Pressureless sintering of hexagonal boron nitride powders

Pressureless sintering of hexagonal boron nitride (BN) with and without additives was performed using a powder which was previously nitrided at 900 degrees C and then heat treated at 1400 degrees C. Sintering additives were B2O3 (2, 4, 6 wt %) and Y2O3 (2, 4, 6 wt %) and sintering temperatures was 1900 degrees C. Sintered samples were characterized by XRD, SEM, micro hardness, density and mercury porosimeter measurements. Maximum density values of samples were 1.56 g/cm(3) without additives and 1.63 g/cm(3) with additives. Hardness values of samples were found to improve with the presence of additives.