Silicon nitride (Si3N4) is a synthetic covalent compound, employed to manufacture high creep resistance bodies. There is a general agreement that pure Si3N4 is difficult to sinter by classical methods, thus alternative techniques have been proposed. One of them is the addition of certain sintering aids, leading to liquid-phase sintering process. For this research aluminum nitride (AIN) and a rare-earth carbonate were chosen as sintering aids. Test pieces were prepared from mixtures of these materials and pressureless sintered under a nitrogen-rich atmosphere. These pieces were tested by means of a compressive creep apparatus assembled at CTA/IAE/AMR.