A silicon diimide gel Si(NH)(x)(NH2)(y)(NMe2)(z) was prepared by an acid-catalyzed ammor olysis of tris(dimethylamino)silylamine. Pyrolysis of the gel at 1000 degreesC under NH; flow led to the formation of an amorphous silicon nitride material without carbon contamination. All of the gel and pyrolyzed products exhibited a mesoporous structure with a high surface area and narrow pore-size distribution. The effective surface area of the pyrolyzed silicon nitride residues decreases with increasing temperature, but the heating rate during pyrolysis has little influence on the surface area and pore-size distribution of the final mesoporous ceramic Si3N4 products because of the highly cross-linked structures of the precursor silicon diimide gel.