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

Abstract

Lithium aluminosilicate glass-ceramics prepared by two different devitrification procedures were subjected to thermal cycling and heat treatment at 700 and 800degreesC for up to 16 days in air. Changes in microstructure, phase distribution, microhardness, and thermal expansion behavior were monitored. Glass-ceramics prepared with a 950degreesC nucleation step were observed to have various advantages over those prepared with a 1000degreesC 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 950degreesC-devitrified samples, while 1000degreesC-devitrified glass-ceramics were found to be thermally unstable, causing important property changes, jeopardizing their reliability. (C) 2003 Elsevier B.N. All rights reserved.