| 摘要 |
A transparent glass-ceramic article of a unitary structure composed of an interior portion and an exterior portion, wherein the interior portion containing a crystalline phase comprises (a) 55 to 75% by weight of SiO2, (b) 15 to 30% by weight Al2O3, (c) 2 to 6% by weight of Li2O (d) 1 to 5% by weight of Na2O, and (e) 2 to 9% by weight of TiO2+ZrO2P2O5, the total amount of the components (a) to (e) being 95 to 100 by weight, and wherein the exterior portion has the same glass composition as the interior portion but at least a part of Na+ in the exterior portion is exchanged with K+.
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