Glass-ceramics

Glass-ceramics are polycrystalline materials produced through controlled crystallization of base glass, producing a fine uniform dispersion of crystals throughout the bulk material. Crystallization is accomplished by subjecting suitable glasses to a carefully regulated heat treatment schedule, resulting in the nucleation and growth of crystal phases. In many cases, the crystallization process can proceed to near completion, but in a small proportion of processes, the residual glass phase often remains.

surface reactive glass-ceramic biomaterial

thumb|300px|Opening of the European Extremely Large Telescope|ELT secondary mirror Zerodur blank mold containing the glass at first annealing at the [[Schott AG 4-meter blank annealing facility in Mainz, Germany.]] 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.

American chemist (1915-2014)

Sitall (also known as Sitall CO-115M or Astrositall) is a crystalline glass-ceramic with ultra-low coefficient of thermal expansion (CTE). It was originally manufactured in the former Soviet Union and was used in the making of primary mirrors for the Russian Maksutov telescopes. It has a CTE of only 0 ± 1.5 °C−1 in the temperature range −60 to 60 °C, placing it in a small group of transparent materials with low CTE such as Vycor, Zerodur, CerVit and fused quartz.