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Opening of the ELT
secondary mirror ZERODUR® blank mould containing the glass at first annealing at the Schott AG
4-meter blank annealing facility in Mainz, Germany.
Zerodur (notation of the manufacturer: ZERODUR®), a registered trademark of Schott AG, is a lithium-aluminosilicate glass-ceramic produced by Schott AG since 1968. It has been used for a number of very large telescope mirrors including GTC, Keck I, Keck II, and SOFIA, as well as some smaller telescopes (such as the GREGOR Solar Telescope). With its very low coefficient of thermal expansion it can be used to produce mirrors that retain acceptable figures in extremely cold environments such as deep space. Although it has advantages for applications requiring a coefficient of thermal expansion less than that of borosilicate glass, it remains very expensive as compared to borosilicate. The tight tolerance on CTE, ±0.007×10-6 K-1, allows high-precision applications.
The Keck II
Telescope showing the segmented primary mirror made of Zerodur
- Measurement technology
Zerodur has both an amorphous (vitreous) component and a crystalline component. Its most important properties are:
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- ^ "Archived copy". Archived from the original on July 24, 2011. Retrieved 2011.CS1 maint: archived copy as title (link)
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- ^ a b Schott AG Zerodur description Archived February 1, 2014, at the Wayback Machine
- ^ Döhring, Thorsten; Peter Hartmann; Ralf Jedamzik; Armin Thomas; Frank-Thomas Lentes. "Properties of Zerodur Mirror Blanks for Extremely Large Telescopes" (PDF). Proc. SPIE. SPIE. Retrieved 2011.
- ^ Baer, JW; WP Lotz. "Figure testing of 300 mm Zerodur mirrors at cryogenic temperatures" (PDF). Retrieved 2011.
- ^ "ZERODUR® Extremely Low Expansion Glass Ceramic: SCHOTT Advanced Optics - SCHOTT AG". www.schott.com. Retrieved 2018.
- ^ SCHOTT CTE Grades Archived October 4, 2013, at the Wayback Machine
- ^ a b http://optomechanicalservices.com/Papers.html
- ^ Hartmann, P. (18 December 2012). "ZERODUR - Deterministic Approach for Strength Design" (PDF). NASA. Retrieved 2013.
- ^ Senf, H; E Strassburger; H Rothenhausler (1997). "A study of Damage during Impact in Zerodur" (PDF). J Phys Iv France. 7 (Colloque C3, Suppltment au Journal de Physique I11 d'aotit 1997). Retrieved 2011.