Zerodur®, a registered trademark of Schott Glass Technologies, is a lithium aluminosilicate

Aluminosilicate

Aluminosilicate minerals are minerals composed of aluminium, silicon, and oxygen, plus countercations. They are a major component of kaolin and other clay minerals....

 glass-ceramic

Glass-ceramic

Glass-ceramics are polycrystalline material produced through controlled crystallization of base glass. Glass-ceramic materials share many properties with both glasses and ceramics...

 produced by Schott AG since 1968. It has been used for a number of very large telescope mirrors including Keck I and Keck II. With its very low coefficient of expansion it can be used to produce mirrors which retain acceptable figures

Figuring

Figuring is the process of final polishing of an optical surface to remove imperfections or modify the surface curvature to achieve the shape required for a given application.-Types of figuring:...

 in extremely cold environments such as deep space. Although it has advantages for applications requiring COE

Thermal expansion

Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are rare; this effect is...

 less than that of borosilicate glass

Borosilicate glass

Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. Borosilicate glasses are known for having very low coefficients of thermal expansion , making them resistant to thermal shock, more so than any other common glass...

 it remains very expensive as compared to borosilicate.

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

• Low thermal expansion (≈0.2 × 10⁻⁷/K at 0 °C–50 °C) which is an order of magnitude better than that of fused quartz
• High 3D homogeneity
  Homogeneity (physics)
  In general, homogeneity is defined as the quality or state of being homogeneous . For instance, a uniform electric field would be compatible with homogeneity...
  
   with few inclusions, bubbles and internal stria - (as contrasted to Cer-Vit
  Cer-Vit
  Cer-Vit aka CerVit or Cervit or Cer-Vit C-101 , is a glass-ceramic material made up of oxides of silicon, aluminium and lithium, with ultra low coefficient of thermal expansion, used for telesope mirrors and lenses. It was made by Owens-Illinois Corning in 1967, and discontinued in 1978...
  
  )
• Hardness similar to borosilicate glass
  Borosilicate glass
  Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. Borosilicate glasses are known for having very low coefficients of thermal expansion , making them resistant to thermal shock, more so than any other common glass...
  
   so that it can be ground and polished more easily than fused quartz
  Fused quartz
  Fused quartz and fused silica are types of glass containing primarily silica in amorphous form. They are manufactured using several different processes...
  
  
• High affinity for coatings
  Optical coating
  An optical coating is one or more thin layers of material deposited on an optical component such as a lens or mirror, which alters the way in which the optic reflects and transmits light. One type of optical coating is an antireflection coating, which reduces unwanted reflections from surfaces, and...
  
  
• Low helium permeability
• Non-porous - (as contrasted to sintered ceramics)
• Good chemical stability similar to that of fused quartz
  Fused quartz
  Fused quartz and fused silica are types of glass containing primarily silica in amorphous form. They are manufactured using several different processes...
  
  
• Fracture toughness approximately 0.9 MPa x m^1/2

Applications

1. Optics
2. Microlithography
3. Measurement technology

Properties

• Dispersion
  Dispersion (optics)
  In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency, or alternatively when the group velocity depends on the frequency.Media having such a property are termed dispersive media...
  
  : (nf − nc) = 0.00967
• Density
  Density
  The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
  
  : 2.53 g/cm³ at 25 °C
• Young's Modulus
  Young's modulus
  Young's modulus is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. In solid mechanics, the slope of the stress-strain...
  
  : 9.1 x 10¹⁰ Pa
  Pascal (unit)
  The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
  
  
• 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
  Thermal conductivity
  In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
  
  : at 20 °C: 1.46 W/(m·K)
• Maximum temperature: 600 °C
• Impact resistance behavior is substantially similar to other glass
  Glass
  Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...