Abstract: An epitaxy bell of transparent fused silica is provided with a flanged, thick-walled tubular piece of transparent fused silica on the side on which a process gas is exhausted. The wall thickness of the constricted portion of the bell is increased toward the transparent fused silica tubular piece.

Abstract: A method is described for the production of porous bodies from vitreous silica without the use of tools. Vitreous silica wool and/or threads are wound in layers on a form. After the coil has attained a certain minimum thickness, the threads of each succeeding layer are permanently bonded by heating the threads of the preceding layer at the points where the threads cross. The form is removed, and then the threads on the inside of the body are bonded together.The bodies are used for the production of high-purity blocks of silicon for solar cells.

Abstract: Quartz glass element, such as a diffusion tube useful in the production of semiconductor elements, capable of forming an outer layer of uniformly fine crystalline silica such as cristobalite or tridymite when heated to a temperature at which such crystalline silica forms containing crystallization promoting nuclei having a rate of diffusion in quartz glass less than that of sodium at elevated temperatures. Such nuclei are preferably present in the outer half of the element wall. When the quartz glass element is exposed to elevated temperatures, the nuclei promotes the formation of the outer layer of uniformly fine crystalline silica which imparts thermal dimensional stability for extended periods of use at elevated temperatures.

Abstract: A crucible of pure transparent silica glass or pure translucent or opaque silica glass for the production of monocrystals used in making semiconductor elements which includes a hollow cylindrical part and a welded-on head. The head end of the hollow cylindrical part is formed from a tube with a head margin portion constricted towards the tube axis which is formed by shaping one end of the tube. A plate is welded into the aperture formed by the constricted head margin portion and has an area equal to at least one-tenth and at most four-fifths of the total head area made up by the head margin portion and the head.