Sintering ofβ-sialon with 5mol% Y2O3-ZrO2 additives

The sintering behaviour ofβ-Sialon composition powders with 5 mol% Y₂O₃-ZrO₂ additives at 1750°C for 1.5 h in nitrogen or argon atmospheres was studied.β-Sialon composition powders could be pressureless-sintered to about 93% theoretical density by the addition of 5 wt% 5 mol% Y₂O₃-ZrO₂. By HIPing the pressureless-sintered bodies the density was increased to higher than 98% theoretical density, and uniform submicrometre ZrO₂ particles were homogeneously dispersed in theβ-Sialon matrix, resulting in an increase of fracture toughness,K _1c, from 5.1 to about 5.7 MN m^−1.5. Increasing the amount of tetragonal ZrO₂ transformable to monoclinic phase in theβ-Sialon matrix increasedK _1c.