Glass-ceramics suitable for ring laser gyros

Claim 1

A highly crystalline, virtually haze-free, glass-ceramic body exhibiting extremely high optical transparency, a coefficient of thermal expansion over the temperature range of -50° to +100° C. between -1 to +1×10 -7 /°C., long term thermal stability, and excellent resistance to permanent deformation during thermal cycling, and containing β-quartz solid solution crystals having diameters of less than about 500 Å as essentially the sole crystal phase, consisting essentially, expressed in terms of weight percent on the oxide basis, of: ______________________________________ SiO.sub.2 64-67 ZnO 0.7-4.2 Al.sub.2 O.sub.3 21-24 TiO.sub.2 2.0-3.25 Li.sub.2 O 2.6-3.7 ZrO.sub.2 1.25-2.5 MgO 0.8-1.5 TiO.sub.2 + ZrO.sub.2 4-5.25 ______________________________________

Claim 4

A method for making a highly crystalline, virtually haze-free, glass-ceramic body exhibiting extremely high optical transparency, a coefficient of thermal expansion over the temperature range of -50° to +100° C. between -1 to +1×10 -7 /°C., long term thermal stability, and excellent resistance to permanent deformation during thermal cycling, and containing β-quartz solid solution crystals having diameters of less than about 500 Å as essentially the sole crystal phase, comprising the steps of: (a) melting a batch for a glass consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 64-67 ZnO 0.7-4.2 Al.sub.2 O.sub.3 21-24 TiO.sub.2 2.0-3.25 Li.sub.2 O 2.6-3.7 ZrO.sub.2 1.25-2.5 MgO 0.8-1.5 TiO.sub.2 + ZrO.sub.2 4-5.25 ______________________________________ (b) cooling said melt to a temperature at least below the transformation range thereof and simultaneously forming a glass article therefrom; (c) heating said glass article to a temperature between about 700°-750° C. and maintaining a temperature within that range for a period of time sufficient to develop nuclei therein; (d) heating said article with nuclei therein at a rate not exceeding about 75° C./hour to a temperature between about 800°-900° C. and maintaining a temperature within that range for a period of time sufficient to grow submicroscopic crystals of β-quartz solid solution on said nuclei to form a glass-ceramic article; and then (e) cooling said glass-ceramic article to room temperature.

Claim 5

A method for making a highly crystalline, virtually haze-free, glass-ceramic body exhibiting extremely high optical transparency, a coefficient of thermal expansion over the temperature range of -50° to +100° C. between -1 to +1×10 -7 /°C., long term thermal stability, and excellent resistance to permanent deformation during thermal cycling, and containing β-quartz solid solution crystals having diameters of less than about 500 Å as essentially the sole crystal phase, comprising the steps of: (a) melting a batch for a glass consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 64-67 ZnO 0.7-4.2 Al.sub.2 O.sub.3 21-24 TiO.sub.2 2.0-3.25 Li.sub.2 O 2.6-3.7 ZrO.sub.2 1.25-2.5 MgO 0.8-1.5 TiO.sub.2 + ZrO.sub.2 4-5.25 ______________________________________ (b) cooling said melt to a temperature at least below the transformation range thereof and simultaneously forming a glass article therefrom; (c) heating said glass article to a temperature between about 700°-750° C. and maintaining a temperature within that range for a period of time sufficient to develop nuclei therein; (d) heating said article with nuclei therein at a rate not exceeding about 75° C./hour to a temperature between about 800°-900° C. and maintaining a temperature within that range for a period of time sufficient to grow submicroscopic crystals of β-quartz solid solution on said nuclei to form a glass-ceramic article; and then (e) cooling said glass-ceramic article to room temperature.