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[en] X-ray diffraction studies on solution-grown LiKSO₄ have been performed between 70 K and 300 K. The lattice parameters have been obtained as a function of the temperature. The hexagonal to trigonal phase transition at 205 K is seen by a slight increase of the c lattice parameter, while the ferroelastic transition at 182 K is accompanied by the appearance of an important spontaneous elastic deformation. The deformation and the domain pattern are analysed via a 'squeezing' model of the hexagonal lattice which leads to a monoclinic lattice below T_c = 182 K. (authors)

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[en] Short communication

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[en] We report the production of single-wall carbon nanotubes (SWNTs) using a continuous wave (cw) 10.6 μm CO₂-laser. A wide range of experimental parameters and their influence on the formation of SWNTs has been investigated. It turns out that the temperature environment near the zone of evaporation plays a key role in the growth process of SWNTs. This result has important consequences for the optimization of the production of SWNTs

[en] LiK_1-xRb_xSO₄ (x≤0.50) mixed crystals have been investigated by neutron powder thermodiffractometry. The temperature evolutions of the lattice parameters of the crystals x=0.10, 0.20 and 0.50 are presented for the first time, in the temperature range 320 to 800 K. The main effects produced by the random substitution of the rubidium ions in the potassium sites are the variations of the critical temperatures and the smearing of the first order transitions presented by these compounds. A qualitative model based upon lattice parameter and steric repulsion changes is proposed to explain our results. The temperature variations of the c/a ratio show characteristic behaviours for each phase, being almost independent of the particular rubidium concentration. (author)

[en] A new cationic silver N-alkylpyridylporphyrin complex is able to ‘sense’ nanometric conductive particles with a diameter below 10 nm. The luminescence of the molecule changes its maximum from red to blue when it embraces a conductive (metallic or semiconducting) nanoparticle. The change is explained on the basis of a charge transfer between the molecule and the conductive nanoparticle along with a geometrical distortion of the porphyric ring and pyridinium substituents. This new molecule could be used to sense nanoparticle contamination in the environment, in the industry of heterogeneous catalysis and many other branches of nanometrological applications. (paper)

[en] We have performed polarized Raman scattering measurements on several Czochralski-grown lanthanide trifluoride (LnF₃) crystals presenting the β-YF₃ structure (space group: Pnma). The phonon mode assignments for the DyF₃ and LuF₃ spectra are given for the first time. Besides this, the Raman spectra of TbF₃, ErF₃ and YbF₃ complete and extend previous studies on these materials. The vibrational modes of LnF₃ compounds are then correlated with those of the archetype β-YF₃ crystal. The totally symmetrical fundamentals present a strong dependence on the scattering geometry, similar to what is shown by molecular crystals with weakly interacting molecules. Most of the Raman features are well behaved with the lanthanide ion substitution. Although the observed modes always involve all ions, it was possible to discern modes that are dominated by the motion of either the lanthanide or the fluorine ions. The intensity of some low frequency modes has proved to be quite dependent on the orthorhombic distortion of the quasi-hexagonal structure