以溶膠-凝膠法製備鋰鋁矽玻璃陶瓷：微觀結構發展及物理特性探討

Abstract

本研究嘗試以 Sol-Gel 的化學方法製備 Li2O - Al2O3 - 7SiO2 系玻璃 陶瓷。為了探討成核劑對結晶相的影響，同時製備添加核成長劑 ZrO2 與 TiO2 的系統。系統中的所有成分都來自各元素的烴氧化物。首先透過 Sol-Gel 的途徑製備高純度、高均質性與超細的非晶相粉末，經過 DTA 的結晶成長動力研究，得知 ZrO2 可有效促進結晶。將粉體壓製成生胚， 以 XRD 鑑定經過不同溫度下燒結的試片，獲知 1000℃ 以上的主結晶相 為 beta-spodumene 固溶體。此晶相具極低的熱膨脹係數。CLAS 粉體與 CLAST 粉體的 Avrami 常數約為 3，顯示二者的結晶機構均為均勻且大量 的粉體表面成核引致的結晶。CLASZ 的 Avrami 常數約為 4，除前述之機 構外，另有因 ZrO2 大量析出引致異質成核之因素。所以添加 ZrO2 的粉 體比添加 TiO2 的更能有效成核，並因此降低結晶活化能。 Li2O-Al2O3-7SiO2 powders with or without nucleating agents, ZrO2 and TiO2, were prepared through the sol-gel process. Startingmaterials used are the alkoxides of the constituent elements, i.e., Li, Al, Si, Zr, and Ti. Highly pure and homogeneous fine powders thus obtained would be examined by DTA, and then subjected topressureless sintering at various temperatures in air. Glass-ceramics with very low or near-zero coefficients of thermal expansion could be obtained through a controlled crystallization process. The microstructural evolution of Li2O-Al2O3-SiO2 glass-ceramics was thoroughly investigated by XRD. The main phase was b-spodumene solid solution. The Avrami constants of the LAS specimen without nucleatiing agent or the LAS specimen with TiO2 are 3, showing a mechanism of volume crystallization is predominant. Because ZrO2 could easily precipitate inside the LAS system, the LAS containing the ZrO2 additives has more nucleation sites than others, the Avrami constant being equal to 4. It indicates that ZrO2 is an effective nucleating agent compared toTiO2.