Mechanochemical Synthesis of Nanocrystalline Complex Oxides

Abstract

The nanocrystalline complex oxides were produced by mechanochemical activation for high exothermal reactions of barium peroxide with metals (Ti, Zr, Mo, Al, Sn, Si, Fe). Mechanochemically synthesized complex oxides were studied by x-ray diffraction and by electronic microscopy methods. 1. Introduction The production of nanocrystalline powder complex oxides is one of main problems of modem technology of segneto-, piezo- and magnetic ceramics. The conventional technology of obtaining of ceramics on the basis of complex oxides is based on high-temperature synthesis from simple oxides or from their mixtures with carbonates. This diffusion limiting process requires high temperatures, high degree of dispersion of initial powders. The complex oxides obtained by this methods represent particles measuring 1-5 μm. Complex oxides may be produced by metallothermal method from peroxides (oxides) and metals [1], and by self-propagating high-temperature synthesis [2-6], however these processes are attended with high temperature in reaction zone. Temperature of combustion zone for reaction alkali earth metal with metal (titanium, zirconium, aluminium) ranges up to 2500-3000K [5], and size of particle in this case comprises 5-10 μm [6, 7]. One would expect that mechanochemical approach is useable for high exothermic synthesis complex oxides. It is known that constantly cooling drums of planetary ball mill allow to reduce the temperature at the reaction mixture, because the balls and reaction mix are in continuous contact with surface of constantly cooling drums [8]. It is hoped that the reduction of this temperature is able to change the size of particles at mechanochemical synthesis. The purpose of this work is mechanochemical synthesis of nanocrvstalline complex oxides for high exothermal systems.