[spunkets]

The title is goofy. Aluminum is a metal. Aluminum oxide is already transparent and exists in crystaline and amorphous states. There is also no alloy here, the compound Al₂O₃ has simply been mixed with other compounds to effect structure. The goal is toughness. That's all.

[laishly]

Lead has been used in glass manufacture for eons. I never heard anyone call it "transparent lead."