EFFECT OF HEAT TREATMENT SCHEDULES ON THE CRYSTALLIZATION BEHAVIOR AND THERMAL EXPANSION OF A LITHIUM DISILICATE BASED GLASS-CERAMIC

摘要

In this study, the crystallization behavior and thermal expansion coefficient of a lithium disilicate (LS2) based glass-ceramic derived from SiO_2-LiO_2-Al_2O_3-K_2O-ZrO_2 system was investigated by using x-ray diffraction (XRD), high temperature x-ray diffraction (HTXRD), differential thermal analysis (DTA) and dilatometer techniques. Analytical reagent grade chemicals were chosen as raw materials for preparing glass batches. Nucleation and crystal growth heat treatments were planned according to DTA results. The amounts of the amorphous and crystalline phases developed during the heat treatments were determined by quantitative XRD. XRD results of crystallized samples showed simultaneous formation of lithium silicate (LS) and quartz in the early stage of the crystallization followed by formation of lithium disilicate (LS2) at higher temperatures. The thermal expansion coefficients of glass ceramics were also measured depending on the applied heat treatments.