solutions 1/2006 additional informations
ZERODUR® is an inorganic, non-porous glass ceramic. It owes approximately 70 to 78 percent of its weight to crystallites 30 to 50 nanometers in size and a remaining glassy phase. The crystallites contract when they are subjected to heat, whereas the glass itself expands. Thanks to the perfect mixture of ingredients, the thermal expansion coefficient is extremely low. In fact, between 0 and 50 degrees Celsius, it is nearly zero. The crystallites result after the molten glass has cooled to room temperature by continually tempering the glass over a period of several months, which means heating it slowly to nearly 1,000 degrees Celsius.
The resulting material is extremely homogeneous, chemically stable and can be processed and polished without difficulty. Among other things, it is used for optical elements in lithography, high-precision mechanical components and mirror substrates for astronomy. The chemical stability of ZERODUR® is so high that the aluminum coating of a mirror substrate can be removed and restored many times without affecting the optical characteristics of the mirror.