Glass-ceramic with preferred orientation of Li2Si205 crystals produced by extrusion below crystallization temperature and subsequent heat treatment

Abstract

Glass-ceramics with oriented crystals have been produced from a lithium disilicate glass system by extruding the nucleated glass below the crystallization temperature, and subsequent heat treatment to achieve high-crystalline glass-ceramics. The extruded glass was found to possess a small amount of ahgned, elongated lithium disilicate crystallites and anisotropic stresses. The resulting glassceramic shows a high orientation of the needle-shaped Li₂Si₂O₅ crystals with their c-axis parallel to the extrusion direction. The degree of crystallographic orientation was found to be decreased for samples with an additional heat treatment slightly above Tg, placed between the extrusion process and the crystallization. The crystal alignment of specimens extruded below crystallization temperature is significantly higher than the alignment o f extruded glass-ceramic.