Synthesis and features of binary cobaltite spinels

The main developments in the synthesis of cobaltites are surveyed. Solid state reactions between oxides, thermal decomposition of mechanical mixtures of transition metal salts, the use of complex compounds as precursors, mechanochemical synthesis, deposition of cobaltites on supports and cobaltite synthesis by thermal treatment of coprecipitated compounds are discussed and the specific advantages and disadvantages of each method pointed out. The binary spinel cobaltites find applications as materials in many fields, their main importance being as catalysts. In order to achieve high specific surface area, cobaltite synthesis by thermal treatment of coprecipitated precursors proves to be the most promising method. Different kinds of precursors are regarded. Transition metal basic salts are promising for the synthesis of binary mixed oxides and, in particular, of cobaltites. The conditions suited by the coprecipitated precursors for the synthesis of cobaltites with preset properties, such as high-dispersity, homogeneity, a definite stoichiometry and a low impurity content, are indicated. Special attention is paid to hydroxidecarbonates. Their use as precursors ensures these demands for the final product and also evolution of toxic gases during the thermal decomposition is avoided.