Conversion of SiO 2 Diatom Frustules to BaTiO 3 and SrTiO 3

Diatom frustules were used as bio‐templates to synthesize functional ceramics via solid–gas displacement reactions. Silica‐based frustules were exposed to TiF 4 at 330°C to form TiOF 2 , which was later converted to TiO 2 (anatase) by heat treatment in air at 600°C. The TiO 2 frustules were then exposed to molten Ba(OH) 2 or Sr(OH) 2 to form BaTiO 3 or SrTiO 3 , respectively. In both cases, near‐complete conversion was achieved while retaining the morphology of the original silica frustules. BaTiO 3 and SrTiO 3 frustules exhibit nearly phase pure, nanocrystalline perovskite structure.