Nanocomposite formation through thermal decomposition of mixed samarium and magnesium citrate-derived gels formed by spray pyrolysis

Abstract

Metal citrate gels of samarium and magnesium were used as precursors for the generation of hollow sphere particles by spray pyrolysis under mild thermal conditions. Six mixtures with different Sm/Mg ratios as well as pure Sm and Mg samples were prepared. As a result of the low synthesis temperature the particles consist of amorphous metal carboxylate networks. The texture of the shells is governed by microporosity yielding the major part of the total surface area. A detailed investigation of thermal decomposition, crystallization, and grain growth behavior was carried out under constant heating rate conditions. The decomposition products are nanocrystalline Sm2O3 and MgO and corresponding two-phase nanocomposites. The pure samarium carboxylate gel features considerably higher thermal stability compared with the one comprised of only magnesium. Accordingly the decomposition behavior of mixed samples is dependent on the Sm/Mg ratio. Furthermore it is shown that small amounts of MgO are able to slow down the kinetics of grain growth of Sm 2O3 whereas high amounts are necessary to significantly reduce the final grain size at 1000°C. © 2008 The American Ceramic Society.