A tool for local cooling by contact of a glass sheet at a temperature higher than 450 C., known as a contact tool, includes a contact face suitable for coming into contact with the glass sheet, the tool including an internal pipe for the circulation of a coolant, in particular air. The tool is used in a device for bending and/or cooling a glass sheet, in particular individual, the tool coming into contact with the glass sheet while it is held by a bending tool or by a cooling frame after bending. A compression zone is created that is capable of being drilled to form an edge having compressive stresses.

A tool for local cooling by contact of a glass sheet at a temperature higher than 450 C., known as a contact tool, includes a contact face suitable for coming into contact with the glass sheet, the tool including an internal pipe for the circulation of a coolant, in particular air. The tool is used in a device for bending and/or cooling a glass sheet, in particular individual, the tool coming into contact with the glass sheet while it is held by a bending tool or by a cooling frame after bending. A compression zone is created that is capable of being drilled to form an edge having compressive stresses.

Disclosed is an Er.sup.3+ doped Lu.sub.4Zr.sub.3O.sub.12 functional nanocrystal glass ceramic and a method of preparing the same. The glass ceramic comprises components in mole percentages of: 57% to 59% of SiO.sub.2, 12% to 16% of Al.sub.2O.sub.3, 14% to 18% of ZnO, 6% to 8% of Li.sub.2O, 3% to 5% of ZrO.sub.2, 2% to 3% of Lu.sub.2O.sub.3, 0.05% to 0.2 of Er.sub.2O.sub.3. Through composition design and heat treatment process control, the present invention achieves the controllable preparation of Er.sup.3+ rare-earth ion-doped Lu.sub.4Zr.sub.3O.sub.12 functional nanocrystals within the glass. This functional nanocrystalline glass has potential application value in low-temperature optical thermometry.