Si3N4-MgO-Y2O3 ceramic materials have been fabricated by pressureless sintering, which overcomes the limitations of hot pressing. The amount Of Y2O3 has a strong influence on the densification behavior and mechanical properties of the sintered materials. The pressureless sintered silicon nitride with 5 wt.% MgO + 4 wt.% Y2O3 achieved a relative density of 99%, a bending strength of 950 MPa and a fracture toughness of 7.5 MPa m(-1/2). (C) 2004 Published by Elsevier B.V.