Synthesis and properties of the double perovskites La2NiVO6, La2CoVO6, and La2CoTiO6

The double perovskites La₂CoVO₆, La₂CoTiO₆, and La₂NiVO₆, are described. Rietveld fitting of neutron and powder X-ray diffraction data show La₂NiVO₆ and La₂CoVO₆ to have a disordered arrangement of B-cations whereas La₂CoTiO₆ shows ordering of the B-cations (with ∼5% Co/Ti inversion). Curie-Weiss fits to the linear region of the 1/χ plots reveal Weiss temperatures of −107, −34.8, and 16.3 K for La₂CoVO₆, La₂CoTiO₆, and La₂NiVO₆, respectively, and magnetic transitions are observed. La₂CoTiO₆ prepared by our method differs from material prepared by lower-temperature routes. A simple antiferromagnetic spin model is consistent with the data for La₂CoTiO₆. These compounds are semiconductors with bandgaps of 0.41 (La₂CoVO₆), 1.02 (La₂CoTiO₆) and 0.45 eV (La₂NiVO₆).     

Correction to: Differences in the Efficiency of Separation of Analgesic Drugs by High-Performance Thin-Layer Chromatography with Similar Octadecyl Silica-Based Adsorbents

JPC – Journal of Planar Chromatography – Modern TLC -     

Bismuth germanate and bismuth silicate glasses in cryogenic detectors

We present and discuss the results of measurements of conductivity and secondary electron emission coefficient of Bi_xGe_1−xO_2−0.5x (where x=0.13, 0.23, 0.33, 0.47) and Bi_xSi_1−xO_2−0.5x (where x=0.47, 0.57, 0.67) glasses reduced in hydrogen. The surface conductivity of reduced glasses strongly depends on reduction temperature, reduction time and bismuth content. The temperature dependence of the surface conductivity in a high temperature regime is well described by σ∼exp[−(T₀/T)ⁿ] law where n=1/4. The secondary electron emission coefficient of reduced glasses is practically independent of the degree of reduction but increases when binary glasses are modified by alkali ions. The research results confirmed that bismuth silicate and bismuth germanate glasses modified by alkali ions may be good materials for detectors working in cryogenic temperature.     

Differences in the Efficiency of Separation of Analgesic Drugs by High-Performance Thin-Layer Chromatography with Similar Octadecyl Silica-Based Adsorbents

JPC – Journal of Planar Chromatography – Modern TLC -     

Die Dehnviskosität des Polypropylens

Zusammenfassung Es wurden die Dehnviskositäten von Polypropylen-Schmelzen bei 180°C im Dehngeschwindigkeitsbereich 0,02 bis 1,0 s^–1 gemessen. Dabei wurden Proben von drei verschiedenen Herstellern und mit sehr verschiedenen Molmassen untersucht. Sämtliche Proben zeigten einen monotonen Anstieg der Dehnviskosität mit der Zeit. Die durch Extrapolation gewonnenen Gleichgewichts-Dehnviskositäten betrugen in allen Fällen das Dreifache der Null-Scherviskositäten. In keinem einzigen Fall konnte eine Dehnverfestigung der Schmelzen beobachtet werden. Nur bei unvollständig aufgeschmolzenen Proben (168°C Meßtemperatur) ergab sich der triviale Fall einer Dehnverfestigung als Folge der Dehnkristallisation. Kontrollmessungen an verzweigtem Polyethylen (bei 150°C) ergaben die erwartete Dehnverfestigung, während diese, ebenfalls erwartet, bei linearem Polyethylen ausblieb.

---

The elongational viscosities of polypropylene melts were measured at 180°C with different elongation rates between 0.02 and 1.0 s^–1 respectively. Samples were studied from three different manufacturers and some having markedly different molecular masses. All samples showed a monotonic rise of the elongational viscosity with time. The extrapolated steady-state elongational viscosities were always three times the values of the corresponding zero-shear viscosities. In no case strain hardening could be observed. Only incompletely molten samples (temperature of measurement 168°C) showed a kind of strain hardening as a consequence of strain crystallization. Control measurements with branced polyethylene at 150°C showed the expected strain hardening while this, also expected, was not observed in the case of linear polyethylene.

Herrn Professor Dr. Rolf Sammet zum 65. Geburtstag gewidmet     

Structure and electric conductivity of reduced lead–germanate,bismuth–germanate and bismuth–silicate glasses modified with potassium

Lead–germanate, bismuth–germanate and bismuth–silicate glasses, as potential materials for detectors production, have been modified with potassium with the purpose of improvement of mechanical properties. Studies on the influence of potassium modification on the structure and electric properties have been conducted with AFM, DSC and conductivity measurements. It has been observed that potassium modification improves the mechanical and technological properties of glasses and simultaneously changes slightly their electric properties. The studies have confirmed that bismuth–silicate and bismuth–germanate glasses are good materials for microchannel plates or channeltrons.