Aluminium Oxide
Al2O3
Chemical name
Aluminium Oxide
Mineral name
Sapphire, Corundum
Chemical formula
Al2O3
Melting point [°C]
2052
Crystal system
hexagonal, rhomboedric
Unit cell
a [Å]:4.758
b [Å]:4.758
c [Å]:12.991; a : c = 1 : 2.734
Twinning
twinfree
Mohs hardness
9
Density [g/cm3]
3.98
Color
colourless
Refractive Index
nd=1.8336 (at 265 nm); nd = 1.58638 (at 5.6 mm)
Piezoelectric crystals
 
thermal expansation coefficient [(10^(-5))/K]
0.54 || c-axis RT; 6.2 ^c-axis RT
 
Crystal growth method
Czochralski, HEM, Verneuil
Crystal growth orientation
(0001), (1102), (1012), (1010)
Maximum size
7 inch in diameter
Variations
doped crystals (Fe, Nb, Ti, W, Ta, V, Cr), other dopands on request
Dielectric constant
9.4 || c-axis RT; 11.5 ^c-axis RT
Dielectric loss tangent (10 GHz)
3.0*10^(-5) || c-axis RT; 8.6*10^(-5) ^c-axis RT
Specific resistivity [W/cm]
10^16
Transmission range
0.2 - 6.0 mm
Orientation
(0001), (1102), (1012), (1010)
Dispersion
0.011