Furnace for making silicon carbide crystals

Claim 1

APPARATUS FOR THE PRODUCTION OF HEXAGONAL SILCON CARBIDE CRYSTALS, SAID CRYSTALS HAVING PARALLEL FACES, COMPRISING A CHAMBER HAVING A PERIPHERAL WALL OF GRAPHITE, SAID CHAMBER HAVING A LONGITUDINAL AXIS, CLOSURE MEANS FOR SAID CHAMBER, THERMAL INSULATION OUTSIDE OF AND SURROUNDING SAID CHAMBER, A HEAT SOURCE SURROUNDING AND EFFECTING HEATING OF SAID PERIPHERAL WALL TO A TEMPERATURE IN THE ORDER OF ABOUT 2300*C., A SOURCE OF SILICON VAPOR WITHIN THE CHAMBER, MEANS PROVIDING A CARBON SURFACE IN SAID CHAMBER THAT RECEIVES HEAT BY RADIATION FROM SAID WALL, AND BEING IN THE FORM OF A PLURALITY OF SPACED CONCENTRICALLY ARRANGED CYLINDERS FORMED OF CARBON, SAID CARBON SURFACE BEING DISPOSED RELATIVE TO THE PERIPHERAL WALL AND TO ONE SIDE OF AND GENERALLY PARALLEL TO SAID AXIS TO BE HEATED MORE ON ONE SIDE OF THE SURFACE THAN THE OTHER TO PRODUCE HOTTER AND COOLER SIDES ON THE OPPOSITE FACES OF THE SURFACE, HEAT SINK MEANS DISPOSED TO RECEIVE HEAT FLOWING FROM THE COOLER SIDE OF SAID SURFACE AND PROMOTE HEAT FLOW FROM THE SPACE BETWEEN SAID COOLER SIDE AND THE AXIS IN A DIRECTION GENERALLY PARALLEL TO THE AXIS, AND MEANS TO PROVIDE A GASEOUS ATMOSPHERE IN THE CHAMBERS.