Abstract: A quartz glass component having a projection on a flat face is manufactured by molding a quartz glass body at a high temperature and under high pressure. The heating temperature is set to a range of from 1800.degree. to 2000.degree. C. and slight pressure is applied by the female die which forms the projection, or pressure in a direction against gravity. The molding die includes a graphite frame surrounding a molding space formed by a female die and a receiving die sandwiching the quartz glass body in the graphite frame. The space between the receiving die and the female die is width-reducible, the compositions of the graphite frame and the two graphite dies are made to differ, the female die and receiving die contacting the quartz glass body during pressure molding have a plurality of gas-permeable micropores such as in sintered graphite for example and are formed by a high-purity graphite material having air permeability.

Abstract: A quartz glass crucible adapted for use in a process for pulling a single crystal semiconductor material having an opaque outer substrate of a quartz glass with a relatively high bubble content and an inner transparent glass layer which is substantially free from bubbles. The crucible is produced while the substrate is supported by a rotating mould by forming an atmosphere of high temperature gas and supplying a metered quantity of powders of quartz to the high temperature gas atmosphere to have the quartz powders molten at least partly and directed toward an inner surface of the substrate to be adhered thereon.

Abstract: A quartz glass crucible adapted for use in a process for pulling a single crystal semiconductor material having an opaque outer substrate of a quartz glass with a relatively high bubble content and an inner transparent glass layer which is substantially free from bubbles. The crucible is produced while the substrate is supported by a rotating mould by forming an atmosphere of high temperature gas and supplying a metered quantity of powders of quartz to the high temperature gas atmosphere to have the quartz powders molten at least partly and directed toward an inner surface of the substrate to be adhered thereon.