TRANSPARENT, ESSENTIALLY COLORLESS AND NON-DIFFUSING BETA-QUARTZ GLASS-CERAMICS; ARTICLES IN SAID

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The present invention relates to transparent, essentially colorless and non-diffusing β-quartz glass-ceramics; to articles including said glass- ceramics; to precursor glasses of said glass-ceramics as well as to the methods for elaborating said glass-ceramics and said articles. Said glass-ceramics have a composition, free of arsenic oxide, antimony oxide and rare earth oxide except for inevitable trace amounts, which contains, expressed as percentages by weight of oxides : 62-72% of SiO2, 20-23% of Al2O3, 2.8- 5% of Li2O, 0.1-0.6% of SnO2, 1.9- 4% of TiO2, 1.6-3% of ZrO2, less than 0.4% of MgO, 2.5-6% of ZnO and/or BaO and/or SrO, less than 250 ppm of Fe2O3; and their crystallites present in the β-quartz solid solution have an average size of less than 35 nm, advantageously less than 30 nm. In addition to their interesting optical properties, the glass-ceramics of the invention present low thermal expansion and they are easily obtained, even at an industrial scale.