Sapphire (Al2O3)
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single-crystal single-crystal Sapphire
single-crystal Sapphire
single-crystal Sapphire
Synthetic Sapphire is a single crystal form of corundum, Al2O3, also known as alpha-alumina, alumina, and single crystal Al2O3. Sapphire is aluminium oxide in the purest form with no porosity or grain boundaries, making it theoretically dense. The combination of favourable chemical, electrical, mechanical, optical, surface, thermal, and durability properties make sapphire a preferred material for high performance system and component designs. For various semiconductor applications, sapphire is the best choice in comparison with other synthetic single-crystals.
   Sapphire substrates / wafers: EPI-polished, optically polished, lapped or as-cut sapphire disks, windows, substrates, blanks as well as epitaxial structures “silicon-on-sapphire” (SOS) are described at the next page, Sapphire for electronic applications.
Main properties of sapphire:
Chemical formula Al2O3
Crystal class Hexagonal system, rhomboidal class 3m
Lattice constants, A a=4.785, c=12.991
Density, g/cm3 3.98
Melting point, °K 2303
Hardness Knoop(daN/mm2): 1800 parallel to C-axis, 2200 perpendicular to C-axis, Mohs: 9
Optical transmission range, µm 0.17 - 5.5
Refractive index at 0.532 µm n0=1.7717, ne=1.76355
Water absorption nil
Young Modulus, Gpa 345
Shear Modulus, Gpa 145
Bulk Modulus, Gpa 240
Bending Modulus (Modulus of Rupture), Mpa 420 at 20°C, 280 at 500°C
Elastic Coefficient C11=496, C12=164, C13=115, C33=498, C44=148
Poisson ratio 0.25-0.30
Friction Coefficient 0.15 on steel, 0.10 on sapphire
Tensile strength, MPa

400 at 25°, 275 at 500°, 345 at 1000°

Flexural strength, daN/mm2

35 to 39

Compressive strength, GPa


Young’s modulus E, daN/mm2

3.6 x 104 to 4.4 x 104

Specific heat, J/(kg x K)
105 at 91°K, 761 at 291°K
Thermal coefficient of linear expansion, K-1,at 323K 6.66 x 10-6 parallel to optical axis, 5 x 10-6 perpendicular to optical axis
Thermal conductivity, W/(m x K) at 300K
23.1 parallel to optical axis, 25.2 perpendicular to optical axis
Resistivity, Ohm x cm 1016 (25°), 1011 (500°), 106 (1000°)
Dielectric constant 11.5 (103 - 109 Hz, 25°) parallel to C-axis, 9.3 (103 - 109 Hz, 25°) perpendicular to C-axis
Dielectric strength, V/cm 4 x 105
Loss tangent 1 x 10-4
  -in water
  -in HNO3,H2SO4, HCl, HF
  -in alcalis
  -in melts of metals  Mg, Al, Cr, Co, Ni, Na, K, Bi, Zn, Cs
insoluble to 300°C
insoluble to 800°C 
insoluble to 800-1000°C
g -radiation stability No change in transmission above 2.5 mm after exposure to 107 Rads. No visible coloration after exposure to 108 Rads/hr for 60 minutes at - 195°C
Proton radiation stability  No change in transmission below 0.3 µm after exposure to 1012 proton/cm2 total dose
Chemical resistance
Sapphire is highly inert and resistant to attack in most process environments including hydrofluoric acid and the fluorine plasma applications commonly found in semiconductor wafer processing (NF3, CF4)

We can deliver the Sapphire material produced by each of the three different methods of sapphire growth:
Kyropolis method The crystallization process starts with the bait because of the minimal temperature of the melt. The shape and size of the crystal depends on the thermic field. In this method the melt level is being lowered due to the difference in the crystal and melt concentration.
The growth speed is 0.15 kg/hour, the crystal diameter is 100 to 240 mm.
The process is highly automated.
Kyropolis method is used to produce a large boule of sapphire, most typically of a cylindrical form. As-grown boule can be from 70 up to 200 mm in diameter and up to 250 mm in height. Sapphire grown by this method normally has a very high optical quality, and can be cut into wafers of any crystallographic orientation. This method is applied for manufacturing substrates for blue LEDs and SOS wafers.
Bagdasarov method Crystals are grown from the melt in a horizontal boat-shaped container. This method makes it possible to get big and perfect single crystals.
Growth speed is 8-10 mm/hour, blank size is 320 x 115 x 30 mm.
Bagdasarov method produces sapphire in a slab form, making it possible to get very thick windows and components. Typical crystals grown by this method have a form of thick window (180mm x 150 mm x 25 mm). This material possesses high optical quality, and is ideal for manufacturing sapphire windows of large diameters. This material can be also used for producing wafers for blue LEDs.
Stepanov method (EFG) Growth speed is 1 to 4 cm/hour in Inert medium (argon).
The method makes it possible to grow crystals of complicated shape.
Blanks (ribbons) 80 mm thick and 300 mm long can be produced.
Stepanov (or EFG) method - a shaped growth technique used for growing sapphire in near-net finished shape, including tubes, rods, sheets, and fibers. This technique can also provide unique shapes and sealed assemblies. By Stepanov method, ribbon crystals up to 500 mm long and 80 mm wide are grown. Crystals grown by this method can have different crystallographic orientations (A, R, random) and are mainly used for industrial & mechanical applications, where good optical qualities are not important.

