Study on Methods to Strenthen and Toughen Sapphire Crystal by Carbon Doped Grown by Temperature Gradient Technique (TGT)

Mechanical properties of carbon-doped sapphire crystals with different carbon concentrations were studied at room temperature. The present work showed that the fracture strength and fracture toughness of as grown crystals were significantly improved by carbon doping and the visible-infrared optical property did not adversely affect. When the concentration of doped carbon was 5×10 -3 , the fracture strength and fracture toughness were in- creased to 752 MPa and 2.81 MPa·m 1/2 in average, respectively, and the transmition of visible-infrared was about 80%. Appropriate carbon dopant in the crystals played the roles of clearance ions and created blocking effect to the sapphires cracking, which improved fracture strength and fracture toughness of sapphires at room temperature. However the mechanical properties and optical properties declined when carbon dopant was excessive, due to car-