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Originally Posted by tomsem
I’m waiting for transparent aluminum.
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"Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of
aluminium oxide"
Sapphire and diamond can both now be made synthetically at large sizes. The Star Trek technobabble was daft.
Sapphire was used from about 1700s as watch bearings and in the 1930s for autochanger record player stylus. Rubies and diamonds are also used in watches as bearings.
Auguste Verneuil invented the original process to make synthetic sapphire large enough for watch glasses in 1902.
Gorilla Glass also has aluminium in it and is a cheap alternative to sapphire for a phone screen outer layer.
https://en.wikipedia.org/wiki/Gorilla_Glass
One of the main competitors is in fact synthetic sapphire. The materials are neither rare nor expensive.
A diamond screen is possible. I don't know if diamond or sapphire is more crack resistant. Diamond is the hardest (most scratch resistant) natural material and sapphire the next hardest natural material. Diamond is unusual because it feels cold like copper being a good heat conductor, but if pure it's an insulator. Beryllium oxide is used as a heat conductive electrical insulator inside RF power transistors because it cheaper.
Diamond is kept artificially expensive by De Beers, AKA Element 12 Company.
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Synthetic sapphire—sometimes referred to as sapphire glass—is commonly used as a window material, because it is both highly transparent to wavelengths of light between 150 nm (UV) and 5500 nm (IR) (the visible spectrum extends about 380 nm to 750 nm[58]), and extraordinarily scratch-resistant.
The key benefits of sapphire windows are:
Very wide optical transmission band from UV to near-infrared, (0.15–5.5 µm)
Significantly stronger than other optical materials or standard glass windows
Highly resistant to scratching and abrasion (9 on the Mohs scale of mineral hardness scale, the 3rd hardest natural substance next to moissanite and diamonds)
Extremely high melting temperature (2030 °C)
Some sapphire-glass windows are made from pure sapphire boules that have been grown in a specific crystal orientation, typically along the optical axis, the c-axis, for minimum birefringence for the application.
The boules are sliced up into the desired window thickness and finally polished to the desired surface finish. Sapphire optical windows can be polished to a wide range of surface finishes due to its crystal structure and its hardness. The surface finishes of optical windows are normally called out by the scratch-dig specifications in accordance with the globally adopted MIL-O-13830 specification.
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Wikipedia