Abstract: The in situ controlled crystallizing process of Si-Al-Zr-O(SAZ) amorphous bulk was investigated by DSC, XRD, SEM and TEM techniques. The amorphous undergoes structural changes by treating at different temperatures. Phase segregation occurs at about 900℃, resulting in the formation of Si-rich and Al, Zr-rich regions. The t-ZrO2 is crystallized from the Al, Zr-rich region at 920--950℃ followed by poorly defined Al-Si spinel. With the increase of temperature up to 1000℃, mullite forms by reaction between Al-Si spinel and amorphous silica. The main crystalline phases identified are t-ZrO₂, mullite and some cristobalite with the spinel disappearing above 1000℃.

Key words: SAZ amorphous, phase development, microstructure change