Growing of large-sized high-quality sapphire by the Kyropoulos method

A transparent large-scale sapphire approximately 250 mm in diameter and about 30 kg in weight were grown by the Kyropoulos technique along the crystallographic direction. An analysis of the crystallization front shape at various stages of crystal growth was carried out. The dislocation structure was studied by selective chemical etching and X-ray diffraction, the thermoplastic stresses were assessed in large boule using the polarized light methods. The crack resistance was determined using the Vickers method, the optical absorption in sapphire was also investigated.