Contribution of gallium oxide content to the crystallization characteristics and chemical stability of sodium phlogopite glasses

The effect of gallium oxide content on the crystallization characteristics and chemical durability of a sodium phlogopite based glass-ceramic of the stoichiometric phase formula NaMg₃(Si₃Al_1−X,Ga_x]O₁₀)F₂ where X=0.0, 0.25, 0.5, 0.75 and 1.0 was investigated. The Ga₂O₃/Al₂O₃ replacement and heat treatment have an effect on the crystalline phases developed and their microstructure. Forsterite ss, enstatite, and sodium phlogopite phases were mostly detected in the crystallized glasses. There is a preferential tendency for forsterite to accommodate sodium phlogopite ions in its structure forming olivine solid solution of forsterite type. At low Ga₂O₃/Al₂O₃ replacement an increase in the crystallization temperature led to the decomposition of the sodium phlogopite phase to form forsterite ss phase, while at high Ga₂O₃ replacement increasing the heat-treatment temperature led to the development of forsterite ss at the expense of enstatite phase. The chemical stability of the crystallized materials was better in acidic than in alkaline media. The present data provides valuable information about the role played by the glass oxide constituent in determining the nature of the crystalline phases and solid solution formed in the materials especially in the field of preparation of glass-ceramic substrate used for magnetic information storage.