Citric acid auto-combustion synthesis of Ti-containing perovskites via aqueous precursors

Mixed metal oxides find many established industrial as well as future applications, such as in thermochemical processes, catalysis, or the semiconductor and ceramics industries. These oxides can be prepared via direct solid state synthesis from the oxides, or via solution-based methods such as citric acid auto-combustion routes which involve nitrates as starting materials. However, especially in the case of titanates, direct solid state methods often yield low phase purity, and synthesis from nitrates cannot be carried out as stable titanium nitrates do not exist. We found that the dissolution of titanium monoxide (TiO) using hydrogen peroxide in the presence of ammonia yields an excellent aqueous precursor for citric acid auto-combustion which is insensitive towards hydrolysis. Moreover, the method is fast, easy to implement, and yields excellent phase purity. Solid solutions of CaMnO3 and CaTiO3 could be formed in any mixture ratio.