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 BaSnO 3 from BaCO 3 and SnO 2 were extensively investigated. It was found that BaCO 3 rapidly diffused on surface of SnO 2 at the initial stage of the reaction (approximately 700   °C), forming a uniform BaSnO 3 shell. Subsequently, BaSnO 3 grew via two different routes depending on the calcination temperature. When the reaction was carried out below 820   °C, BaSnO 3 phase further grew by diffusion of barium ions across BaSnO 3 layer to SnO 2 phase, since the BaSnO 3 interlayer prevented the direct reaction between surface BaCO 3 and SnO 2 core. Once a higher temperature above 820   °C was provided, Ba 2 SnO 4 were generated by reaction between BaCO 3 and BaSnO 3 shell. Under such circumstances, pure BaSnO 3 was obtained by diffusion of barium ions from Ba 2 SnO 4 across BaSnO 3 to SnO 2 . The rate-determining step in both cases was assigned to the diffusion of barium ions.