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. ^{[2] [3] [4]}

Applications

The main applications for Zerodur include telescope optics in astronomy ^[5] and space applications, ^[6] lithography machines for microchips and displays, ^[7] and inertial measurements systems for navigation. ^{[8] [9]}

In astronomy, it is used for mirror substrates in large telescopes such as the Hobby-Eberly Telescope, ^[10] the Keck I and Keck II telescopes, ^[11] the Gran Telescopio Canarias, ^[12] the Devasthal Optical Telescope, ^[13] the European Southern Observatory's 8.2 m Very Large Telescope, ^[14] and the 39 m Extremely Large Telescope. ^[15]

In space, it has been used for the primary mirror of SOFIA’s telescope, ^[16] for the imager in Meteosat Earth observation satellites, ^[17] and for the optical bench in the LISA Pathfinder mission. ^[18]

In microlithography, Zerodur is used in wafer steppers and scanner machines for precise and reproducible wafer positioning. ^{[19] [20]} It is also used as a mirror substrate material in refractive optics for EUV lithography. ^[21]

In inertial measurement units, Zerodur is used in ring laser gyroscopes. ^[22]

Properties

Zerodur has both an amorphous (vitreous) component and a crystalline component. Its most important properties ^[23] 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. ^{[24] [25]}
• High 3D homogeneity ^[25] 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. ^{[26] [27]}

Physical properties

• Dispersion: (n_F − n_C) = 0.00967
• Density: 2.53 g/cm³ at 25 °C
• Young's modulus: 9.1×10¹⁰  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 ± 0.10×10⁻⁶/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 ^[28]

See also

• CorningWare
• Macor
• Ring laser gyroscope
• Sitall

References

External links