Synthesis and pyrolysis of polyborosilazane with low oxygen content

Polyborosilazane with a low oxygen content was synthesized by reacting perhydrosilazane with tris (dimethylamino) borane. The chemical structure of this polymer was investigated by infrared and nuclear magnetic resonance spectroscopies. The borazine ring structure was observed in the polymer. Amorphous silicon nitride was obtained by pyrolysis of this polymer in a stream of N sub 2 at 1000 deg C with approx80 mass% ceramic yield. The pyrolysis product remained amorphous after further heating to 1700 deg C < N sub 2 . The oxygen content in the pyrolysis product was 1.1 mass%. Crystallization to beta -Si sub 3 N sub 4 , beta -SiC and alpha -Si sub 3 N sub 4 took place on annealing in N sub 2 at 1800 deg C for 1 h. These results indicate that this polyborosilazane is a good precursor for amorphous silicon nitride-based materials with low oxygen content.