Diatom frustules were used as bio-templates to synthesize functional ceramics via solid-gas displacement reactions. Silica based frustules were exposed to TiF₄ at 330°C to form TiOF₂ which is later converted to TiO₂ (anatase) by heat treatment in air at 600°C. The TiO₂ frustules were then exposed to Ba(OH)₂ at 120°C or Sr(OH)₂ at 160°C to form BaTiO₃ or SrTiO₃ respectively. Chemical composition, structure, and morphology of the converted frustules were studied by XRD, TEM, SEM, EDS. In both cases near complete conversion was achieved while retaining the morphology of the original silica frustules. Conversion of diatom frustules to Nb₂O₅ by solid-gas displacement reaction was also studied. Silica based frustules were exposed to NbF₅ vapors at 330°C which formed niobium oxy-fluoride (NbO₂F) intermediate. Oxygenation of the intermediate was attempted in oxygen atmosphere at high temperatures which resulted in formation of Nb₃O--F along with various off-stoichiometric niobium oxides. Conversion to Nb₂O₅ and its derivatives accompanied by evolution of NbOF₃ which compromised the shape of the original frustules
