When it comes to tube and rod materials, transparent or not, sapphire tubes and sapphire rods are the go to material in so many applications. "Exceptional" applies to sapphire's performance under numerous conditions: mechanical, optical, thermal and chemical. In these cases, a sapphire tube or sapphire rod is without a peer. Why?

Sapphire is the hardest material next to diamond. It's almost impossible to make a diamond tube or rod. Sapphire is the 1st choice because:

  • Sapphire tubes are the best high-pressure containers and transport plumbing for many high-pressure systems. A sapphire tube can handle extreme pressures while allowing for safe observation and spectral analysis of fluids and gasses.
  • Sapphire tubes can be used in hostile environments to house sensitive sensors, protecting the sensors against pressure and mechanical abuse.
  • Sapphire rods are superior for rod bearing and standoff applications that involve high abrasion and wear while maintaining dimensional stability.

Sapphire Tube for Plasma Chamber




DID YOU KNOW: The term "jewel" in watch making comes from the recognition that sapphire and ruby jewels are far superior to any other available wear materials for precision watch and instrument making. This recognition drove the efforts to invent the first successful synthetic crystal growing process in the late 1800s, the Verneuil method. Over 100 years later sapphire is still the ultimate material for many applications that require high mechanical and wear properties.

Split Sapphire Tube

Sapphire transmits light from below 190nm to over 5 microns:

  • A sapphire tube is the ideal lamp material for UV and IR lamps because it can go far deeper into the UV and IR than any other lamp material. With its thermal robustness, a sapphire lamp can be exposed to extreme plasmas and temperatures, far greater than any other material, and continue to transmit high powered UV, visible and IR for years with no degradation.
  • A sapphire rod is the ideal material for pyrometry, transmitting a wide range of wavelengths. This makes sapphire rods the ideal product for hot zone temperature profiling with capabilities of measuring up to 2000C on one end of the rod while the other is at room temperature.
  • As with sapphire lamps, sapphire tubes can be used in extremely hostile environments to support UV, visible and IR sensor activities with no harm to delicate sensors.

Sapphire is highly robust at extreme temperatures and is readily available in tube and rod form:

  • A supported sapphire tube can be taken to 2000C with no change to its shape and minimal reduction to mechanical performance. Sapphire tubes are the perfect material for high temperature combustion tubes, gas processing and lamps.
  • Sapphire rods are ideal for rollers and standoffs in high temperature furnace systems. Sapphire rods remain straight and dimensionally "perfect" up to 1800C. Because of sapphire's extreme chemical resistance, many materials will not stick to sapphire in spite of high temperatures.
  • Sapphire tubes and rods maintain the highest temperature rating of all optical materials, in both oxidizing and inert atmospheres
  • Sapphire lamps can withstand considerably higher temperatures than the closest runner up material, fused silica, with zero degradation. Fused silica will degrade over time at temperatures almost half the maximum operating temperature of sapphire

Sapphire tubes and sapphire rods are incredibly chemical and plasma resistant:

  • Due to the extreme chemical resistance of sapphire tubes and rods at high temperatures, a sapphire tube is the ideal choice for plasma chambers and sapphire lamp applications.
  • Only hot caustic salts can etch sapphire rods and sapphire tubes. All other solvents, acids and caustics have no effect on sapphire, including molten metals. This property allows for safe, chemically pure chemical handling and processing.
  • Sapphire rods and tubes are so chemically and bio-inert, they are the perfect materials for medical, pharmaceutical, semiconductor and other applications where maintaining purity and health is critical.

Sapphire Rod

Rayotek has been fabricating micro to large sapphire tubes and rods for over 25 years. Although sapphire is often more costly than glass and other transparent materials, its exceptional properties can ultimately save money and reduce critical down time.

