Crystallization processes of Li2O–Ga2O3–SiO2–NiO system glasses

Abstract Crystallization processes of Li 2 O–Ga 2 O 3 –SiO 2 –NiO system glasses have been studied by X-ray diffraction, differential calorimetry and optical absorption. Transparent glass-ceramic containing LiGa 5 O 8 :Ni 2+ as the sole crystalline phase has been obtained from glass with the composition of 13Li 2 O–23Ga 2 O 3 –64SiO 2 –0.1NiO (in mol%) by the heat treatment in the temperature range from 923 to 953 K. It was revealed that the specific surface area of samples enhances crystallization of LiGaSi 2 O 6 but obstructed that of LiGa 5 O 8 . LiGa 5 O 8 grew to nano-sized crystallites dispersed in the glass matrices and did not affect the transparency seriously. In contrast, LiGaSi 2 O 6 grew to crystallites with diameters more than 100 nm on the surface and made the glasses opaque. Optical absorption measurements revealed that doped Ni 2+ occupied five-folded trigonal bipyramidal sites in the as-quenched glass matrices but six-folded octahedral sites of precipitated LiGa 5 O 8 in the glass-ceramics. It was confirmed that transparent glass-ceramic containing Ni 2+ :LiGa 5 O 8 was effectively obtained by the heat treatment at a temperature of 953 K for 10 h.