Schott Glas

Schott Ag

Gerhard Westenberger

Burkhard Speit

Ralf Jedamzik

Axel Engel

Clemens Kunisch

Peter Fischer

A method is provided for determining the thermal expansion of a low thermal expansion material with very high accuracy of at most +/&#x2212;3 ppb/K or less and/or with a reproducibility of at most +/&#x2212;1 ppb/K or less. A measuring device is also provided that includes an advanced push rod dilatometer.

High-precision method for determining thermal expansion

Glass for rigid disk substrates

The glasses used for making rigid disk substrates have the following composition (based on the % by weight of the oxides): SiO.sub.2, 40 to 60; Al.sub.2 O.sub.3, 5 to 20; B.sub.2 O.sub.3, 0 to 5; Li.sub.2 O, 0 to 10; Na.sub.2 O, 0 to 12, with the proviso that Li.sub.2 O+Na.sub.2 O 5 to 12; K.sub.2 O, 0 to 5; MgO, 0 to 20; CaO, 0 to 6, with the proviso that MgO+CaO, 4 to 20,SrO+BaO, 0 to 10; Zr.sub.2 O, 0 to 5; TiO.sub.2, 0 to 5; CeO.sub.2, 0 to 1; La.sub.2 O.sub.3, 0 to 10; Fe.sub.2 O.sub.3, 0 to 10; Nb.sub.2 O.sub.5, 0 to 10; V.sub.2 O.sub.5, 0 to 15, with the proviso that TiO.sub.2 +ZrO.sub.2 +La.sub.2 O.sub.3 +Fe.sub.2 O.sub.3 +Nb.sub.2 O.sub.3 +V.sub.2 O.sub.5 .gtoreq.8, As.sub.2 O.sub.3 +Sb.sub.2 O.sub.3 +F, 0.1 to 1; or, SiO.sub.2, 10 to 30; Al.sub.2 O.sub.3, 0 to 5; B.sub.2 O.sub.3, 0 to 8; Li.sub.2 O, 0 to 8; Na.sub.2 O, 1 to 10, with the proviso that Li.sub.2 O+Na.sub.2 O, 5 to 10; K.sub.2 O, 0 to 3; MgO, 0 to 12; CaO, 0 to 15, with the proviso that MgO+CaO,10 to 15, SrO+BaO, 0 to 8; Zr.sub.2 O, 0 to 8; TiO.sub.2, 10 to 25; La.sub.2 O.sub.3, 0 to 10; Nb.sub.2 O.sub.5, 10 to 18; V.sub.2 O.sub.5, 0 to 20; CeO.sub.2, 0 to 1; As.sub.2 O.sub.3 +Sb.sub.2 O.sub.3 +F, 0.1 to 1. Both types or groups of glasses fulfill the following inequality formulae (1):

Growing community of inventors

Mainz, Germany

Gerhard Westenberger