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[en] Various types of metal oxides with the perovskite structure were synthesized. In the ABO₃ type with A = La and B = Co, Mn, part of the A-cations were substituted by Sr or Ce. A₂BO₄ oxides with A = La, B = Co were prepared as well and partially substituted by Sr. Finally, double perovskites were investigated. The catalytic effect of the oxides were tested for oxidation of hydrocarbons and CO and for the reduction of NO using automobile exhaust gas. The catalysts of the ABO₃-type showed the best activity

[en] The preparation of YBa₂Cu₃O_7-x high critical temperature superconducting thin films is reviewed. Thin films have been grown by many techniques, including sputtering, electron beam evaporation, laser ablation, spray pyrolysis, molecular-beam and epitaxy (MBE). Stoichiometric films with high T_c and J_c have been obtained using each of these methods. The choice of substrate significantly affects the superconducting properties, and among the numerous substrates studied MgO, ZrO,₂ and SrTiO₃ yield best results. This review outlines the various deposition techniques, the effect of postdeposition annealing and the subsequent film--substrate interactions

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[en] The rare earth oxysulfate series Ln²O²SO⁴ (Ln = La, Gd, Y) was synthesized by two different thermal decomposition methods. The complex ion (LnO)_nsup n+/) existing in the structure of various oxysalts seems to have a major effect on the appearance of the spectra. Then it is possible to derive sets of crystal field parameters simulating the spectra, by using the C_4v → C_2v descending symmetry procedure. Moreover, an alternative method for determining these parameters is described when a C_2v point site symmetry is distorted from D_3h

[en] Chalcogenides TiSe_1.60-xTe_x (0 ≤ x ≤ 1.60), forming a continuous series of hexagonal solid solutions, were prepared by the direct ampoule procedure. The thermal decomposition of TiSe_1.60-xTe_x was studied for the samples with x = 0, 0.16, 0.80, 1.44, and 1.60 in Ar and N₂ atmospheres in the course of heating from 25 to 1000 deg C. The selenide undergoes no weight loss under Ar, in contrast to the telluride which disproportionates and loses weight owing to the formation of volatile TiTe₂. At high temperatures, tellurides are more sensitive than selenides to the presence of nitrogen: the disproportionation is accompanied by the reaction of TiTe₂ with N₂, yielding low-volatile titanium nitride and free tellurium. Titanium selenide and telluride as components of the solid solutions behave similarly to the corresponding individual chalcogenides

[en] The oxygen contents in YBa₂Cu₄O_z samples have been determined by two wet chemical redox methods, i.e. by Coulometric and iodometric titrations. Three different samples, synthesized by sol-gel, LiF catalyst and O₂ hot-isostatic-press (HIP) techniques, are studied. The results of the two titration methods agree well with each other for all samples. The oxygen content z appears to be dependent on the oxygen pressure applied during the synthesis, since z values slightly below the stoichiometric number of 8.00 have been obtained for the samples prepared under 1 atm oxygen pressure, while for the O₂ HIP treated sample the observed oxygen content is Z=8.00±0.01. (author)

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[en] Bulk YBa₂(Cu_1-y⁵⁷Fe_y)₄O₈ samples with y=0.00-0.05 were synthesized by an aqueous sol-gel method under 1 atm oxygen pressure. The samples were characterized by XRD for phase purity and lattice parameters, by thermal analysis for oxygen stability as well as by magnetic susceptibility and SQUID measurements for magnetic and superconducting properties. Iron was found to both destabilize the YBa₂Cu₄O₈ phase and have a strong effect on its properties even at very low concentrations. The site assignment proposed for the iron dopant is based on the results of ⁵⁷Fe Mossbauer spectroscopy studies. The results are compared with the observed iron doping effects in the YBa₂Cu₃O_7-δ phase. (author)

No abstract available