Powdered silica, silica container, and method for producing them

A powdered silica for producing a silica container, wherein the powdered silica has particle diameter of 10 to 1000 μm, contains Ca, Sr, and Ba with the total concentration of 50 to 5000 ppm by weight, and releases hydrogen molecules with the amount of 3×1016 to 3×1019 molecules/g upon heating at 1000° C. under vacuum.

A silica container arranged with a substrate, having a rotational symmetry, comprised of mainly a silica, and containing gaseous bubbles at least in its peripheral part, and an inner layer, formed on an inner surface of the substrate and comprised of a transparent silica glass;

• wherein the substrate contains Li, Na, and K with the total concentration of 50 or less ppm by weight, and the inner layer contains Ca, Sr, and Ba with the total concentration of 50 to 5000 ppm by weight and shows a light transmittance of 91.8 to 93.2% at a light wavelength of 600 nm for a cut-out sample having 10 mm thickness.

A method for producing a silica container arranged with a substrate, having a rotational symmetry, comprised of mainly a silica, and containing gaseous bubbles at least in its peripheral part, and an inner layer, formed on an inner surface of the substrate and comprised of a transparent silica glass;

• wherein a powdered silica, having particle diameter of 10 to 1000 μm, containing Ca, Sr, and Ba with the total concentration of 50 to 5000 ppm by weight, and releasing hydrogen molecules with the amount of 3×1016 to 3×1019 molecules/g upon heating at 1000° C. under vacuum, is prepared at least as a powdered raw material for forming the inner layer, and then the inner layer is formed on an inner surface of the substrate by using the powdered silica as the powdered raw material for forming the inner layer.