One aspect relates to a process for the preparation of a quartz glass body, including providing a silicon dioxide granulate, wherein the silicon dioxide granulate was made from pyrogenic silicon dioxide powder and the silicon dioxide granulate has a BET surface area in a range from 20 to 40 m.sup.2/g, making a glass melt out of silicon dioxide granulate in an oven and making a quartz glass body out of at least part of the glass melt. The oven has at least a first and a further chamber connected to one another via a passage. The temperature in the first chamber is lower than the temperature in the further chambers. On aspect relates to a quartz glass body which is obtainable by this process. One aspect relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

One aspect relates to a process for the preparation of a quartz glass body, including providing a silicon dioxide granulate, wherein the silicon dioxide granulate was made from pyrogenic silicon dioxide powder and the silicon dioxide granulate has a BET surface area in a range from 20 to 40 m.sup.2/g, making a glass melt out of silicon dioxide granulate in an oven and making a quartz glass body out of at least part of the glass melt. The oven has at least a first and a further chamber connected to one another via a passage. The temperature in the first chamber is lower than the temperature in the further chambers. On aspect relates to a quartz glass body which is obtainable by this process. One aspect relates to a light guide, an illuminant and a formed body, which are each obtainable by further processing of the quartz glass body.

The present invention relates to a method for evaluating the thermal expansion properties of a titania-containing glass body. On the basis of measured values, obtained at a certain temperature, for a physical parameter that changes depending on the titania concentration and a physical parameter that changes depending on the fictive temperature, the thermal expansion coefficient of the titania-containing silica glass body and the slope of the thermal expansion coefficient are calculated using a linear relational expression represented by a plurality of physical properties. The thermal expansion properties of the titania-containing silica glass body are evaluated on the basis of the calculated thermal expansion coefficient and thermal expansion coefficient slope.

A quartz glass crucible (1) has a structure wherein a peak of a distribution of a total concentration of Na, K, and Ca in a depth direction from an inner surface (10i) of the crucible is present at a position deeper than the inner surface (10i). In an exemplary embodiment, the quartz glass crucible is capable of improving the yield of a silicon single crystal by suppressing peeling-off of brown rings.

A quartz glass crucible (1) has a structure wherein a peak of a distribution of a total concentration of Na, K, and Ca in a depth direction from an inner surface (10i) of the crucible is present at a position deeper than the inner surface (10i). In an exemplary embodiment, the quartz glass crucible is capable of improving the yield of a silicon single crystal by suppressing peeling-off of brown rings.

A quartz container manufacturing method and a forming apparatus, relating to the solar photovoltaic technical field, and providing a mold comprising a top cylinder and a mold bottom; during formation of a container blank, when the mold forms a first included angle with a horizontal plane and the mold is rotated at a first rotation speed, the source material forms a first blank on the inner wall of the top cylinder; when the mold forms a second included angle with the horizontal plane and the mold is rotated at a second rotation speed, the source material forms a second blank on the inner wall of the mold bottom; a quartz container is manufactured from a container blank composed of the first blank and the second blank.

A quartz container manufacturing method and a forming apparatus, relating to the solar photovoltaic technical field, and providing a mold comprising a top cylinder and a mold bottom; during formation of a container blank, when the mold forms a first included angle with a horizontal plane and the mold is rotated at a first rotation speed, the source material forms a first blank on the inner wall of the top cylinder; when the mold forms a second included angle with the horizontal plane and the mold is rotated at a second rotation speed, the source material forms a second blank on the inner wall of the mold bottom; a quartz container is manufactured from a container blank composed of the first blank and the second blank.

The present invention relates to a silica glass including bublles in the number of 1×10.sup.7/cm.sup.3 to 1×10.sup.15/cm.sup.3 and having a density of 0.5 g/cm.sup.3 to 1.95 g/cm.sup.3. The present invention also relates to a method for producing a silica glass, including: a step of depositing SiO.sub.2 fine particles generated by flame hydrolysis of a silicon compound, to obtain a silica glass porous body; a step of heating and sintering the silica glass porous body in an inert gas atmosphere, to obtain a silica glass dense body; and a step of performing a foaming treatment to heat the silica glass dense body under a reduced pressure condition.

The present invention relates to a silica glass including bublles in the number of 1×10.sup.7/cm.sup.3 to 1×10.sup.15/cm.sup.3 and having a density of 0.5 g/cm.sup.3 to 1.95 g/cm.sup.3. The present invention also relates to a method for producing a silica glass, including: a step of depositing SiO.sub.2 fine particles generated by flame hydrolysis of a silicon compound, to obtain a silica glass porous body; a step of heating and sintering the silica glass porous body in an inert gas atmosphere, to obtain a silica glass dense body; and a step of performing a foaming treatment to heat the silica glass dense body under a reduced pressure condition.

A silica glass crucible includes a cylindrical side wall portion, a curved bottom portion, and a corner portion that is provided between the side wall portion and the bottom portion and has a higher curvature than a curvature of the bottom portion, in which a first region provided from a crucible inner surface to a middle in a thickness direction, a second region that is provided outside the first region in the thickness direction and has a different strain distribution from the first region, and a third region that is provided outside the second region in the thickness direction and up to the crucible outer surface and has a different strain distribution from the second region, are provided, and internal residual stresses of the first region and the third region are compressive stresses, whereas an internal residual stress of the second region includes a tensile stress.