Method and apparatus for growing sapphire single crystals

An apparatus for growing sapphire single crystals, comprising:

• a furnace surrounding a crucible for heating the crucible, wherein the furnace is thermally insulating from the surrounding air so as to cause an internal temperature of the furnace to rise up to more than a melting temperature of a sapphire scrap;
• a crucible having a rectangular cross-sectional shape, wherein the crucible has a bottom, a front horizontal wall, a back horizontal wall, and two end walls and a horizontal wall:end wall aspect ratio more than 1.5:1, wherein the crucible can be disposed within the furnace so as to allow the sapphire scrap to be melted therein and allow a single crystal to be grown long from a seed crystal therein;
• a plurality of heaters disposed at the outside of the crucible, adjacent to the walls of the crucible, so as to melt the sapphire scrap;
• and cooling means disposed at the bottom of the crucible so as to prevent the seed crystal from being completely melted,
• wherein the plurality of heaters are disposed along the horizontal walls of the crucible to create three to six horizontal and divided heating zones, wherein each of the divided heating zones are independently controlled so as to uniformly maintain temperature along the horizontal walls of the crucible, and
• wherein each heating zone comprises (a) a pair of lateral heating elements which are disposed at the front and back horizontal walls of the crucible, wherein each heating element is connected to an electrode and the corresponding heating element, and (b) a connecting heating element for interconnecting each pair of lateral heating elements;
• and
• wherein the crucible is arranged to accommodate a seed crystal that can extend in a c-axial direction so that a sapphire single crystal can be grown in the c-axial direction.