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.