Synthetic sapphire is a single crystal form of corundum, aka, pure single crystal aluminum oxide, A12O3.  The combination of its unique properties make sapphire a preferred material for extreme mechanical, chemical & optical applications. Unlike glass, sapphire cannot be molded.  Sapphire can be grown into near net shapes such as tubes and rod, then ground and polished if necessary.
Industries Served Applications
Aerospace Windows, ball bearings, sensors
Medical Dental tool tips, endoscopy, camera lens cover
Oil & Gas Sight window without housing, gauges, diffusion plates
Military Windows, viewports, sensors, range finders
Research Containment tubes, cuvettes, lenses
Semiconductor Plasma tubes, lamps, lasers
Common Grades Description & Common Applications
  There are numerous sapphire growth methods & grades. Generally, the higher the grade the better the transmission in the UV and IR, and the less light scatter and lattice distortion.  The best grades, in particular, UV grade will not solarize.
Verneuil Original & simplest growth method, lowest cost, excellent for mechanical applications & situations where optical clarity is not critical. Good for lower quality watch crystals & observation ports
EFG (Stepanov) Edge defined growth method (to be exact, Edge-Defined Film-Fed Growth) for near net growth of tubes & large sheets. Better quality than Verneuil, but not  as pure & defect free as Kyropoulos or CZ. Excellent for most window applications including scanner windows & viewports and lower cost than Kyropoulos & HEM
Kyropoulos & CZ Excellent optical properties, ideal method for most optical applications except long exposure high UV & extreme power threshold requirements. Also preferred for high purity applications like semiconductor, LED fabrication & high purity chemistry
HEM The best quality sapphire, but difficult to acquire & considerably more costly compared to other grades. Quality compared to Kyropoulos usually not significant enough to justify cost for most applications. Best for extreme power & UV applications & for when zero fluorescence &/or high power threshold is required
Orientation Definition & Common Applications   
C-Axis Also known as the "optical axis". The only orientation that has almost zero birefringence for signals parallel to the C-axis. Used for optimal optical, mechanical, thermal & electrical performance.  In a rod or tube the typical C-axis orientation is along its length, in a window perpendicular to the face.
Random Parts are manufactured with no tracking of the crystal orientation.  Lower cost &  great for applications where orientation will not impact performance
Other  90 Degree (to C-axis), M-Plane, A-Plane, R-Plane
  Click for Orientation Definitions & Drawing
Properties Important Properties of Sapphire
  Thermal, physical/mechanical, optical, electrical & chemical
  Click for Sapphire Properties Data Sheet
Transmission & Other Curves Definition
  The overall transmission of sapphire is determined by purity. All quality sapphire materials transmit about the same in the visible wavelengths while higher purity creates better transmission in the UV and IR.  For all optical materials, including sapphire, the thinner the material the deeper it transmits into the UV and IR
  Click for Sapphire Optical & Thermal Properties Graph
  Click for Transparent Materials Transmissions Curves Graph
Surface Finish Description     
Polished Clear. Has little to no distortion & light scattering (depending on level of polishing). Ideal for optical applications, high purity semiconductor, chemical & vacuum processing
Fine Ground Frosted.  Ground surface roughness can be fine tuned for diffuser & low stiction applications. Tends to have micro-cracks that can trap water, gas & other impurities
As Grown Clear but not mechanically polished. Some optical distortion due to growth process but no micro cracks. Excellent for high vacuum systems such as plasma chambers & chemical processing where purity is critical but optical clarity is not
  Click for Surface Finish Photos
Surface Quality Definition & Rating
  The scratch-dig rating of surface quality is a qualitative rating based on comparing the actual surface to a scratch-dig standard. Pass or fail is somewhat subjective without clear dimensions to measure
80-50 Commercial quality such as car windshield and commercial windows
60-40 Good polish, good for commercial lenses and optics. Good for optics where light scatter is not a problem
40-20 Superior polish, good for higher performance optics and lower powered lasers. Reduced light scatter over 60-40
20-10 High Precision polish, extreme optics & good laser power threshold for medium powered lasers. Very little light scatter
 10-5 Highest surface quality, highest laser power threshold and lowest vulnerability to solarization. Exceptional optics with near-zero light scatter
  Click for Quality Scratch-Dig Definitions
Why Sapphire?  
  One of the hardest materials available
  Superior IR & UV transmission compared to other optical materials
  Highly scratch & abradant resistant
  Highly chemical resistant
  Maximum temperature rating of almost 2000C
  Excellent dielectric & loss tangent performance
Why Rayotek?  
  Onsite engineers & master optician
  25+ years of expertise in sapphire & exotic materials manufacturing
  ISO 9001:2008 Certified
  ITAR Registered
  State-of-the-art manufacturing equipment & measurement capabilities
  Cost saving overseas sourcing (for non-ITAR applications only)
  US Manufacturing at Rayotek's  30,000 SqFt facility +  partnerships in the U.S., China, Europe & Russia
Sapphire Services  
  Fire Polishing
  Laser Engraving
  Screen Printing


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