Zerodur

Zerodur is a registered trademark of Schott Glass Technologies. It is a glass ceramic with an extremely low thermal expansion coefficient (~0.02 x 10^-6/K at 0-50°C). Zerodur belongs to the glass-ceramic composite class of materials and has both an amorphous (vitreous) component and a crystalline component.The most important properties of Zerodur are

• Nearly zero thermal expansion with outstanding 3D homogeneity
• High internal quality
• Good processing behaviour
• Can be polished to a very high accuracy
• Can be coated easily
• Low Helium permeability
• Non-porous
• Good chemical stability

Applications

1. Optics: Many optical applications such as telescopes, optical cavities etc require a substrate material with a near-zero coefficient of thermal expansion and/or excellent thermal shock resistance. Zerodur with its very small coefficient of thermal expansion at room temperature is such a material.
2. Microlithography: Zerodur is used as a movable mechanical part in wafer stepper and scanner machines to achieve precise and reproducible wafer positioning. Zerodur is an ideal substrate material for reflective optics in the forthcoming EUV lithography due to its almost zero thermal expansion, outstanding homogeneity and good processing behavior.
3. Measurement Technology: The extremely low thermal expansion and proven long-term dimensional stability of Zerodur make it an ideal reference standard for measurement instruments.

Zerodur Constants

• Dispersion: (nf - nc) = 0.00967
• Density: 2.53 g/cm³ at 25°C
• Young's Modulus: 9.1 x 109 dynes/mm²
• Poisson Ratio: 0.24 Specific Heat at 25°C: 0.196 cal/g°C
• Coefficient of thermal expansion (20° to 300°C) : 0.05 ± 0.10 x 10^-6/°C
• Maximum Temperature: 600°C