Silicon nitride powder synthesis, performed by silicon tetrachloride ammonolysis, is described in this work. Gaseous ammonia reacts with liquid SiCl4, at low temperature and inert atmosphere. At a second step, a powder pyrolysis of silicon diimide is performed between 1300 and 1500degreesC, for ammonium chloride removal and Si3N4 formation. Phase formation is evaluated by X ray diffraction. Particle medium size and form is determined by Scanning Electron Microscopy.