­Effect of sintering treatment time on the sintering behaviour and thermal shock resistance of Li2O-Al2O3-SiO2 glass-ceramics

Abstract

ABSTRACT In order to determine the correlation of flexural strength and thermal shock resistance properties, the sintering behavior of Li2O-Al2O3-SiO2 (LAS) glass-ceramics at different sintering treatment times and the effect of thermal shock cycles on LAS glass-ceramics were investigated. The LAS glass-ceramics were isothermally treated at 1100°C from 1.5 to 4.5 h. Phase transformation of major crystalline of β-spodumene and minor crystalline of ZrTiO4 revealed unchanged as sintering treatment time increased. The physical properties of LAS glass-ceramics that were sintered for 3.5 h demonstrated an increased density (2.45 g/cm3) and less porosity percentage (0.62%). The prolonged sintering treatment affected the microstructure whereby the mean grain size increased from 0.55 to 0.67 µm which also demonstrated the increase of microhardness in the range between 3.90 and 5.47 GPa. The flexural strength of LAS glass-ceramics revealed an enhancement of 158 MPa when sintered for 3.5 h. The thermal shock resistance properties were assessed at 500°C from one to seven cycles via thermal shock tests. After four thermal shock cycles, LAS glass-ceramics showed an improvement of 82% of residual strength from its original strength, due to a decrease in the formation of pores and an increase in the crystallinity and percentage of β-spodumene.