309results about How to "Small volume expansion" patented technology

A crucible with 22 inches or more in inner diameter, which has a small deformation of the body under exposure to abundant heat radiation during pulling a single crystal, and which has no practical problem, and a method of producing the same are disclosed. The method comprises the steps of: feeding first silicon dioxide powder along an inner surface of a rotating mold having a gas permeable wall to form a piled up layer of the first silicon dioxide powder; heating the piled up layer from the inside space of the mold to have the first silicon dioxide powder molten to provide the opaque outer layer as a substrate, while vacuum suction is effected through the wall; generating a high temperature gas atmosphere in an inside space of the substrate during or after the formation of the opaque outer layer; feeding second silicon dioxide powder into the high temperature gas atmosphere to have the second silicon dioxide powder molten at least partly; and directing the second silicon dioxide powder in an at least partly molten form toward an inner surface of the substrate to have the second silicon dioxide powder deposited on the inner surface of the substrate to thereby form the transparent inner layer thereon, the transparent inner layer being of a predetermined thickness and substantially free of bubbles.