Compositional design for SrTiO₃ crystal precipitation from spinodal-type borosilicate glass containing large amounts of TiO₂

Abstract

B 2 OSiO 2 borosilicate glasses in a specific composition range show a spinodal-type phase separation by heattreatment at around those glass transition temperatures, and porous glasses or porous glass-ceramics can be easily obtained via an acid treatment after the phase separation. We have studied preparation conditions of SrTiO 3 -precipitated porous glass-ceramics for a photocatalyst of hydrogen generation using solar energy. It was found that the SrTiO 3 crystal was observed for a SrOBaOTiO 2 SiO 2 glass, while the SrTiO 3 crystal disappeared from SrOTiO 2 B 2 O 3 SiO 2 glasses, which contain the B 2 O 3 component necessary for the phase separation. For this problem, we found that co-doping of K 2 O and Al 2 O 3 components is effective, and a SrTiO 3 containing porous glass-ceramic was successfully obtained by the co-doping. Molecular dynamics (MD) simulations were performed to understand the migration of Sr 2+ ions in SrOTiO 2 B 2 O 3 SiO 2 glasses with K 2 O and Al 2 O 3 components. This paper is the first to describe the dynamics of alkali metal/alkaline earth metal ions in those glasses and the mechanism of SrTiO 3 precipitation in borosilicate glasses.