Transparent, essentially colorless, tin-fined las glass-ceramics with improved microstructure and thermal expansion properties

A lithium aluminosilicate glass-ceramic, containing a β-quartz solid solution as main crystalline phase, characterized in that:

• its composition, free, except for inevitable trace amounts, of arsenic oxide, antimony oxide and rare earth oxide, contains, expressed as weight percentages of oxides:
• 64 to 70% of SiO2,
• 18 to 24% of Al2O3,
• 4 to 5% of Li2 O,
• 0 to 0.6% of SnO2,
• >1.9 to 4% of TiO2,
• 1 to 2.5% of ZrO2,
• 0.1 to 1.5% of MgO,
• 0 to 3% of ZnO,
• >0.3 to 1 of CaO,
• 0 to 1.5% of BaO,
• 0 to 3% of SrO, with BaO +SrO ≤3%,
• 0 to 1.5% of Na2O,
• 0 to 2% of K2O, with 0.2≤(MgO+Na2O+K2O)/Li2O ≤1,
• 0 to 3% of P2O5,
• less than 200 ppm of Fe2O3;
• and
• the crystallites present in said β-quartz solid solution have an average size of less than 40 nm;
• wherein
• the lithium aluminosilicate glass-ceramic has:
• a total luminous transmittance, for a thickness of 5 mm, of more than 81%, a yellow index, for a thickness of 5 mm, of less than 14 and a haze percentage, for a thickness of 5 mm, of less than 2.5%;
• and
• a thermal expansion coefficient between 25° C. and any temperature between 300 and 700° C. (CTE25° C. −[300-700 ]) between + and −3.5, 107K −1.