Extensive analysis of the formation mechanism of BaSnO3 by solid-state reaction between BaCO3 and SnO2

In this paper, the phase evolution, microstructure changes, and element diffusion for the formation of BaSnO3 from BaCO3 and SnO2 were extensively investigated. It was found that BaCO3 rapidly diffused on surface of SnO2 at the initial stage of the reaction (approximately 700 °C), forming a uniform BaSnO3 shell. Subsequently, BaSnO3 grew via two different routes depending on the calcination temperature. When the reaction was carried out below 820 °C, BaSnO3 phase further grew by diffusion of barium ions across BaSnO3 layer to SnO2 phase, since the BaSnO3 interlayer prevented the direct reaction between surface BaCO3 and SnO2 core. Once a higher temperature above 820 °C was provided, Ba2SnO4 were generated by reaction between BaCO3 and BaSnO3 shell. Under such circumstances, pure BaSnO3 was obtained by diffusion of barium ions from Ba2SnO4 across BaSnO3 to SnO2. The rate-determining step in both cases was assigned to the diffusion of barium ions.