Microwave-Assisted Combustion Synthesis of LaCrO_3 Nanopowders

摘要

Microwave-induced combustion synthesis (MICS) experiments have been conducted to obtain LaCrO_3 and La_(0.8)Ca_(0.2)Cr_(0.7)Co_(0.3)O_4 nanopowders using urea as fuel. The process is, in the simplest sense, the exploitation of an exothermic and usually very rapid chemical reaction. The microwave radiation provides volumetric and selective heating, where heat is generated within the reaction volume itself by the interaction of microwaves with the material. Control of ignition and reaction to yield nanoparticles can be accomplished with time-regulated microwave heating. At the present time LaCrO_3 perovskite-type and/or LaCrO_3 modified by various dopants like calcium and cobalt are the most suitable ceramics to fulfill all the required criteria to be used as interconnecting component in solid oxide fuel cells. Besides low electrical resistance, under fuel and oxidizing atmospheres, and chemical inertness, lanthanum chromite has a closely matched thermal expansion to the stabilized zirconia electrolyte. The as-prepared nanopowders products, characterized by XRD, SEM and BET, showed high specific surface area 12.9 and 12.0 m~2/g and have very small particle and crystalline size, with atomic level homogeneity of 57 and 27 nm, respectively. The results were compared to the results obtained from conventional combustion reaction and indicated that microwave assistance can permit the formation of LaCrO_3 and La_(0.8)Ca_(0.2)Cr_(0.7)Co_(0.3)O_4 nanopowders.