Typical Sapphire applications:

Sapphire substrates:
· Blue LED's (BLED's) - sapphire is the substrate for the growth of III-V and II-VI compounds such as GaN for LED's,
· for IR Detectors, for the growth of mercury cadmium tellurium (HgCdTe), GaAs wafer carriers, microwave integrated circuits
· Sapphire is used for its durability and erosion/corrosion resistance, often in combination with the ability to withstand high heat while having a very broad transmission range. Applications include:
· Windows - FLIR (Forward Looking Infra Red) windows for sensors and other optics. Optical clarity over a broad spectral range combines with durability in this application.
· Windows - for erosion resistance in salt and blowing sand environments, sapphire is used in conventional windows and dome shapes in replacement of softer, more fragile IR transmitting materials.
· Countermeasures lamps - sapphire flash lamps are used in IRCM's (Infra red countermeasures). The high temperature performance of sapphire is combined with broad spectral range in this application.
Analytical applications:
· Sapphire is used in analytical applications where combinations of high temperature, pressure, and hydrofluoric acid species are encountered. These applications need the survivability of sapphire, while often needing other   properties such as favourable UV (ultraviolet) or IR (infrared) transmission.
· NMR (Nuclear Magnetic Resonance) tubes; Sapphire is used for very high-pressure applications in replacement of glass or quartz tubes.
· Sample preparation - sapphire is used in digestion cells as sheaths and liners. When hydrofluoric acid is used, sapphire replaces quartz components
· Analytical chemistry - for mass spectroscopy, ICAP, and other systems, sapphire replaces quartware to improve durability and reduce contamination while offering good UV transmission.
Medical applications:
· Sapphire is used in surgical systems for laser transmission and in contact with bodily fluids.
· Surgical tips - sapphire is used in contact tips for various surgical laser applications
· Endoscope lenses - sapphire is often used in endoscope lenses due to its durability in contact with tissues and in sterilisation environments such as autoclaving
· Sapphire knives - with a sapphire knife, thinner sections are possible. The near perfect cutting edge of this knife / blade gives distortion-free sections down to 10 microns thick.
Optical applications:
· Sapphire is used for short and long wavelength applications (UV and IR) beyond the range where conventional optics performs adequately. High temperatures and hostile environments also necessitate the use of sapphire optics.
· Illumination windows - for very high brightness illumination, sapphire windows survive the very high heat while providing the broadest spectral transmission.
· Sapphire lightguides - sapphire rods; used in high temperature thermometry beyond the range of quartz optics.
· Optical components: lenses, prisms and other laser and infrared optics are fabricated from high optical quality sapphire.
Watch industry: Sapphire is widely used for watch glasses. The world demand in watch industry centres on scratchproof sapphire watch crystals. However, besides traditional flat shapes, crystals with spherical and cylindrical   curves are also in great demand.

Typical specifications:

Available orientations:

C-axis [0001], R-axis [1-102], A-axis [11-20], M-axis [10-10], Random

Sapphire windows / blanks

Diameter / Width:

25.0 - 250.0 mm


Standard ± 2°, Special to ± 0.1°


Minimum 0.15, maximum 120.0 mm

Surface finish:

As cut, fine ground, lapped, polished s/d 80/50, 60/40, 40/20, 20/10, 10/5, according to the MIL-0-13830A

Ends / Edge quality:

Fine ground, 80/50

"As-grown" sapphire tubes:
Dimensions Up to 50 mm inner diameter, 0,5 - 4,0 mm wall thickness, 300-600 mm tubes length
Orientation C-axis in the length of the tube
Polished sapphire tubes: Up to 50 mm inside diameter, 0,5 - 3,0 mm wall thickness, 80-350 mm tubes length
Ingots: Diameter/Width 5-220 mm, Thickness/Length 25 – 125 mm
Surface quality As-cut, Ends/Edge Quality Diamond cut

Sapphire quality grades:
  • Grade 1: free of insertions, block boundaries, twins, microbubbles and scattering centers;
  • Grade 2: free of insertions, block boundaries, twins; individual scattering centers (microbubbles < 10 µm located not closer than 10 mm) are allowed;
  • Grade 3: free of insertions, block boundaries, twins; individual bubbles < 20 µm located not closer than 10 mm to each other are allowed;
  • Grade 4: free of insertions, block boundaries, twins; bubbles < 20 µm located not closer than 2 mm from one another as well as bubbles clusters (which may include individual bubbles to 50 µm) of size < 200 µm scattered not closer than 10 mm to each other within the effective volume 20x20x20 mm are allowed;
  • Grade 5: free of insertions, block boundaries, twins; bubbles < 20 µm located not closer than 2 mm from one another as well as bubbles clusters (which may include individual bubbles to 50 µm) of size < 500 µm scattered not closer than 5 mm to each other within the effective volume 20x20x20 mm are allowed;
  • Grade 6: free of insertions, block boundaries, twins; defective areas with bubbles clusters of size > 500 µm are allowed.
We consider grades 1-4 as optical ones; 5-6 as technical ones. For all optical grades, blue and green coloration is not allowed. For all technical grades, coloration is not controlled. Insertions, block boundaries and twins inside the material are controlled visually between crossed polarizers.

I N Q U I R Y    F O R M :

Quantity of elements:

polished sites:

 a-b b-c a-c
or d  
For example:
10.0 +/- 0.1
a = mm;
c = mm
b = mm or
dia. = mm;
This field is for additional information such as application,
comments, add. requirements etc.

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