The use of 29Si NMR to characterize the sol-gel synthesis of cordierite

Cordierite powder was synthesized via different sol-gel procedures. The use of 29Si NMR spectra of all stages beginning from tetraethoxysilane (TEOS) up to final ceramic powder material is discussed. In the early stages of the sol-gel process all oligomeric structure units can be identified. Spectra of the higher condensed sols only allow the quantification of Qn-groups. MAS spectra of gels heated up to 750 °C show no fine structure to be evaluated. Spectra of samples heated to 1250 °C indicate a sluggish disorder-order transformation from hexagonal α-cordierite to orthorhombic cordierite.