Abstract
Rare-earth alkaline-earth mixed oxides containing transition metals (Mo, V) were prepared via pyrolysis in polymer–salt systems. The products were characterized by thermal analysis, resistance measurements, dilatometry, optical microscopy, and x-ray diffraction. The introduction of polyvinyl alcohol into the system containing lanthanum or strontium nitrate and ammonium molybdate was found to have a significant effect on the thermal decomposition process, testifying to changes in the bonding configurations of the constituent components in the systems studied, capable of forming stable gels, which are then used as precursors to synthesize oxide materials. The temperatures of different stages of dehydration were shown to be lower in the polymer-containing systems. The effect of solution acidity was assessed by examining thermal decomposition in systems containing a polymer and Mo or W salts and acidified with nitric acid. The reaction of nitrates (oxidants) with the polymer was accompanied by an exotherm at ≃170°C, corresponding to the melting of ammonium nitrate, resulting from an exchange reaction. The exothermic reaction was found to reduce the decomposition temperatures of the salts involved. The use of polymer–salt systems allowed the mixed oxides SrMoO4 and La2(MoO4)3 to be synthesized at lower temperatures in comparison with the coprecipitation of poorly soluble compounds. The method was also shown to be suitable for preparing perovskite oxides in the La1 – x Sr x Co1 – z M z O3 ± y (M = Mo, V) systems.
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Ostroushko, A.A., Mogil'nikov, Y.V. & Ostroushko, I.P. Synthesis of Molybdenum- and Vanadium-Containing Mixed Oxides in Polymer–Salt Systems. Inorganic Materials 36, 1256–1263 (2000). https://doi.org/10.1023/A:1026689816789
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DOI: https://doi.org/10.1023/A:1026689816789