures up to 3.2 GPa. Fitted data for the phase boundaries are given. AgTe 3 becomes a stable phase in the system above 0.4 GPa. In quenching melts with a nominal composition AgTe 3 from high temperatures, stable and metastable equilibria can be observed. Conditions for the formation of homogeneous AgTe 3 from the melts in the low-pressure region are discussed.

A Raman spectroscopic determination of the decomposition kinetics of ammonium metavanadate, NH4VO3

Raman spectroscopy was used to follow the kinetics of the thermal decomposition of solid ammonium metavanadate, NH4VO3. This method avoids the disadvantages of mass-loss determinations because it monitors directly the amount of reactant present. Time-dependent isothermal measurements of the intensity of the v (VO2)s band at 927 cm−1 have been made between 423 and 443 K. The reaction is deceleratory throughout. Applying the ln-ln method, derived from a generalized Avrami-Erofeev equation, to the experimental data, a value of n = 0.9 was found, i.e. a situation similar to first-order kinetics. An activation energy of EA = 48.6 kJ mole−1 has been calculated for the decomposition process.