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

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 300-450 MPa. Crystallized samples were immersed in KNO3 molten salt, at temperatures of 400-420 degrees C for 9 or 16 h. 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. (c) 2015 Elsevier B.V. All rights reserved.