MICROSTRUCTURE AND PROPERTIES OF SPODUMENE BASED LI-SI-AL-O-N GLASS-CERAMICS

Glasses and glass ceramics in the Li-Si-Al-O-N system were prepared us ing a natural mineral resource, and the microstructures and mechanical and thermal properties examined. The dominant phases that formed in t he Li oxynitride glass ceramics were beta-quartz(ss) and beta-spodumen e(ss), and these were believed to develop with equiaxed and acicular g rain morphologies respectively. Silicon oxynitride Si2N2O and X-phase Si3Al6O12N2 formed as minor phases. Nanoindentation was used to assess the hardness and elastic moduli of the Li-Si-Al-O-N materials and bot h parameters were observed to increase with increasing nitrogen conten t. Thermal expansion measurements revealed that the low expansion char acteristics of mineral derived beta-quartz(ss) and beta-spodumene(ss) were generally retained when nitrogen was introduced into the Li2O-Al2 O3-SiO2 system. (C) 1997 The Institute of Materials.