Synthetic Sapphire

Download Sapphire Datasheet (PDF, 247 KB)

SapphireSapphire is an anisotropic monoaxial crystal. It is one of the hardest and durable materials, chemically inert, with low friction coefficient, excellent optical and dielectrical characteristics, and thermal stability to 1600ºC. Its abrasion stability is by 8 times higher than that of steel. Due to these unique properties and wide optical transmission range (0.17 - 5.5 μm) sapphire is used as the material for production of UV, visible, and NIR optics for operation under critical conditions like high temperature, high pressure, chemically aggressive or abrasive environment.

Physical properties of sapphire

Chemical formula Al2 O3
Crystal class Hexagonal system, rhomboidal class 3 m
Lattice constants, A a=4.785, c=12.991
Density, g/cm3 3.98
Hardness 2000 with 2000 gidenter (Knoop)
9 (Mohs)
Optical transmission range, μm 0.17 - 5.5
Refractive index at 0.532 μm no =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 20ºC
280 at 500ºC
Elastic Coefficient C11=496, C12=164, C13=115
C33=498, C44=148

Thermal properties of sapphire

Melting point, K 2303
Specific heat, J/(kg x K) 105 at 91K
761 at 291K
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

Electrical properties of sapphire

Resistivity, Ohm x cm at 200-500ºC 1011 - 1016
Dielectric constant 10.0
Dielectric strength, V/cm 4 x 105
Loss tangent 1 x 10-4

Sapphire stability parameters

Main properties preservation to 1600ºC
Solubility
  -in water
  -in HNO3,H2SO4, HCl, HF
  -in alcalis
  -in melts of metals:
   Mg, Al, Cr, Co, Ni, Na, K, Bi, Zn, Cs
 
insoluble
insoluble to 300ºC
insoluble to 800ºC
 
insoluble to 800-1000ºC
g -radiation stability

No change in transmission above
2.5 μm after exposure to 107 Rads.
No visible coloration after exposure to
108 Rads/hr for 60 minutes at - 195ºC

Proton radiation stability
 
 
 
No change in transmission below
0.3 mm after exposure to 1012 proton/cm2
total dose

Sapphire refractive index vs wavelength

λ, μm
No
Ne
 
λ, μm
No
Ne
 
λ, μm
No
Ne
0.193
1.92879
1.91743
 
0.442
1.78038
1.77206
 
1.064
1.75449
1.74663
0.213
1.88903
1.87839
 
0.458
1.77843
1.77015
 
1.320
1.75009
1.74227
0.222
1.87540
1.86504
 
0.488
1.77530
1.76711
 
1.550
1.74618
1.73838
0.226
1.87017
1.85991
 
0.515
1.77304
1.76486
 
2.010
1.73748
1.72973
0.244
1.85059
1.84075
 
0.532
1.77170
1.76355
 
2.249
1.73232
1.72432
0.248
1.84696
1.83719
 
0.590
1.76804
1.75996
 
2.703
1.719
1.711
0.257
1.83932
1.82972
 
0.633
1.76590
1.75787
 
2.941
1.712
1.704
0.266
1.83304
1.82358
 
0.670
1.76433
1.75632
 
3.333
1.701
1.693
0.280
1.82437
1.81509
 
0.694
1.76341
1.75542
 
3.704
1.687
1.679
0.308
1.81096
1.80198
 
0.755
1.76141
1.75346
 
4.000
1.674
1.666
0.325
1.80467
1.79582
 
0.780
1.76068
1.75274
 
4.348
1.658
1.65
0.337
1.80082
1.79206
 
0.800
1.76013
1.7522
 
4.762
1.636
1.628
0.351
1.79693
1.78825
 
0.820
1.75961
1.75168
 
5.000
1.623
1.615
0.355
1.79598
1.78732
 
0.980
1.75607
1.74819
 
5.263
1.607
1.599

 

Transmission spectrum of 3 mm-thick sapphire window.

Fig. 1 Transmission spectrum of 3 mm-thick sapphire window.

For production of optics we use sapphire grown by Musatov method (Russian modification of Kyropulos method). We also offer shaped sapphire grown by Stepanov method (analogue of EFG process). 

