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.

Applications

The main applications for Zerodur include telescope optics in astronomy and space applications, lithography machines for microchips and displays, and inertial measurements systems for navigation. In astronomy, it is used for mirror substrates in large telescopes such as the Hobby-Eberly Telescope, the Keck I and Keck II telescopes, the Gran Telescopio Canarias, the Devasthal Optical Telescope, the European Southern Observatory's 8.2 m Very Large Telescope, and the 39 m Extremely Large Telescope. It also has been used for the primary mirror of SOFIA's airborne telescope. In space, it has been used for the imager in Meteosat Earth observation satellites, and for the optical bench in the LISA Pathfinder mission. In microlithography, Zerodur is used in wafer steppers and scanner machines for precise and reproducible wafer positioning. It is also used as a component in refractive optics for photolithography. In inertial measurement units, Zerodur is used in ring laser gyroscopes.

Properties

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

Physical properties

History

Schott began developing glass-ceramics in the 1960s lead by Jürgen Petzoldt, in response to demand for low expansion glass ceramics for telescopes. In 1966, Hans Elsässer, the founding director of the Max Planck Institute for Astronomy (MPIA), asked the company if it could produce large castings of almost 4 meters using low-expansion glass-ceramic for telescope mirror substrates. In 1969, the MPIA ordered a 3.6 m mirror blank, along with ten smaller mirror substrates. The mirrors were delivered by late 1975, and went into operation in 1984 in a telescope at the Calar Alto Observatory in Spain. Further orders for mirror blanks followed.