Abstract: The object of the present application is ?-quartz glass-ceramics (having very interesting optical, thermal expansion and feasibility properties), the articles including said glass-ceramics; the precursor glasses of said glass-ceramics, as well as the methods for elaborating said glass-ceramics and said articles. Said glass-ceramics having a composition, free, except for inevitable trace amounts, of arsenic oxide, antimony oxide and rare earth oxide, which contains, expressed in percentages by weight of oxides: 64 to 70% of SiO2, 18 to 24% of Al2O3, 4 to 5% of Li2O, 0 to 0.6% of SnO2, >1.9 to 4% of TiO2, 1 to 2.5% of ZrO2, 0 to 1.5% of MgO, 0 to 3% of ZnO, >0.3 to 1 of CaO, 0 to 3% of BaO, 0 to 3% of SrO, with BaO+SrO?3%, 0 to 1.5% of Na2O, 0 to 2% of K2O, with 0.

Abstract: The present invention relates to a product, comprising a body which is delimited by a surface, of a lithium aluminosilicate-based glass-ceramic, as well as to its method of preparation. Characteristically, said glass-ceramic has, on at least one part of said surface, a surface layer the degree of crystallization of which is greater than that of said glass-ceramic within said body.

Abstract: The present invention relates to a product, comprising a body which is delimited by a surface, of a lithium aluminosilicate-based glass-ceramic, as well as to its method of preparation. Characteristically, said glass-ceramic has, on at least one part of said surface, a surface layer the degree of crystallization of which is greater than that of said glass-ceramic within said body.