Zerodur Explained

Zerodur is a lithium-aluminosilicate glass-ceramic manufactured by Schott AG. Zerodur has a near zero coefficient of thermal expansion (CTE), and is used for high-precision applications in telescope optics, microlithography machines and inertial navigation systems.^{[1] [2] [3]}

Applications

The main applications for Zerodur include telescope optics in astronomy^[4] and space applications,^[5] lithography machines for microchips and displays,^[6] and inertial measurements systems for navigation.^{[7] [8]}

In astronomy, it is used for mirror substrates in large telescopes such as the Hobby-Eberly Telescope,^[9] the Keck I and Keck II telescopes,^[10] the Gran Telescopio Canarias,^[11] the Devasthal Optical Telescope,^[12] the European Southern Observatory's 8.2 m Very Large Telescope,^[13] and the 39 m Extremely Large Telescope.^[14]

In space, it has been used for the primary mirror of SOFIA’s telescope,^[15] for the imager in Meteosat Earth observation satellites,^[16] and for the optical bench in the LISA Pathfinder mission.^[17]

In microlithography, Zerodur is used in wafer steppers and scanner machines for precise and reproducible wafer positioning.^{[18] [19]} It is also used as a component in refractive optics for photolithography.^[20]

In inertial measurement units, Zerodur is used in ring laser gyroscopes.^[21]

Properties

Zerodur has both an amorphous (vitreous) component and a crystalline component. Its most important properties^[22] are:

• The material exhibits a particularly low thermal expansion, with a mean value of 0 ± 0.007×10⁻⁶ K⁻¹ within the temperature range of 0 to 50 °C.^{[23] [24]}
• High 3D homogeneity^[24] with few inclusions, bubbles and internal stria.
• Hardness similar to that of borosilicate glass.
• High affinity for coatings.
• Low helium permeability.
• Non-porous.
• Good chemical stability.
• Fracture toughness approximately 0.9 MPa·m^1/2.^{[25] [26]}

Physical properties

• Dispersion: (n_F − n_C) = 0.00967
• Density: 2.53 g/cm³ at 25 °C
• Young's modulus: 9.1 Pa
• Poisson ratio: 0.24
• Specific heat capacity at 25 °C: 0.196 cal/(g·K) = 0.82 J/(g·K)
• Coefficient of thermal expansion (20 °C to 300 °C) : 0.05 ± 0.10/K
• Thermal conductivity: at 20 °C: 1.46 W/(m·K)
• Maximum application temperature: 600 °C
• Impact resistance behavior is substantially similar to other glass^[27]

See also

• CorningWare
• Macor
• Ring laser gyroscope
• Sitall

References

1. Web site: Zerodur® . dead . https://web.archive.org/web/20110724234153/http://www.unitedlens.com/page175.html . July 24, 2011 . September 4, 2011.
2. Web site: Viens . Michael J . April 1990 . Fracture Toughness and Crack Growth of Zerodur . 28 August 2011 . NASA Technical Memorandum 4185 . NASA.
3. Web site: Schott AG Zerodur description . dead . https://web.archive.org/web/20140201215054/http://www.schott.com/advanced_optics/english/syn/advanced_optics/products/optical-materials/zerodur-zero-expansion-glass-ceramic/zerodur/index.html?so=uk&lang=english . February 1, 2014.
4. Döhring . Thorsten . May 2019 . Four decades of ZERODUR mirror substrates for astronomy . Proceedings, 4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes . 7281 . 10.1117/12.831423 . 10 May 2024.
5. Carré . Antoine . May 2023 . Comprehensive review of the effects of ionizing radiations on the ZERODUR® glass ceramic . Journal of Astronomical Telescopes, Instruments, and Systems . 9 . 2 . 10.1117/1.JATIS.9.2.024005 . 10 May 2024. free .
6. News: September 29, 2023 . SCHOTT Strengthens Glass Substrate Portfolio . Printed Electronics Now.
7. Web site: Sokach . Stephen . ZERODUR: The Highly Technical Glass-Ceramic . 10 May 2024 . Tech Briefs.
8. Web site: Zerodur . 10 May 2024 . Mindrum Precision.
9. Web site: Hobby-Eberly Telescope McDonald Observatory . 2024-07-12 . mcdonaldobservatory.org.
10. Web site: A Mirror’s Perfect Reflection . 10 May 2024 . W.M. Keck Observatory.
11. Web site: Description of the GTC . 10 May 2024 . Gran Telescopio CANARIAS.
12. Web site: 3.6 m DOT Telescope . July 7, 2024 . ARIES.
13. Web site: Very Large Telescope . 10 May 2024 . ESO.
14. Web site: Mirrors and Optical Design . 10 May 2024 . ESO.
15. Krabbe . Alfred . June 2000 . SOFIA telescope . Proceedings, Airborne Telescope Systems . 4014 . 10.1117/12.389103 . 10 May 2024. astro-ph/0004253 .
16. Web site: MTG (Meteosat Third Generation) - eoPortal . 2024-07-12 . www.eoportal.org . en.
17. Web site: LISA Technology Package Optical Bench Interferometer During Calibration . 10 May 2024 . ESA.
18. Web site: Hartmann . Peter . SCHOTT – Ultra low expansion glass ceramic ZERODUR . 10 May 2024 . Max-Planck-Institut für Astronomie . 49.
19. Jedamzik . Ralf . 2014 . Glass ceramic ZERODUR enabling nanometer precision . Proceedings, Optical Microlithography XXVII . 9052 . 10.1117/12.2046352 . 10 May 2024.
20. Mitra . Ina . September 2022 . ZERODUR: a glass-ceramic material enabling optical technologies . Optical Materials Express . 12 . 9 . 3563 . 10.1364/OME.460265 . 10 May 2024. free .
21. Pinckney . Linda R. . 2003 . Glass-Ceramics . Encyclopedia of Physical Science and Technology (Third Edition) . 807-816 . 10.1016/B0-12-227410-5/00293-3 . 10 May 2024.
22. Web site: ZERODUR® Extremely Low Expansion Glass Ceramic: SCHOTT Advanced Optics - SCHOTT AG. www.schott.com. 15 April 2018.
23. Web site: SCHOTT CTE Grades. https://web.archive.org/web/20131004223930/http://www.schott.com/advanced_optics/english/syn/advanced_optics/products/optical-materials/zerodur-zero-expansion-glass-ceramic/zerodur/index.html . dead . October 4, 2013.
24. http://optomechanicalservices.com/Papers.html
25. Web site: Viens . Michael J . April 1990 . Fracture Toughness and Crack Growth of Zerodur . 28 August 2011 . NASA Technical Memorandum 4185 . NASA.
26. Hartmann. P.. ZERODUR - Deterministic Approach for Strength Design. Optical Engineering. NASA. 18 December 2012. 51. 12. 124002. 10.1117/1.OE.51.12.124002. 2012OptEn..51l4002H. 120843972. PDF. 11 September 2013.
27. Senf. H. E Strassburger . H Rothenhausler . A study of Damage during Impact in Zerodur. J Phys IV France. 7. Colloque C3, Suppltment au Journal de Physique I11 d'aotit 1997. 1997. C3-1015-C3-1020. 10.1051/jp4:19973171. 31 August 2011.