Musatov sapphire

Musatov sapphire
Musatov sapphire is characterized by superior crystalline perfection, high optical homogeneity and minor internal defects. Advanced level of growth technology and special post-growth treatment allow getting UV-stable material. Great demand for the material nowadays and significant improvements both in technology and machining made it possible to get sapphire boules with the following overall dimensions – D300 mm and up to 250 mm length (along growth direction).

Sapphire is a slightly birefringent material and basically an application dictates the requirements to its orientation. For majority cases type of orientation is not so important and it is selected upon our choice basing on existing polishing technology. For laser application, sensors, illuminators as well as other viewing windows when the birefringence effect mush be minimized we use C-axis (<0001>) sapphire. For specific applications a precise orientation to meet customer' needs is also provided.

We had developed and have been using chemical-mechanical polishing process. Together with some improvements of the technology it allows us to produce high quality optical components (surface quality 20/10scr/dig, surface accuracy λ /10 @ 632 nm) which both are required for most exacting laser applications.

We offer the following products made of high quality Musatov sapphire:

1. Waveguides (lightguides) for medical application (for skin treatment and epilation)

Waveguides (lightguides) for medical application
Detailed information about these products is available in the chapter - Atypical Components.

During the last several years we have supplied more than thousand similar sapphire lightguides of various overall dimensions.

The lightguides with the following sizes: 10х20х25mm, 10x20х50mm и 20х20х50mm are available from stock.

2. Optics for laser and spectroscopy applications (windows, including wedged ones, prisms, lenses, mirrors)

Optics for laser and spectroscopy applicationsRange of the products for these applications is wide and herewith we only highlight our standard specifications as well as demonstrate some photos.

Windows for Nd:YAG laser

Windows for Nd:YAG laser





Specification:

Material Optical grade sapphire
Orientation C-axis
Tolerance for overall dimensions, mm +0/-0.12
Clear aperture, % >90
Tolerance for thickness, mm +/-0.1
Surface quality, scr/dig 20/10
Surface accuracy, fringes (N) <=6
Wedge , arc. min. < 5
Coating AR/AR @ 1064 nm, R<=0.6% per side

Sapphire windows with overall dimensions D10.5 x 1mm as well as D8 x 1mm are available from stock anytime.

Prisms

Prisms





Specification:

Material Optical grade sapphire
Tolerance for linear dimensions, mm +/-0.2
Clear aperture, % >85
Surface quality, scr/dig 40/20
Surface accuracy, fringes (N) <=4
Tolerance for angular dimensions, arc. min. +/-10
 

Lenses (plano-convex, plano-concave, meniscus)

Lenses






Specification:

Material Optical grade sapphire
Tolerance for diameter, mm +0/-0.2
Clear aperture, % >90
Effective focal length (EFL) tolerance, % +/-2
Tolerance for thickness, mm +/-0.2
Surface quality, scr/dig 40/20
Surface accuracy, fringes (N) < =4
Edge thickness variation (ETV), mm <=0.05
 

Protective windows for sensors

Protective windows for sensors






Specification:

Material Optical grade sapphire
Tolerance for overall dimensions, mm +0/-0.25
Clear aperture, % >90
Tolerance for thickness, mm +/-0.25
Surface quality, scr/dig 40/20
Wedge, arc. min. < 5
 

Sapphire windows with D25.4mm and D32mm of various thicknesses are available from stock anytime.

Special optics for spectroscopy (ATR elements)

ATR elements made of sapphire are unexpendable and used when an application dictates the exaggerated requirements to durability of the material, its chemical stability and non-toxicity. Upon customer' demand we drill the internal holes (both blind and through) into these parts, for example to place a thermocouple inside (see the photo). Minimal diameter is 0.5 mm.

Special optics for spectroscopy (ATR elements)








Specification:

Material Optical grade sapphire
Tolerance for linear dimensions, mm +/-0.1
Tolerance for angular dimensions, arc. min. +/- 6
Clear aperture, % >85
Surface quality:
-  plano surfaces, scr/dig
-  barrel

60/40
fine ground
 

3. Hyper-hemispherical, hemispherical, hypo-hemispherical, and balls

Such parts are widely used and depending on application can be classified as commodity goods. On the contrary Tydex specializes in production of custom-made elements in small and medium quantities (several tens per month). Recently it was discovered that similar sapphire parts can be successfully utilized as optics for THz range.

