Preceramic polysilazane was added to high purity Si powders as a reactive binder during synthesis of reaction bonded Si3N4 parts to improve the defect structures in both the unfired and nitrided parts. This study examined how the presence of Si powder affected the polymer-to-ceramic transformation of the polysilazane. Pyrolysis of both polysilazane and polysilazane+Si samples were characterized by TGA. Also, the gaseous volatiles evolved during pyrolysis were characterized by infrared and mass spectrometry. Results show that between 100- 550°C, silicon powder inhibits the loss of silazane oligomers from the polysilazane. However, for temperatures above 550°C, the weight loss differences between the pure polysilazane and the polysilazane+Si samples were less pronounced. Specific solvents used in the preparation of the polysilazane+Si mixtures affected the quantity and type of species in the volatiles during pyrolysis.