In a known method for producing a quartz glass component, a crystal formation layer containing a crystallization promoter is produced on a coating surface of a base body of quartz glass. Starting therefrom, to provide a method for producing a quartz glass component of improved thermal strength and long-term stability which displays a comparatively small deformation particularly also in the case of rapid heating-up processes, it is suggested according to one aspect that a porous crystal formation layer containing amorphous SiO.sub.2 particles is produced with a mean thickness in the range of 0.1 to 5 mm, and that a substance which contains cesium and/or rubidium is used as the crystallization promoter.

A manufacturing method of a large-outer-diameter quartz crucible for a Czochralski (CZ) single crystal is provided. The manufacturing method is a vacuum arc method, and specifically includes: releasing a high-temperature arc with an electrode bundle composed of 2N+1 electrodes to fuse a crucible blank, and performing rapid cooling to form an initial quartz crucible product, where N is an integer greater than or equal to 2; the 2N+1 electrodes include one central main electrode and 2N auxiliary electrodes; the 2N auxiliary electrodes are equidistantly distributed on a circumference with the central main electrode as a center; the central main electrode is aligned at an axis of the crucible mold; the 2N auxiliary electrodes are connected to two phases of an industrial three-phase power, and the two phases are alternately arranged on the auxiliary electrodes; the central main electrode is connected to a remaining phase of the industrial three-phase power.

A manufacturing method of a large-outer-diameter quartz crucible for a Czochralski (CZ) single crystal is provided. The manufacturing method is a vacuum arc method, and specifically includes: releasing a high-temperature arc with an electrode bundle composed of 2N+1 electrodes to fuse a crucible blank, and performing rapid cooling to form an initial quartz crucible product, where N is an integer greater than or equal to 2; the 2N+1 electrodes include one central main electrode and 2N auxiliary electrodes; the 2N auxiliary electrodes are equidistantly distributed on a circumference with the central main electrode as a center; the central main electrode is aligned at an axis of the crucible mold; the 2N auxiliary electrodes are connected to two phases of an industrial three-phase power, and the two phases are alternately arranged on the auxiliary electrodes; the central main electrode is connected to a remaining phase of the industrial three-phase power.

A manufacturing method of a large-outer-diameter quartz crucible for a Czochralski (CZ) single crystal is provided. The manufacturing method is a vacuum arc method, and specifically includes: releasing a high-temperature arc with an electrode bundle composed of 2N+1 electrodes to fuse a crucible blank, and performing rapid cooling to form an initial quartz crucible product, where N is an integer greater than or equal to 2; the 2N+1 electrodes include one central main electrode and 2N auxiliary electrodes; the 2N auxiliary electrodes are equidistantly distributed on a circumference with the central main electrode as a center; the central main electrode is aligned at an axis of the crucible mold; the 2N auxiliary electrodes are connected to two phases of an industrial three-phase power, and the two phases are alternately arranged on the auxiliary electrodes; the central main electrode is connected to a remaining phase of the industrial three-phase power.

A manufacturing method of a large-outer-diameter quartz crucible for a Czochralski (CZ) single crystal is provided. The manufacturing method is a vacuum arc method, and specifically includes: releasing a high-temperature arc with an electrode bundle composed of 2N+1 electrodes to fuse a crucible blank, and performing rapid cooling to form an initial quartz crucible product, where N is an integer greater than or equal to 2; the 2N+1 electrodes include one central main electrode and 2N auxiliary electrodes; the 2N auxiliary electrodes are equidistantly distributed on a circumference with the central main electrode as a center; the central main electrode is aligned at an axis of the crucible mold; the 2N auxiliary electrodes are connected to two phases of an industrial three-phase power, and the two phases are alternately arranged on the auxiliary electrodes; the central main electrode is connected to a remaining phase of the industrial three-phase power.

Vacuum ultraviolet light with a wavelength of 200 nm or less is applied on the joining surfaces of first and second workpieces made from a crystal substrate and a glass substrate, or a glass substrate and a glass substrate from a light irradiation unit. The workpieces are conveyed to a workpiece cleaning and laminating mechanism by a conveyance mechanism, the joining surfaces are subjected to mega-sonic cleaning as needed, and the workpieces are aligned with the joining surfaces thereof facing each other, and laminated such that the joining surfaces are in contact with each other. After being laminated, the laminated workpieces are conveyed to a workpiece heating mechanism and heated to increase the workpiece temperature to a predetermined temperature, and this temperature is maintained until joining is completed. The laminated workpieces are brought into a thermally expanded state upon heating, and are joined in this state.

Vacuum ultraviolet light with a wavelength of 200 nm or less is applied on the joining surfaces of first and second workpieces made from a crystal substrate and a glass substrate, or a glass substrate and a glass substrate from a light irradiation unit. The workpieces are conveyed to a workpiece cleaning and laminating mechanism by a conveyance mechanism, the joining surfaces are subjected to mega-sonic cleaning as needed, and the workpieces are aligned with the joining surfaces thereof facing each other, and laminated such that the joining surfaces are in contact with each other. After being laminated, the laminated workpieces are conveyed to a workpiece heating mechanism and heated to increase the workpiece temperature to a predetermined temperature, and this temperature is maintained until joining is completed. The laminated workpieces are brought into a thermally expanded state upon heating, and are joined in this state.

Crystals having a modified regular tetrahedron shape are provided. Crystals preferably have four substantially identical triangular faces that define four truncated vertices and six chamfered edges. The six chamfered edges can have an average length of l, and an average width of w, and 8?l/w?9.5.

Crystals having a modified regular tetrahedron shape are provided. Crystals preferably have four substantially identical triangular faces that define four truncated vertices and six chamfered edges. The six chamfered edges can have an average length of l, and an average width of w, and 8?l/w?9.5.

An apparatus for manufacturing a silica glass crucible includes a rotating means for rotating a mold and a supply means for feeding a silica powder inside the mold, wherein the supply means has a feeding part for delivering the silica powder in a manner releasing it to fall to a position away from the inner wall surface of the mold inside the mold, and a dispersing part for changing, to one toward the inner wall surface side, at a fall position, the direction in which the silica powder fed from the feeding part moves, while also widening an angle at which the silica powder disperses toward the inner wall surface at the fall position. The apparatus is intended to allow a silica powder layer to be stably formed in the mold in a short period of time.