The invention relates to a glass or glass-ceramic plate comprising a glass or glass-ceramic substrate coated with a metal-oxide-based coating, characterized in that said coating has a coverage rate of 25% to 90% and the coated plate has a roughness RSm less than or equal to 300 m, preferably less than or equal to 250 m.

An optical fiber having a reduced attenuation includes a silica glass core and a silica glass cladding. The silica glass core has substantially no germanium and includes a first core and a second core. The second core encloses the first core, the refractive index of the second core is larger than the refractive index of the first core, and the average value of halogen concentration of the second core is 5000 ppm or more. The silica glass cladding surrounds the second core and contains substantially no germanium. The refractive index of the cladding is smaller than the refractive index of the first core.

An optical fiber having a reduced attenuation includes a silica glass core and a silica glass cladding. The silica glass core has substantially no germanium and includes a first core and a second core. The second core encloses the first core, the refractive index of the second core is larger than the refractive index of the first core, and the average value of halogen concentration of the second core is 5000 ppm or more. The silica glass cladding surrounds the second core and contains substantially no gemianium. The refractive index of the cladding is smaller than the refractive index of the first core.

A doped silica-titania glass article is provided that includes a glass article having a glass composition comprising (i) a silica-titania base glass, (ii) a fluorine dopant, and (iii) a second dopant. The fluorine dopant has a concentration of fluorine of up to 5 wt. % and the second dopant comprises one or more oxides selected from the group consisting of Al, Nb, Ta, B, Na, K, Mg, Ca and Li oxides at a total oxide concentration from 50 ppm to 6 wt. %. Further, the glass article has an expansivity slope of less than 0.5 ppb/K.sup.2 at 20 C. The second dopant can be optional. The composition of the glass article may also contain an OH concentration of less than 100 ppm.

Ultralow expansion titania-silica glass. The glass has high hydroxyl content and optionally include one or more dopants. Representative optional dopants include boron, alkali elements, alkaline earth elements or metals such as Nb, Ta, Al, Mn, Sn Cu and Sn. The glass is prepared by a process that includes steam consolidation to increase the hydroxyl content. The high hydroxyl content or combination of dopant(s) and high hydroxyl content lowers the fictive temperature of the glass to provide a glass having a very low coefficient of thermal expansion (CTE), low fictive temperature (T.sub.f), and low expansivity slope.

The present invention provides a tempered glass sheet including as a glass composition, in terms of mol %, 50% to 80% of SiO.sub.2, 7% to 25% of Al.sub.2O.sub.3, 0% to 15% of B.sub.2O.sub.3, 0% to 15% of Li.sub.2O, 0% to 25% of Na.sub.2O, 0% to 10% of K.sub.2O, 0% to 15% of MgO, 0% to 10% of CaO, 0% to 10% of SrO, 0% to 10% of BaO, 0% to 10% of ZnO, 0% to 15% of P.sub.2O.sub.5, 0% to 10% of TiO.sub.2, 0% to 10% of ZrO.sub.2, and 0% to 0.30% of SnO.sub.2, having a value of [B.sub.2O.sub.3]+[MgO]+[CaO] of from 0.1% to 30%, and having a value of ([Li.sub.2O]+[Na.sub.2O]+[K.sub.2O])/[Al.sub.2O.sub.3] of from 0.5 to 2.0.

Provided is a method for producing a glass substrate that can reduce the dimensional change during heat treatment while avoiding shortening of facilities' service lives. A method for producing a glass substrate includes melting and forming a glass raw material to produce a glass substrate having a strain point of 690 to 750 C., wherein an average cooling rate in a temperature range from (an annealing point plus 150 C.) to (the annealing point minus 200 C.) in a cooling process during the forming is adjusted to 100 to 400 C./min to obtain the glass substrate having a degree of thermal contraction of 15 ppm or less when subjected to a heat treatment at 500 C. for an hour.

A manufacturing method of a quartz glass crucible includes: producing a quartz glass crucible by arc-melting raw material quartz powder deposited on an inner surface of a rotating mold; washing an inner surface of the quartz glass crucible with pure water thereby reducing a total concentration of Na, K, and Ca contained in a silica glass around the inner surface as compared to that before washing; and etching the inner surface with washing liquid containing hydrofluoric acid.

The present disclosure relates to plasma-resistant glass, an inner chamber component for a semiconductor manufacturing process, and methods for manufacturing the glass and the component, and specifically, to plasma-resistant glass, an inner chamber component for a semiconductor manufacturing process, and methods for manufacturing the glass and the component, wherein the contents of plasma-resistant glass components in the plasma-resistant glass are adjusted and SrO is added to achieve a lower melting temperature, the thermal expansion coefficient of the plasma-resistant glass is reduced to prevent damage from thermal shock during high-temperature use, and the plasma-resistant glass has improved light transmittance and durability.

Disclosed herein is a glass composition including, based on a total weight of the glass composition, 49 wt % to 59 wt % of SiO.sub.2, 9.5 wt % to 14.5 wt % of Al.sub.2O.sub.3, 19 wt % to 35 wt % of B.sub.2O.sub.3, 2 wt % to 5 wt % of CaO, 0.25 wt % to 3 wt % of ZnO, 0 wt % to 1 wt % of MgO, 0 wt % to 1 wt % of TiO.sub.2, 0 wt % to 3 wt % of ZrO.sub.2, and 0.1 wt % to 3.5 wt % of MnO. Also disclosed herein are a glass fiber and a glass article which include the glass composition.