Fused silica has an extremely low coefficient of thermal expansion, which varies only slightly with temperature.
Fused Silica Mean Coefficient of Thermal Expansion1
0.52 x 10-6/K over the 5°C to 35°C temperature range
0.57 x 10-6/K over the 0°C to 200°C temperature range
0.48 x 10-6/K over the -100°C to 35°C temperature range
This material characteristic imparts fused silica a high resistance to thermal shock, and makes it an excellent material for applications that require the utmost in dimensional stability over a large temperature range.
For comparison, INVAR which has the lowest thermal expansion among all metals and alloys near room temperature has a mean coefficient of thermal expansion that is more than twice that of fused silica (1.3 x 10-6°/K over the 20°C to 100°C temperature range).
Thermal Conductivity
Fused silica is an excellent thermal insulator. Its thermal conductivity is only 1.38W/mºK (measured at 25ºC), which is one of the lowest for any solid.
For comparison this value is 100-fold lower than that of silicon (148W/mºK @ 25 C); and one eighth of that of INVAR (10.5 W/mºK @ 25 C).
1) Source: Präzisions Glas & Optik GmbH, Menden , Germany
