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 Keck I, Keck II, and SOFIA. With its very low coefficient of thermal expansion it can be used to produce mirrors which 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 x 10−7/K allows for highly accurate applications which require high-precision.
Zerodur has both an amorphous (vitreous) component and a crystalline component. Its most important properties are:
The Keck II
Telescope showing the segmented primary mirror made of Zerodur
- Measurement technology
- ^ http://www.unitedlens.com/page175.html
- ^ a b Viens, Michael J (April 1990). "Fracture Toughness and Crack Growth of Zerodur" (PDF). NASA Technical Memorandum 4185. NASA. Retrieved 28 August 2011.
- ^ a b Schott AG Zerodur description
- ^ Döhring, Thorsten; Peter Hartmann, Ralf Jedamzik, Armin Thomas, Frank-Thomas Lentes. "Properties of Zerodur Mirror Blanks for Extremely Large Telescopes" (PDF). Proc. of SPIE Vol. 6148 61480G-8. SPIE. Retrieved 26 August 2011.
- ^ Baer, JW; WP Lotz. "Figure testing of 300 mm Zerodur mirrors at cryogenic temperatures" (PDF). Retrieved 26 August 2011.
- ^ a b Schott AG Zerodur properties
- ^ SCHOTT CTE Grades
- ^ Hartmann, P. (18 December 2012). "ZERODUR - Deterministic Approach for Strength Design" (PDF). NASA. Retrieved 11 September 2013.
- ^ Senf, H; E Strassburger; H Rothenhausler (1997). "A study of Damage during Impact in Zerodur". J Phys Iv France (in English) 7 (Colloque C3, Suppltment au Journal de Physique I11 d'aotit 1997). Retrieved 31 August 2011.