Monolithic dried gels were synthesized by a sol-gel process from a mixture of Si (OC₂H₅) ₄, PO (OC₂H₅) ₃ and Ge (OC₂0₅) 4 solutions using N, N-dimethyl formamide as a drying-control chemical additive. Gelation of the solution was carried out at 60°C and the obtained wet gel was allowed to dry by making a pinhole on the closed container at 150°C. The monolithic dried gel could be converted into an amorphous, transparent and cylindrical rod without crack and bloating by heating to 900-1000°C. The change of bonding state of the dried gel was investigated by Fourier transforminfrared spectroscopy. The absorption band near 1320 cm^-1 is attributed to P=0 stretching mode. The band becomes stronger indicating an increase in the double bond character with increasing heat-treatment. It is suggested that the phosphorus component exists as a PO₄ tetrahedron in the amorphous SiO₂-P₂O₅-GeO₂. Specific surface area, average pore size and total pore volume of the gels were determined by BET method. The structure of the dried gel was porous including solvents, and the dense gel was obtained by heat-treatment. This was based on the viscous flow sintering, and it was indicated that it depended on P₂O₅ content.

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