Carbon combustion synthesis of nanostructured perovskites

A novel, economical, and energy-efficient process to produce nanostructured particles of several perovskite oxides, such as ferroelectrics BaTiO₃, SrTiO₃ and LiNbO₃, is described. This process, referred to as carbon combustion synthesis of oxides (CCSO) is a modified SHS process that uses carbon as a fuel instead of a pure metal. In CCSO of nanostructured materials, the exothermic oxidation of carbon nanoparticles (∼5 nm) with a surface area of 80 m²/g generates a thermal reaction wave with temperature of up to 1200°C that propagates through the solid submicron reactant mixture, converting it to the desired complex oxide product. The carbon is not incorporated in the solid product since it is released in a gaseous form (CO₂) from the sample. The quenching front method combined with XRD and Raman spectroscopy revealed that crystalline tetragonal BaTiO₃ particles formed in the early stage of the combustion, before the temperature reached its maximum. A major difference between the thermal transport processes during CCSO and conventional SHS is the extensive emission of CO₂. The release of CO₂ enables synthesis of highly porous (up to 70%) powders having a particle size in the range of 60–80 nm with a surface area of up to 12.4 m²/g.