Formation and Stability of β‐Quartz Solid‐Solution Phase in the Li‐Si‐Al‐O‐N System

Abstract

The development of crystalline phases in lithium oxynitride glass‐ceramics was examined, with particular emphasis placed on the effect of the nitrogen source (AlN or Si3N4) on the formation and stability of a β‐quartz solid‐solution (ss) phase. Oxynitride glasses derived from the Li‐Si‐Al‐O‐N system were heat‐treated at temperatures up to 1200°C to yield glass‐ceramics in which β‐quartz(ss) and β‐spodumene(ss) of approximate composition Li2OAl2O34SiO2 formed as major phases and in which X‐phase (Si3Al6O12N2) and silicon oxynitride (Si2N2O) were present as minor phases. The nitrogen‐containing β‐quartz(ss) phase that was prepared with AlN was stable at 1200°C; however, the use of Si3N4 as the nitrogen source was significantly less effective in promoting such thermal stabilization. Lattice parameter measurements revealed that AlN and Si3N4 had different effects on the crystalline structures, and it was proposed that the enhanced thermal stability of the β‐quartz(ss) phase that was prepared with AlN was due to both the replacement of oxygen by nitrogen and the positioning of excess Al3+ ions into interstitial sites within the β‐quartz(ss) crystal lattice.