The present invention relates to novel glass and glass-ceramic materials, articles made from said novel glass-ceramics and to methods of preparing said novel glass-ceramics and articles. Said novel, transparent, translucent or opaque glass-ceramics, which contain, as main crystalline phase, a solid solution of .beta.-quartz or of .beta.-spodumene, essentially have the following composition, expressed as percentages by weight of oxides: 65 to 70% of SiO.sub.2; 18 to 23% of Al.sub.2O.sub.3; >4 to 5% of Li.sub.2O; 0 to <1% of MgO; 1 to 3% of ZnO; 0 to 2% of BaO; 1.8 to 4% of TiO.sub.2; 1 to 2.5% of ZrO.sub.2; 0.4 to 1% of K.sub.2O and/or Na.sub.2O; with, advantageously, an effective and non-excess amount of at least one fining agent. The glass-ceramic material is also characterized by a water content of .beta.-OH higher than 0.2 mm.sup.-1, preferably higher than 0.4 mm.sup.-1.
An alkali-free glass substrate containing, by mass percent, 50-70% of SiO.sub.2, 10-25% of Al.sub.2O.sub.3, 5-20% of B.sub.2O.sub.3, 0-10% of MgO, 0-15% of CaO, 0-10% of BaO, 0-10% of SrO and 0-5% of ZnO, also containing SnO.sub.2 and/or Sb.sub.2O.sub.3 and having a .beta.-OH value of at least 0.485/mm.
The invention relates to: a method of preparing glass-ceramics of .beta.-quartz and/or of .beta.-spodumene; a method of preparing articles made from said glass-ceramics; novel glass-ceramics of .beta.-quartz and/or of .beta.-spodumene; articles made from said novel glass-ceramics; and lithium aluminosilicate glasses, which are precursors of such novel glass-ceramics. The present invention relates to the use, as agent for fining the glass-ceramic glass precursor, of fluorine and at least one oxide of a multivalent element.
