Effect of long-term heating and thermal cycling on thermal expansion, phase distribution, and microhardness of lithium aluminosilicate glass-ceramics

Lithium aluminosilicate glass-ceramics prepared by two different devitrification procedures were subjected to thermal cycling and heat treatment at 700 and 800 °C for up to 16 days in air. Changes in microstructure, phase distribution, microhardness, and thermal expansion behavior were monitored. Glass-ceramics prepared with a 950 °C nucleation step were observed to have various advantages over those prepared with a 1000 °C nucleation treatment. These advantages include finer microstructure, higher microhardness, and an almost linear thermal expansion behavior in the as-devitrified state. Additionally, no significant changes in physical properties were detected in the 950 °C-devitrified samples, while 1000 °C-devitrified glass-ceramics were found to be thermally unstable, causing important property changes, jeopardizing their reliability.