sapphire sheet is a form of synthetic sapphire glass that’s used to make the display screens on smartphones. It’s made by mixing aluminium oxide, a “sapphire seed” and uncrystallised sapphire in a furnace and then cutting the material into paper-thin sheets.
A wide range of crystalline grades are available, with the most optically clear grade (also known as zero-degree) having little light scatter or lattice distortion. This is the best choice for high end applications where optical transparency and strength are crucial, such as screen lenses in high-end watch faces, hematology inspection filters, and the shatter-resistant windows in military body armor suits.
Edge Fed Growth technology gives sapphire crystals the ability to be produced into a variety of shapes. This enables the production of tubes up to 3″ diameter and windows up to 1 ft x 3 ft, with a range of cross-sectional growth options including square, rectangular, round, and even complex bonded shapes.
Orientation: The crystalline orientation in sapphire is important for the physical properties of the sheet. The optimum crystallographic orientation depends on many factors, including birefringence, thermal expansion, and lattice constants.
One of the most common is C-plane, and this is what is referred to as “zero-degree” sapphire. However, sapphire can be oriented in other ways to optimize its use for certain application requirements.
In addition, the sapphire sheets may have different secondary orientations with respect to each other, as discussed above. A first sheet 154 may have a secondary orientation that provides chipping resistance, whereas a second sheet 156 may have a secondary orientation that is advantageous for strength.