Properties and structure of (1 ? x)Li2O–xNa2O–Al2O3–4SiO2 glass systems

(1 ? x)Li₂O–xNa₂O–Al₂O₃–4SiO₂ glasses were studied for the progressive percentage substitution of Na₂O for Li₂O at the constant mole of Al₂O₃ and SiO₂. The crystallization temperature at the exothermic peak increased from 898 to 939 °C when the Na₂O content increases from 0 to 0.6 mol. The coefficient of thermal expansion and density of these as-quenched glasses increase from 6.54 × 10^?6 °C^?1 to 10.1 × 10^?6 °C^?1 and 2.378 g cm^?3 to 2.533 g cm^?3 when the Na₂O content increases from 0 to 0.4 mol, respectively. The electrical resistivity has a maximum value at Na₂O · (Li₂O + Na₂O)^?1 = 0.4. The activation energy of crystallization decreases from 444 to 284 kJ mol^?1 when the Na₂O content increased from 0 to 0.4 mol. Moreover, the activation energy increases from 284 kJ mol^?1 to 446 kJ mol^?1 when the Na₂O content increased from 0.4 to 0.6 mol. The FT-IR spectra show that the symmetric stretching mode of the SiO₄ tetrahedra (1035–1054 cm^?1) and AlO₄ octahedra (713–763 cm^?1) exhibiting that the network structure is built by SiO₄ tetrahedra and AlO₄.