Glass development and controlled crystallization in the SiO₂ - Li₂O - ZrO₂ - P₂O₅ System

Abstract

The objective of this investigation was to analyze glass formation and crystaUization in t h e SiO₂ - Li₂O- ZrO₂ - P₂O₅ System for the development of high-strength glass-ceramics produced with glass powder. In the course of this study, it was found that the base glass or the semicrystalline glass-ceramic could be pressed to form glass-ceramic final products. The analysis of glass formation demonstrated that in a relatively large composition range, up to almost 30 wt%, ZrO₂ could be incorporated into the base glass and increased the glass forming tendency. Other additives were also tested. The presence of ZrO₂ crystals, ZrSiO₄ crystals and lithium phosphate crystals as well as other secondary phases in t he microstructure following heat treatment at approximately 1000 °C was estabhshed in SEM and XRD examinations. This glass-ceramic possesses fiexural strengths of 280 MPa. Translucency was observed in 0.5 mm thick layers. Growth rates of the main crystal phases were determined with cast monolithic samples in a semiquantitative kinetic evaluation of phase development. In contrast to the kinetics of mica crystal growth processes in machinable glass-ceramics, no time lags were observed.