This work has as main objective physical and mechanical properties comparison of sintered silicon nitride sintered with rare earth concentrate-aluminum nitride and yttrium oxide-aluminum nitride as sintering aids. The sintering process has been performed using pressureless. The use of rare earth concentrate as additive during silicon nitride sintering gives rise to materials with similar physical and mechanical properties characteristics in relation to yttrium oxide-added silicon nitride. The hardness, fracture toughness and density from both materials, at room temperature, showed quite small differences. Therefore, the use of rare earth concentrate additives and pressureless sintering showed that there are low cost and good performance alternatives for precursors of silicon nitride at room temperature during sintering and densification.