Abstract:The pressureless sintering process of Sialon ceramics added (1.5% La₂O₃+4.5%Y₂O₃) as sintering aids was studied. It is found that a β′-Sialon with relative density over 99%is obtained by sintering at 1750℃ for 1h.  Crystal grain growth was observed at room temperature by SEM for the samples sintered at 1800℃ holding for different time. It is proved that grain growth along c-axis of β′-phase is a first priority, since (210) and (001)  lattice plans have different activation energy. On the present conditions, logarithm of grain aspect ratio L￣/W￣ of average grain length L￣ to average width W￣ is in proportion to sintering time because of proportion of lgL￣to sintering time and proportion of W￣ to sintering time.

Key words: Sialon; grain growth; pressureless sintering