Sapphire has excellent optical, thermal, mechanical, and electrical properties, and is a material used in a variety of fields. The recent increase in the size of sapphire crystals has led to an increase in the number of applications for applying sapphire, and the replacement and improvement from other materials is progressing.
| Formula |
α-Al2O3 (Corundum) |
|---|---|
| System |
Trigonal (R-3c) It is generally treated as a hexagonal. |
| Lattice constant |
a = 0.47588nm |
| Transmittance |
0.23～5.5μm（＞50% 5mmt Optical-Grade） |
|---|---|
| Refractive index |
no ＝ 1.7680 ne = 1.7598 （at 577nm） |
| Thermal conductivity |
115W/m・K(-120℃) |
|---|---|
| Specific heat |
0.75kJ/kg・℃ |
| Thermal expansion |
〈⊥ c-axis〉 |
| Bending strength |
470MPa (c-plane Length direction : //a-axis) |
|---|---|
| Hardness |
〈Mohs〉9 （※Diamond = 10 Quartz = 7） |
| Young’s modulus |
425GPa (Stress : ⊥ c-axis) |
| Poisson’s ratio |
0.30 (⊥c ／ ⊥c) |
| Relative permittivity |
9.41 (c-axis, 30GHz) |
|---|---|
| Loss tangent (tanδ) |
3×10-5 (c-axis, 30GHz) |
| Resistivity |
1011Ωcm (500℃) |
| Dielectric strength |
480kV/cm (60Hz) |
Chemical resistance（ Weight change of sapphire specimen, □25×0.5t, after 6 days of immersion）
| No change in weight（Δ = 0g） |
HCl (35%, 20℃) |
|---|---|
| Weight change micro |
HF (46%, 60℃) (Δ = 0.0038g/day) |
