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Synthetic Sapphires: by popular demand

Last week on the Goodfellow blog, we took a spotlight to Alumina. In this post, we mentioned that this material goes into the making of synthetic Sapphires and Rubies. This week, as requested by some of our readers, we’re going to take a closer look. So, take this edition as a “you asked we answered”… As Ruby exhibits identical properties to those of Sapphire, we’re going to focus on Sapphire today.

Sapphire, the single crystal form of corundum or else (alpha) Alumina, was originally synthesised over a century ago. Although not a new thing, the more exciting advances are taking place in the present. Synthetic Sapphire material is a popular choice for design engineers when dealing with extreme conditions, including high temperature, high pressure and harsh chemicals.

Performance Profile & Properties

A lesser-known fact about Sapphire is that it’s second only to diamond in hardness and scratch resistance, rating 9 on the Mohs scale. Other properties include:

  • Relatively high melting point of 2050˚C 
  • Resistance to impact and corrosion
  • Inertness 
  • Durability under extreme pressure 
  • Thermal conductivity 
  • High heat resistance 
  • Transparent to wavelengths between 150nm (UV) and 5500nm (IR)
  • Chemical resistance 


It’s these properties that give synthetic Sapphire the edge against other advanced ceramic materials and advanced materials in general.

Production

There are various techniques for synthetic Sapphire growth and specific finishing effects. All methods for producing Sapphire include two basic steps, which are melting Alumina and cooling/solidifying it in such a way that it will leave the crystals aligned. There are six methods in total, all with their advantages and limitations. Selecting the right method should be done in collaboration with someone skilled in matching the fabrication technology and finishing process to the intended application. The finishing processes include shaping, slicing, grinding and polishing. 

Applications 

There is a wide range of applications for Sapphire, from miniature bearings to large missile nose domes. Here are some more examples of typical applications:

  • Semiconductor manufacturing: substrates, wafers, plasma containment tubes, chamber viewpoints, gas injector, lift pins 
  • Industrial: gas and chemical analysis, thermocouples, insulators, medical, rods, bearings, blanks, friction plates 
  • Optical: laser applications; high-performance synthetic Sapphire windows including UV, NIR, IR; NMR spectroscopy, lenses, prisms, blanks
  • Military and aerospace: Forward Looking Infrared (FLIR windows, guidance systems, radiometry, missile nose domes


What’s next?

Recent advances have led to the increasing of Sapphire parts, with tubes now up to 1000mm long, wafers approaching 300mm in diameter and domes over 200mm in diameter. This has given innovation a boost and has laid the path for new and exciting designs. The move toward near-net-shape crystal growth is also a catalyst for design flexibility. The potential of synthetic Sapphire has only just been unlocked.

For more information on synthetic Sapphire or Rubies, please contact a member of the team today via info@goodfellow.com