The important features of silicon nitride (Si₃N₄) such as proper strength, low dielectric constant, low loss tangent and high wear and thermal shock resistance have made this ceramic as one of the few suitable ceramics for use in antenna protection. Due to the difficulties in the sintering of Si₃N₄ samples, in this research, the fabrication of this body was investigated by nitridating a pressed silicon powder without using any additive; because the effect of additives on the loss of properties has been proven. In this regard, silicon powder along with 0, 0.5, 0.7, and 1 wt.% of iron oxide were pressed, and nitridated at the temperature of 1420 degree celsius for 2 hours under the different nitrogen gas pressures of 200, 400, and 600 millibars. The density, porosity, phase composition, and microstructure of the samples were evaluated. Results showed that the minimum pressure for nitridation is 600 millibars and the optimal percentage of iron oxide is 0.5 wt.%.