The invention relates to glass articles, such as for example glass tubes or flat glasses, where the material at the surface by a targeted process control has gradient material properties which in turn result in a compressive prestress of the surface. The invention also relates to a method for the production of the glass articles as well as their use.

A photodarkening-resistant ytterbium-doped quartz optical fiber and a method for prpearing such a fiber are provided. Glass of a photodarkening-resistant ytterbium-doped quartz optical fiber core rod includes at least Yb.sub.2O.sub.3, Al.sub.2O.sub.3, P.sub.2O.sub.5, SiO.sub.2. The proportions of Yb.sub.2O.sub.3, Al.sub.2O.sub.3, and P.sub.2O.sub.5 in the entire substance are Yb.sub.2O.sub.3: 0.05-0.3 mol %, Al.sub.2O.sub.3: 1-3 mol %, and P.sub.2O.sub.5: 1-5 mol %, respectively. In the preparation method for the photodarkening-resistant ytterbium-doped quartz optical fiber, a sol-gel method and an improved chemical vapor deposition method are combined. By using the molecular-level doping uniformity and the low preparation loss thereof respectively, ytterbium ions, aluminum ions and phosphorus ions are effectively doped in a quartz matrix, thereby effectively solving the problems in the optical fiber of high loss, photodarkening caused by cluster or the like, and a central refractive index dip.

The invention relates to glass articles, such as for example glass tubes or flat glasses, where the material at the surface by a targeted process control has gradient material properties which in turn result in a compressive prestress of the surface. The invention also relates to a method for the production of the glass articles as well as their use.

A multilayer coil component includes a component element assembly in which an inner conductor is disposed and an outer electrode disposed on the surface of the component element assembly. The component element assembly includes a first dielectric glass layer in which the inner conductor is embedded and second dielectric glass layers that are thin layers disposed on respective principal surfaces of the first dielectric glass layer. The primary component of each of the first dielectric glass layer and the second dielectric glass layers is formed of a glass material and has a filler component containing at least quartz, and the second dielectric glass layers have a lower quartz content than the first dielectric glass layer.

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.

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 glass composition comprising: Al.sub.2O.sub.3, ZnO, and SiO.sub.2; TiO.sub.2, in the amount of at least 10 mol % and not greater than 20 mol %; and alkaline metal oxide selected from the group consisting of MgO, CaO, SrO, BaO, or any combination thereof, such that the molar sum of MgO, CaO, SrO, BaO, and ZnO, in the amount in the glass composition is least 20 mol % and not greater than 35 mol %, and such that: the amount of BaO is 0 to 10 mol %; the amount of MgO is 0 to 10 mol %
the amount of CaO is 0 to 10 mol %, and the molar sum of CaO and MgO in the glass composition is less than 12.5 mol %; and rare earth metal oxides (ΣRE.sub.mO.sub.n), in the amount of at least 1.5 mol % and not greater than 10 mol %; alkali metal oxides (ΣAlk.sub.2O), in the amount of greater than or equal to 0 mol % and less than or equal to 5 mol %; and not greater than 5 mol % of other components; and wherein −5 mol %≤Al.sub.2O.sub.3 (mol %)−1.5 ΣRE.sub.mO.sub.n (mol %)−ΣAlk.sub.2O (mol %)≤+5 mol %.

A photodarkening-resistant ytterbium-doped quartz optical fiber and a method for preparing such a fiber are provided. Glass of a photodarkening-resistant ytterbium-doped quartz optical fiber core rod includes at least Yb.sub.2O.sub.3, Al.sub.2O.sub.3, P.sub.2O.sub.5, SiO.sub.2. The proportions of Yb.sub.2O.sub.3, Al.sub.2O.sub.3, and P.sub.2O.sub.5 in the entire substance are Yb.sub.2O.sub.3: 0.05-0.3 mol %, Al.sub.2O.sub.3: 1-3 mol %, and P.sub.2O.sub.5: 1-5 mol %, respectively. In the preparation method for the photodarkening-resistant ytterbium-doped quartz optical fiber, a sol-gel method and an improved chemical vapor deposition method are combined. By using the molecular-level doping uniformity and the low preparation loss thereof respectively, ytterbium ions, aluminum ions and phosphorus ions are effectively doped in a quartz matrix, thereby effectively solving the problems in the optical fiber of high loss, photodarkening caused by cluster or the like, and a central refractive index dip.

The invention relates to an optical fiber preform (20) comprising a primary preform (21) and one or more purified silica-based overclad layers (22) surrounding said primary preform (21), the purified silica-based overclad layers (22) comprising lithium and aluminium, and having a ratio between lithium concentration [Li] and aluminium concentration [Al] satisfying the following inequality:
1×10.sup.−3≤[Li]/[Al]≤20×10.sup.−3.