Glass–ceramics of LAS (Li2O–Al2O3–SiO2) system enhanced by ion-exchange in KNO3 salt bath

Abstract

The paper describes a low-temperature ion-exchange process on specially designed Li2O–Al2O3–SiO2 glass–ceramics (LAS). Due to thermal treatment, two main crystalline phases: lithium di-silicate and lithium alumina-silicate were obtained in glass–ceramic materials. As a result of proper time/temperature profile treatment of precursor glasses, flexural strength of final materials increased up to 300–450MPa.Crystallized samples were immersed in KNO3 molten salt, at temperatures of 400–420°C for 9 or 16h. The final materials achieved almost 100% greater mechanical resistance than glass–ceramics before ion-exchange.We claim that the process of ion-exchange improved flexural strength significantly. Furthermore, it resulted in some changes of the surface layer structure. We noticed that chemical tempering process leads to decrystallization of the multiphase LAS glass–ceramic surface layer consisting of lithium di-silicate and lithium alumina-silicate phases.