Abstract: To provide opaque quartz glass having no water absorbing properties and being excellent in infrared light shielding properties, and a method for its production. In the production of opaque quartz glass of the present invention, a fine amorphous silica powder and a pore forming agent are mixed, then molded and heated at a predetermined temperature, to obtain opaque quartz glass wherein contained pores are closed pores, the average pore size of pores is from 5 to 20 ?m, and the content density of pores is high, whereby the heat shielding properties are high.

Abstract: To provide opaque quartz glass having no water absorbing properties and being excellent in infrared light shielding properties, and a method for its production. In the production of opaque quartz glass of the present invention, a fine amorphous silica powder and a pore forming agent are mixed, then molded and heated at a predetermined temperature, to obtain opaque quartz glass wherein contained pores are closed pores, the average pore size of pores is from 5 to 20 ?m, and the content density of pores is high, whereby the heat shielding properties are high.

Abstract: Fused silica glass having an internal transmittance of UV with 245 nm wavelength, being at least 95% at 10 mm thickness, a OH content of not larger than 5 ppm, and a content of Li, Na, K, Mg, Ca and Cu each being smaller than 0.1 ppm. Preferably the glass has a viscosity coefficient at 1215° C. of at least 1011.5 Pa·s; and a Cu ion diffusion coefficient of not larger than 1×10?10 cm2/sec in a depth range of greater than 20 ?m up to 100 ?m, from the surface, when leaving to stand at 1050° C. in air for 24 hours. The glass is made by cristobalitizing powdery silica raw material; then, fusing the cristobalitized silica material in a non-reducing atmosphere. The glass exhibits a high transmittance of ultraviolet, visible and infrared rays, has high purity and heat resistance, and exhibits a reduced diffusion rate of metal impurities, therefore, it is suitable for various optical goods, semiconductor-production apparatus members, and liquid crystal display production apparatus members.

Abstract: Fused silica glass having an internal transmittance of UV with 245 nm wavelength, being at least 95% at 10 mm thickness, a OH content of not larger than 5 ppm, and a content of Li, Na, K, Mg, Ca and Cu each being smaller than 0.1 ppm. Preferably the glass has a viscosity coefficient at 1215° C. of at least 1011.5 Pa·s; and a Cu ion diffusion coefficient of not larger than 1×10?10 cm2/sec in a depth range of greater than 20 ?m up to 100 ?m, from the surface, when leaving to stand at 1050° C. in air for 24 hours. The glass is made by crystobalitizing powdery silica raw material; then, fusing the crystobalitized silica material in a non-reducing atmosphere. The glass exhibits a high transmittance of ultraviolet, visible and infrared rays, has high purity and heat resistance, and exhibits a reduced diffusion rate of metal impurities, therefore, it is suitable for various optical goods, semiconductor-production apparatus members, and liquid crystal display production apparatus members.

Abstract: A high-purity transparent silica glass containing Fe, Na and K impurities each in an amount of 0.01-0.3 ppm, and an OH group in an amount of 0-3 ppm; among the Fe impurities, the content of metallic Fe having a valency of +0 being not larger than 0.1 ppm. This transparent silica glass exhibits, even when it is maintained at 900-1,400.degree. C. for at least 20 hours, an extinction coefficient of not larger than 0.009 at a wavelength of 400 nm, and does not become colored as visually examined. The silica glass is made by a process wherein powdery silica filled in a mold cavity is melted at 1,700.degree. C. or higher, characterized in that the melting is conducted in a graphite mold having a porous high-purity graphite layer provided on the mold inner surface so that the filled silica is not contacted with the mold; said porous layer having a bulk density of 0.1-1.5 g/cm.sup.3, and the content of each of Fe, Na and K impurities in the porous layer being not larger than 1 ppm.

Abstract: A fluorescent substance of which main component is comprised from 32 mol % to 35 mol % of silicon element and from 68 mol % to 65 mol % of oxygen element, and in which includes from 10 ppm to 1 wt % of silicon carbide and silicon nitride as an activator. And, a manufacturing method of the fluorescent substance by hydrolyzing silicon alkoxide by using alkali or acid catalyzer under the presence of carbon, and by heat treating the obtained precursor at the temperature of 500.degree. C. to 900.degree. C.

Abstract: An achromatic lens for ultraviolet rays constituted by (A) high-purity silica glass having a purity of 99.9% or more, or fluorine-containing, high-purity silica glass having a purity of 99.9% or more; and (B) silica glass containing germanium dioxide or silica glass containing germanium dioxide and boron oxide.