High modulus glass-ceramic with fine grain spinel-type crystals

摘要

The present invention relates to a glass-ceramic article and a method of making the article that exhibits a Young's modulus between about 14 and 24 × 10 ⁶ psi and a crack stiffness greater than 1.0 MPa · m ^1/2 . Crystalline aggregates consist mainly of spinel-tile crystals of generally uniform size that are uniformly dispersed in the residual glass matrix phase of high silicic acid. The composition of the glass-ceramic product is expressed in terms of weight percent based on oxide, with 35% to 60% SiO ₂ , 20% to 35% Al ₂ O ₃ , and 0% to 25% MgO and at least 10% MgO + ZnO _2. It consists essentially of 0-25%, TiO ₂ 0-20%, ZrO ₂ 0-10%, LiO ₂ 0-2% and NiO 0-8%. However, if the Al ₂ O ₂ component participates in about 25% or less, the amount of TiO ₂ + ZrO ₂ + NiO should be at least 5%. The composition also comprises optional component 5 selected from the group consisting of BaO, CaO, PbO, SrO, P ₂ O ₅ , B ₂ O ₃ , Ga ₂ O ₃ , R ₂ O 0-5% and transition metal oxides 0-8% It may contain up to% said R ₂ O is selected from the group consisting of Na ₂ O, K ₂ O, Rb ₂ O and Cs ₂ O.