abstract |
The present invention relates to an article comprising at least one of a glass or glass-ceramic comprising Al 2 O 3 and at least one of REO or Y 2 O 3 , wherein at least 60 percent by weight of the glass or glass-ceramic collectively comprise the Al 2 O 3 and the at least one of REO or Y 2 O 3 , and wherein the glass or glass-ceramic contains not more than 20 percent by weight SiO 2 and not more than 20 percent by weight B 2 O 3 , based on the total weight of the glass or glass-ceramic. |