Sapphire Crystals
Single crystal Sapphire possesses a unique combination of excellent optical, physical and chemical properties, the most
useful is that it is the hardest of the oxide crystals. Sapphire maintains its strength even at high temperatures. It has good
thermal properties, excellent electrical and dielectric properties, and is chemically resistant to common acids and alkali
at temperatures up to 1000℃ as well as to HF below 300℃.
Crystallographic properties
Syngony Hexagonal System
Crystal Form Poly or Single Crystal
Lattice Constant 7a=4.785, c=12.991
Cleavability <1011>, <1012>, imperfect
Physical properties
Density, g/cm3 at 20 ℃ 3.98
Hardness, Mohs 9
Dielectric Constant 102-108 Hz at 298 K Parallel to c-axis (//) 10.55
Perpendicular to c-axis (— ) 8.6
Melting point,℃ 2042
Thermal Conductivity, W/m·K at at 300 K 35.1
Parallel to c-axis (//) 33
Perpendicular to c-axis (— )  
Thermal Expansion, 1/K at 298 K 5.6 × 10-6
Parallel to c-axis (//) 5.0 × 10-6
Perpendicular to c-axis (— )  
Specific Heat Capacity, W×s/g/k 0.418
Bandgap, eV 9.9
Knoop Hardness, kg/mm2 1370
Youngs Modulus, Gpa 335
Shear Modulus, GPan 148
Bulk Modulus, Gpa at 273 K 240
Poissons Ratio 0.25
Elastic Coefficient C11=496, C12=164, C13=115, C33=498, C44=148
Apparent Elastic Limit 275 MPa (13000psi)

Ms. Lin

Mr. Wen