Influence of single-side ion exchange parameters in LZS and LZSA sintered glass-ceramics

Abstract

During processing and use of glass and glass-ceramic products, defects are generated, compromising their mechanical strength and one of the methods applied to promote an increase in mechanical strength is the ion exchange. An ion (usually an alkaline with larger ionic radius) from an external source (usually a salt) replaces position with another alkaline ion (with smaller ionic radius) from material. This ion substitution produces residual compressive stress on materials surface, which can promotes an increasing in mechanical strength. In this context, sintered glass-ceramic from the systems Li2O–Zr2O–SiO2 (LZS) and Li2O–Zr2O–SiO2–Al2O3 (LZSA) were subjected to ion exchange by salt paste method using different sodium-lithium ratios, at temperatures 100°C below to the glass transition temperatures of the parent glasses, with 60–600min holding time. Despite the small amount of sodium obtained after ion exchange (0.30–0.80wt.%), the exchange layer verified in sintered LZS glass-ceramics (up to 900μm) resulted in adequate superficial tensions with 14% mechanical strength increase. Otherwise, the sodium content presented in sintered LZSA glass-ceramics after ion exchange (0.40–0.70wt.%) was distributed in an excessive exchange layer (up to 2000μm) which resulted in decrease of 42% on mechanical strength. For both glass-ceramics systems studied, an increase of Weibull modulus was verified.