Effect of Li ion additive on the structural evolution of nano-crystalline sodium-mica glass-ceramic derived via sol-gel route

The Li-added nanocrystalline sodium-mica glass-ceramic was synthesized through an aqueous sol-gel technique. The structural phase and microstructural characteristics of the samples were investigated by X-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The incorporation of Li ion into Na-mica composition (NaMg₃AlSi₃O₁₀F₂) up to 0.7 mol.% could be useful in development of the mica crystallization. Moreover, 8 h of heat treatment at 500 °C led to the formation of sufficient MgF₂ particles which acted as nucleation centers for mica crystallization at 750 °C. The crystallization activation energy of nucleated sample with 0.7 mol.% Li₂O was calculated as 304.4 kJ mol⁻¹. This value was 341.2 and 393.9 kJ mol⁻¹ for un-nucleated samples with 0.7 and 0 mol.% Li₂O, respectively; confirming the positive effects of nucleation process and Li ion addition on mica crystallization. The calculated Avrami parameter (n = 2.21) confirmed the predominance of bulk crystallization along with two-dimensional growth (flake like) of the mica crystals mechanisms of crystallization.