Hyper-hemispherical, hemispherical, hypo-hemispherical, and balls







Specification:

Material Optical grade sapphire
Available diameters, mm 2-25
Tolerance for overall dimensions, mm +/-0.25
Surface quality, scr/dig 80/50
Surface accuracy, mm 0.01 deviation from ideal sphere and plane
 

4. Precisely-oriented seeds to grow crystals

To grow some crystalline materials, for example Musatov sapphire boules, precisely-oriented seeds are required. Orientation tolerance of as grown crystal is caused by initial orientation of the seed. Our best achievable orientation tolerance is +/-10 arc. min.

Precisely-oriented seeds to grow crystals







Specification:

Material Optical grade sapphire
Orientation C -, A -, R-axis along a part' length (is specified by customer)
Orientation tolerance,
arc.  min.
+/-0.12
Wedge between the opposite surfaces, arc. min. < 3
Tolerance for overall dimensions, mm +/-0.25
Surface quality Fine ground
Groove ( for technological reasons) is specified by customer
 

For production of high quality optical components we use optical grades 1 - 4 (please see the classification of sapphire grades in the end of the chapter).  For less exacting applications and upon negotiation with a customer both technical grades (5 - 6) are used.

Stepanov shaped sapphire

Stepanov shaped sapphire
Machining of sapphire is limited by material hardness. Stepanov' technology provides control of both shape and orientation of sapphire crystal during its growth. It allows one to grow ribbons, rods, tubes, etc. Such parts require minimal post-growth machining or even do not require it at all. On one hand, this extends sapphire application fields considerably. On the other hand, this results in significant reduction of material and work consumption and, therefore, in the price reduction. Sapphire of optical quality (grades 3-4) as well as cost-effective construction grades are available.

Sapphire rods, tubes (including those sealed at one end), ribbons, as well as crystals with complicated cross-sections are available.

We may highlight such applications of single crystal shaped sapphire as protective envelopment for vapour lamps, high temperature electrical insulators, crucibles, optical light pipes, etc. It finds its place in nuclear, medical, research, industry and others fields.

Available sizes are:

  • Length: to 1 meter;
  • Cross section: 2-40 mm with tolerance +/-0.05 mm;
  • Weight: to 1 kg.

Additional parameters for tubes - minimal wall thickness is 0.5 mm, minimal inner diameter - 0.8 mm.

We offer the following products made of Stepanov sapphire:

Rods for subsequent production of lightguides, scalpels, cutters, and other components for various applications including medicine (ophthalmology, neurosurgery, cosmetology etc.) Tubes, including ones to be used as chemical utensils as well as seeds to grow nonlinear crystals
rods tubes
Tubes with variation of cross-section along their length including ones for utilization in MOCVD equipment used for epitaxial crystal growth Ribbons to be used as tracks to guide the units of multi-coordinate equipment
tubes with variation ribbons
Electrical insulators working at wide temperature and pressure ranges (parts of complex cross-section as well as drilled ones are available upon inquiry)
Various parts of complicated design
insulators Various parts of complicated design
Parts with external thread
Capillaries and multi-channel tubes for thermocouple covers. High thermal stability and durability of the sapphire make it key material for various critical applications
Parts with external thread Capillaries and multi-channel tubes for thermocouple covers
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 2mm 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 2mm from one another as well as bubbles clusters (which may include individual bubbles to 50μm) 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 1 - 4 grades as optical ones; 5 - 6 as technical (construction) 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.

Please pay attention that this article is only for your information. We do not supply sapphire in boules, ingots as well as semi-finished products. Our standard products are finished (polished, coated) parts.

For price quotation and delivery please fill in our request form.

 

 
Optics Stock
Optics is ready to be shipped!
Stock is updated weekly.

Terms&Conditions of Sale
Shipment/ Payment/ Warranty ...
Pulsed Terahertz Spectrometer
Tydex is proud to present Pulsed Terahertz Spectrometer - an integrated solution for broadband THz time-domain spectroscopy. It is ideal for scientific research applications!