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Breakthrough using extremely rare earth https://en.wikipedia.org/wiki/Thulium https://en.wikipedia.org/wiki/Thulium which comes at a high price and only provide

Breakthrough using extremely rare earth https://en.wikipedia.org/wiki/Thulium https://en.wikipedia.org/wiki/Thulium which comes at a high price and only provides a low power laser? Wierd that the article says its low cost. Certainly not a holy grail.

_Microft 5y ago
Thulium is only required in small quantities. Here is a back-of-the-envelope calculation: molar mass of thulium: 169g/mol, density: 9.32g/cm3, i.e. 0.055 mol/cm^3 [0]. That's ~ 3.3*10^22 atoms per cubic centimeter. From the article: A thulium ion dopant concentration of 4.0 × 10^20 cm−3 was measured using Rutherford backscattering spectrometry. [1], i.e. a concentration of roughly 1/100 compared to pure material. Taking the first search result at face value, a cubic centimeter of 99.9% pure Thulium costs $85 [2]. Since the disks seem to have a diameter of 40μm, only a minuscule fraction of a cubic centimeter of material is needed for each. I would conclude that the material costs for these disks are not as large as initially assumed. [0] https://en.wikipedia.org/wiki/Thulium https://en.wikipedia.org/wiki/Thulium [1] https://onlinelibrary.wiley.com/doi/10.1002/lpor.202100348#page=8 https://onlinelibrary.wiley.com/doi/10.1002/lpor.202100348#p... (page 8, left column halfway down the page) [2] https://luciteria.com/metal-cubes/thulium-metal-cubes https://luciteria.com/metal-cubes/thulium-metal-cubes
jjk166 5y ago
The term rare earth is a bit misleading. It's not rare as in uncommon, it's rare as in dilute. Rare earths are elements that don't form concentrated ores, and instead are spread diffusely in common rocks. Most soils contain between 0.4 and 0.8 ppm Thulium. Luckily Earth has a lot of rock, so in absolute terms there are still lots of rare earth material. The problem is that rare earths are mined by processing prodigious amounts of earth, typically the waste from some other mining activity. Like most large scale mining operations, it is labor intensive and environmentally destructive. Naturally this leads to such operations being located where labor is cheap and environmental regulations are lax. When people express concern about access to Rare Earths, they really mean access to materials from countries (often one specific country) with cheap labor and poor regulation. Thulium's expense is due to limited production, as there are few industrial uses for it and those applications that do utilize it tend to need only microscopic amounts, but with high purity.

_Microft 5y ago

Thulium is only required in small quantities. Here is a back-of-the-envelope calculation: molar mass of thulium: 169g/mol, density: 9.32g/cm3, i.e. 0.055 mol/cm^3 [0]. That's ~ 3.3*10^22 atoms per cubic centimeter. From the article: A thulium ion dopant concentration of 4.0 × 10^20 cm−3 was measured using Rutherford backscattering spectrometry. [1], i.e. a concentration of roughly 1/100 compared to pure material. Taking the first search result at face value, a cubic centimeter of 99.9% pure Thulium costs $85 [2]. Since the disks seem to have a diameter of 40μm, only a minuscule fraction of a cubic centimeter of material is needed for each. I would conclude that the material costs for these disks are not as large as initially assumed. [0] https://en.wikipedia.org/wiki/Thulium https://en.wikipedia.org/wiki/Thulium [1] https://onlinelibrary.wiley.com/doi/10.1002/lpor.202100348#page=8 https://onlinelibrary.wiley.com/doi/10.1002/lpor.202100348#p... (page 8, left column halfway down the page) [2] https://luciteria.com/metal-cubes/thulium-metal-cubes https://luciteria.com/metal-cubes/thulium-metal-cubes

jjk166 5y ago

The term rare earth is a bit misleading. It's not rare as in uncommon, it's rare as in dilute. Rare earths are elements that don't form concentrated ores, and instead are spread diffusely in common rocks. Most soils contain between 0.4 and 0.8 ppm Thulium. Luckily Earth has a lot of rock, so in absolute terms there are still lots of rare earth material. The problem is that rare earths are mined by processing prodigious amounts of earth, typically the waste from some other mining activity. Like most large scale mining operations, it is labor intensive and environmentally destructive. Naturally this leads to such operations being located where labor is cheap and environmental regulations are lax. When people express concern about access to Rare Earths, they really mean access to materials from countries (often one specific country) with cheap labor and poor regulation. Thulium's expense is due to limited production, as there are few industrial uses for it and those applications that do utilize it tend to need only microscopic amounts, but with high purity.