Abstract: A furnace for growing sapphire crystal in which the furnace comprises a furnace housing; a hot zone which comprises insulation and a heater which are both accommodated within the furnace housing; a crucible located within the hot zone and the crucible has an opening. Either a crucible lid covers the opening of the crucible, and the crucible lid has a first conduit which extends therefrom or a crucible enclosure surrounds at least a side wall and a top portion of the crucible and the crucible enclosure is impermeable to at least carbon preventing carbon contamination of a melt contained within the crucible.

Abstract: A method for producing growth-axis oriented single crystal sapphire cores or near-net cores is provided. According to the method, a boule is grown on a desired growth axis having a first axial end and a second axial end. An orientation of a plane normal to the desired growth axis with respect to the boule is determined. The boule is then cored in a direction perpendicular to the plane to produce at least one growth-axis oriented single crystal sapphire core, or the boule is outer-diameter-grinded the boule to form a single crystal sapphire near-net core.