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The HDS method

“Horizontal directional solidification method” created by Kh.S.Bagdasarov in 1964 was new radical idea of single crystal growth based on moving a crucible with the raw material and a single crystal seed in the horizontal direction. This method was created for the growth of large-size, Nd doped, high-perfect yttrium-aluminum garnet laser crystals. It turned out to be very efficient for sapphire growth too creating crystals with previously unseen surface areas. Using the HDS method issues of synthesis of large and especially large plate-form refractory leucosapphire single crystals were solved.

The HDS methods growth process consist of the following process’s

  • Seed (with any require crystal orientation) is installed at the front tip of the container which resembles a ship in a horizontal position
  • The raw sapphire material is placed in the container
  • The container is placed into a furnace
  • The growth process is done in a vaccum or inert atmosphere
  • During the growth process via a camera which is located on the top of the furnace, the process is being followed and diagnosed during the full duration of the growth process.
  • The melt is then slowly cooled
  • This method makes it possible to get large slabs with almost perfect edges and of any given crystallographic orientation: C-plane, M-plane, R-plane or A-plane
  • Bagdasarov sapphire has a very high optical quality and is suitable for very demanding optical, mechanical, RF and LED applications

The HDSM method allows to carry out repeated crystallization in case when additional chemical purification of the raw material is required. It is also possible to carry out a continuous crystallization process by directed shift of the crucible echelon through the crystallization zone. While realizing the HDSM method it is technically easy to create a controlled temperature field that is extremely necessary for growth of high-perfect large-size single crystals. This method makes it possible to get large slabs with almost perfect edges and of any given crystallographic orientation