Design Of New Oxide Ceramic Materials And Nanocomposites With Mixed Conductivity By Using Mechanical Activation Route.
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Design Of New Oxide Ceramic Materials And Nanocomposites With Mixed Conductivity By Using Mechanical Activation Route. Vladimir V. Zyryanov*, Nikolai F. Uvarov*, Vitalii G. Kostrovskii* Vladislav A. Sadykov**, Tatiana G. Kuznetsova**, V. A. Rogov**, V. I. Zaikovskii**, Y.V. Frolova**, G. M. Alikina***, G. S. Litvak**, E. B. Burgina**, E. M. Moroz**, S. Neophytides***. *- Inst. of Solid State Chemistry SB RAS, Novosibirsk, Russia; **- Boreskov Inst. Catalysis SB RAS, Novosibirsk, Russia; ***- Inst. Chem. Eng. & High Temperature Proc., Patras, Greece. ABSTRACT Some perovskite –like Fe (Co) -containing and fluorite-like Bi –containing solid solutions considered as promising materials for high oxygen flux membranes application have been synthesized by the mechanochemical activation route. Structural/microstructural features of those systems characterized by TEM, XRD, IR, and Raman spectroscopy are compared with the data on their mixed conductivity and oxygen mobility. Some properties of nanocomposites comprised of those materials and such oxides as Fe2O3, BaTiO3, BaBiO3 etc are elucidated as well. Densification of those powdered samples by sintering in the 7001400 K temperature range is accompanied by annealing of metastable phases generating “core-shell” nanocomposites with oxygen transport properties different from those of traditional materials. INTRODUCTION Conventional approaches for synthesis of ceramic nanopowders (including mixed conductivity complex oxides for membrane application [1]) are sol-gel method, coprecipitation, polymerized complex precursor route (Pechini method [2]) etc. Mechanochemical approach (high energy ball milling, MA) appears to be an attractive alternative to those methods since it is more reproducible, efficient, fast, and allows to easily produce nanocomposites and metastable compounds with unique properties [3-5]. Membranes made of nanosize grain ceramics/nanocomposites are expected to have better mechanical properties due to superplasticity [6] as well as a higher conductivity due to increased interface/bulk ratio [7]. This work presents results for MA synthesis of some complex oxides with perovskite-like and fluorite-like structures and characterization of their properties as related to possible application for the oxygen separating membranes. For comparison, samples of Bi1.5Y0.3Sm0.2O3 system were prepared by citrate and Pechini routes and studied as well. EXPERIMENTAL Complex oxides in Sr-Ba-Fe-Co-O system were prepared by 5 min mechanical milling of the starting reagents (SrCO3, BaCO3, Fe2O3, CoO) blends in AGO-2 planetary mill with the powder/steel ball ratio ~12/200 followed by calcination at 1000°C÷1100°C. To decrease drastically the iron contamination and increase the activated mixture homogeneity, a proprietary procedure of the MA treatment was used [8]. The milling and firing procedures were repeated for 3 times, and finally a ceramic powder was milled for 10 min. Bi containing complex oxides were obtained by MA synthesis in identical conditions with annealing at 100
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