Effect of Li2O/CaO ratio on the structure and devitrification in Li2O-SiO2-CaO glass system

Abstract

The (33.33-X)Li2O:66.66SiO2-XCaO (X = 0, 1 and 2 mol %) glasses have been synthesized by melt quenching technique and then converted into glass-ceramics by a two-stage heat-treatment schedule. 29Si MAS-NMR study indicates that the CaO addition at the cost of Li2O increases Q3, Q2 units and decreases Q4 units in glasses. The glass transition temperature decreases with the addition of CaO. All the glass-ceramics exhibit Li2Si2O5 phase and the phase concentration decreases from 61.2 ± 0.2 to 48.93 ± 0.2 wt% with the addition of CaO. The glass–ceramic containing 1 mol % CaO has optimum conditions to exhibit the highest microhardness 5.95 ± 0.16 GPa.