Microstructural Development of Calcium alpha‐SiAlON Ceramics with Elongated Grains

Abstract

Silicon nitride (Si 3 N 4 ) and SiAlONs can be self‐toughened through the growth of elongated β‐Si 3 N 4 /β‐SiAlON grains in sintering. α‐SiAlONs usually retain an equiaxed grain morphology and have a higher hardness but lower toughness than β‐SiAlONs. The present work has demonstrated that elongated alpha‐SiAlON grains can also be developed through pressureless sintering. alpha‐SiAlONs with high‐aspect‐ratio grains in the calcium SiAlON system have exhibited significant grain debonding and pull‐out effects during fracture, which offers promise for in‐situ ‐toughened α‐SiAlON ceramics.