Sapphire and Ruby Material Properties

Synthetic Sapphire and Ruby, also known as Corundum, have the same chemical composition, crystal structure and properties of the natural gemstones. Synthetic Sapphire is 99.99% pure Al2O3 and is clear and colorless. Ruby contains a trace of chromium to produce its red color making it easier to see and handle. Defining properties include durability, hardness (measuring 9 on the Mohs scale), non-porosity, corrosion resistance and chemical resistance, has excellent insulating properties and high thermal conductivity. A very pure material, It has good wear resistance and dimensional stability. Having superior optical transmission qualities this material is excellent for use with visible light, infrared and ultraviolet transmission and is regularly used in optical equipment.

Mechanical applications for precision balls include: bearings, valves, pumps, flow meters, metrology instrumentation, medical devices, probes.

Optical applications for precision balls include: lenses, fiber optics, bar code readers, medical devices.


Synthetic Sapphire Verneuil Crystals

PHYSICAL PROPERTIES
crystalline structure rhomboerdral hexagonal, single
composition Al2O3
purity 99.99%
main impurities Na2O, Si, Ca, Fe, Ga, Mg, Ti, Mn, Pb, Cu, Zn, Ni
cleavage conchoidal
density 3.99 – 9.98
dislocation density 109 – 108 / m2
THERMAL PROPERTIES
melting point 2320K
softening point 2070K
specific heat 7.5 · 102 j/kg · K at 300K
thermal conductivity 40 W / m · K ⊥ at 300K
thermal expansion 6.2 · 10-6/K ∥ C-axis
5.4 · 10-6/K ∥ C-axis
MECHANICAL PROPERTIES
hardness Mohs 9
Knoop 2200 face ∥ C-axis
Knoop 1800 face ⊥ C-axis
Young’s modulus 4.4 · 1011 Pa at 300K
modulus of rupture 4.0 · 108 Pa at 300K
compressive strength 2.1 · 109 Pa at 300K
tensile strength 1.9 · 108 Pa at 300K
Poisson’s constant 0.30
CHEMICAL PROPERTIES
acids and alkalis attack 0 at 570K
porosity 0
ELECTRICAL PROPERTIES
dielectric constant 10.6 electric field ∥ C-axis at 300K
8.6 electric field ⊥ C-axis at 300K
electrical resistivity 109 Ω · m at 770K
104 Ω · m at 1270K
109 Ω · m at 2270K
OPTICAL PROPERTIES
refractive index Nd at 0.5893 µm 1.760 face ∥ C-axis
1.769 face ⊥ C-axis
dispersive power (nf – nc) 0.011 λF = 0.4861 µm λC = 0.6563 µm
Transmission, disc thickness 1mm
visible light excellent
infrared 85% 0.75 – 5 µm
70% 5.5 µm
50% 6 µm
80% 0.4 – 0.3 µm
ultraviolet 60% 0.28 µm
50% 0.20 µm
*values are for guidance only