Czochralski Process (Crystal Pulling Technique)

Also known as the crystal pulling technique has a number of technical applications, since large crystals of good purity and optical homogeneity are obtained.

How gemstones are synthesized by czochralski process?

  • The source material is melted in a container (usually made of iridium) in an inert-gas atmosphere.
  • A rotating rod with a seed crystal is lowered until it touches the melt.
  • It is then slowly raised, allowing the molten source material, to solidify as the seed is slowly pulled from the melt.
  • The product obtained is a tabular boule which is virtually flawless.
  • Crystals which have lower melting points can be synthesized in the open, while high melting materials require a shield to control heat loss.

Gemstones synthesized by this method are:

  1. Synthetic Corundum (Synthetic Ruby and Synthetic Sapphire)
  2. Synthetic Alexandrite
  3. Yttrium Aluminium Garnet (various colours)
  4. Gadolinium Gallium Garnet (various colours)

When present characteristic inclusions include gas bubbles, curved lines and curved colour banding. Y.A.G. and G.G.G. have characteristic properties.