[Study of Raman and IR spectra for Si-Al-Zr-O amorphous bulk in-situ crystallization]

The structural changes in the in-situ controlled crystallizing process of Si-Al-Zr-O(SAZ) amorphous bulk were investigated by laser Raman (LRa), infrared (IR) and X-ray diffraction (XRD) techniques. The structure of the amorphous network apparently reorganized at about 920 degrees C, resulting in the formation of Si-rich and Al, Zr-rich regions. The t-ZrO2 was crystallized from the Zr-rich region at 920-950 degrees C and poorly defined Al-Si spinel was formed from the Al-rich regions. With the increase in temperature, the peak of Al-Si spinel was enhanced and then disappeared in the XRD pattern, and the characteristic IR band groups of mullite centered in the 1 200-1 100, 1 000-700 and 650-400 cm(-1) could be observed. At 1 100-1 150 degrees C, the Raman bands at 179 and 193 cm(-1) typical for the m-ZrO2 occurred and cristobalite was detected, and the main crystalline phases were identified as t-ZrO2 and mullite. These results indicated that mullite was formed by reaction between amorphous silica and the Al-Si spinel which was metastable phase. During the heating process, t-ZrO2 was crystallized firstly and a portion was transformed to m-ZrO2 at high temperature, and the left amorphous silica was transformed to cristobalite.