A glass composition includes a base glass portion comprising: 65-75 wt % SiO.sub.2; 5-15 wt % CaO; 0-5 wt % MgO; 0-5 wt % K.sub.2O; 10-14 wt % Na.sub.2O; and 1-5 wt % Al.sub.2O.sub.3; wherein the glass composition has a ratio of Na.sub.2O to Al.sub.2O.sub.3 is in the range of 9.5-12.5 wt %/wt %.

A glass element has, per kg of glass, 50 or fewer inclusions having a size of 2 μm to 10 μm. The glass element can be made of borosilicate glass.

A glass article is designed at least in part in the form of a glass tube element including at least one shell which encloses at least one lumen. For at least one light transmission analysis of the glass article, a ratio of an average amplitude transmission factor and a specific amplitude transmission factor is greater than 1.00001.

Lithium silicate-low quartz glass ceramics are described which are characterized by a combination of very good mechanical and optical properties and can therefore be used in particular as restoration material in dentistry.

A glass-ceramic includes SiO2 in a range of 40 mol. % to 80 mol. %; Al.sub.2O.sub.3 in a range of 5 mol. % to 20 mol. %; MgO in a range of 5 mol. % to 20 mol. %; and at least one of B.sub.2O.sub.3, ZnO, and TiO.sub.2, each in a range of 0 mol. % to 10 mol. %, such that the glass-ceramic further comprises a magnesium aluminosilicate crystalline phase at a concentration in a range of 5 wt. % to 80 wt. % of the glass-ceramic.

An alkali free glass has an average coefficient of thermal expansion at 50 to 350° C. of 30×10.sup.−7 to 43×10.sup.−7/° C., a Young's modulus of 88 GPa or more, a strain point of 650 to 725° C., a temperature T.sub.4 at which a viscosity reaches 10.sup.4 dPa.Math.s of 1,290° C. or lower, a glass surface devitrification temperature (T.sub.c) of T.sub.4+20° C. or lower, and a temperature T.sub.2 at which the viscosity reaches 10.sup.2 dPa.Math.s of 1,680° C. or lower. The alkali free glass contains, as represented by mol % based on oxides, 62 to 67% of SiO.sub.2, 12.5 to 16.5% of Al.sub.2O.sub.3, 0 to 3% of B.sub.2O.sub.3, 8 to 13% of MgO, 6 to 12% of CaO, 0.5 to 4% of SrO, and 0 to 0.5% of BaO. MgO+CaO+SrO+BaO is 18 to 22%, and MgO/CaO is 0.8 to 1.33.

A silica-titania glass substrate comprising: (i) a composition comprising 5 weight percent to 10 weight percent TiO.sub.2; (ii) a coefficient of thermal expansion (CTE) at 20° C. in a range from −45 ppb/K to +20 ppb/K; (iii) a crossover temperature (Tzc) in a range from 10° C. to 50° C.; (iv) a slope of CTE at 20° C. in a range from 1.20 ppb/K.sup.2 to 1.75 ppb/K.sup.2; (v) a refractive index variation of less than 140 ppm; and (vi) 600 ppm OH group concentration or greater. The substrate can have a mass of 1 kg or greater and less than 0.05 gas inclusions per cubic inch via a method comprising (i) forming the substrate from soot particles comprising SiO.sub.2 and TiO.sub.2, and (ii) subjecting the substrate to an environment having an elevated temperature and an elevated pressure for a period of time until the substrate comprises less than 0.05 gas inclusions per cubic inch.

The present invention relates to a glass ceramic having improved thermal expansion characteristics and to the use thereof in a precision component.

The present invention relates to a glass ceramic having improved thermal expansion characteristics and to the use thereof in a precision component.

The invention relates to a process for preparing a quartz glass body comprising the process steps i.) Providing a silicon dioxide granulate, ii.) Making a glass melt from the silicon dioxide granulate in a melting crucible, and iii.) Making a quartz glass body from at least a part of the glass melt, wherein the melting crucible is comprised in an oven and is made of at least one material comprising tungsten or molybdenum or a combination thereof. The invention further relates to a quartz glass body which can be obtained by this process. Further, the invention relates to a light guide, an illuminant and a formed body, each of which can be obtained by processing the quartz glass body further.