Synthesis of Leucite Glass-ceramics for PFM Applications

Abstract

Aim: To synthesise novel fine-grain leucite glass-ceramics that are thermally compatible with non-precious metal substrates, by controlling the leucite crystal size and volume fraction within a glass matrix. Methods: Alumino silicate glass (1) was heat treated to produce a leucite glass-ceramic, then mixed with a thermally compatible alumino silicate glass (2) in different proportions and sintered. The glass/glass-ceramics specimens were characterised using X-ray diffraction, scanning electron microscopy, and differential dilatometry. Results: XRD indicated glass 1 was amorphous before heat treatment, and glass 2 was amorphous before and after sintering. After crystallisation heat treatment, glass 1 formed a bulk tetragonal leucite crystal phase. SEM images of the glassglass-ceramics mixtures exhibited very few visible micro-cracks. The micro-cracks in 100% glass-ceramic 1 only existed within the tetragonal leucite crystals which indicated that it was under compressive stress. Differential dilatometry of the glass-ceramics/glass mixtures showed a correlation (r2= 0.97) between coefficient of thermal expansion (CTE=100-400 °C) and the leucite weight fraction. Conclusion: A range of glass-ceramic veneering materials have been synthesised, and their coefficient of thermal expansion have been controlled. The produced glass/glass-ceramic materials appeared thermally compatible, and can be used for Y-TZP, precious metals, and non-precious metals.