
Piezoelectric Quartz Crystal Production (1943) [video] - paulgerhardt
https://www.youtube.com/watch?v=b--FKHCFjOM
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philipkglass
It's notable how many of these steps are there just to deal with defects found
in the natural Brazilian quartz that the process starts with. In a 41 minute
video, it takes nearly until minute 18 before they're done identifying crystal
sections that are unusable just due to imperfections (mostly twinning) in the
original source material.

After the war, hydrothermally grown synthetic quartz crystals came to replace
Brazilian quartz. The move to synthetic crystals mitigated the strategic
dependency on quartz coming from specific distant geography. It also permitted
cheap, small fragments of any old quartz to be grown into high-quality
crystals. The synthetic crystals were free of twinning defects as-grown,
eliminating some inspection/removal steps. Their size could be made more
uniform than natural quartz, which permitted a higher degree of automation in
processing.

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pfdietz
I seem to remember seeing somewhere that the artificial quartz crystals could
also be doped to flatten their change in frequency with temperature.

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londons_explore
It's notable how large the crystals are.

Quartz crystals work pretty much independent of size. Since it's a hard-to-
obtain raw ingredient, and requires quite a lot of preprocessing before it's
useful, I'm surprised that the final crystal size used in the radios isn't
1mmx1mmx0.5mm or smaller, even with 1940's technology.

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monochromatic
I love these old-timey videos.

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joezydeco
Have you browsed the Prelinger Archives at archive.org?

[https://archive.org/details/prelinger](https://archive.org/details/prelinger)

