SCHOTT Technical Glasses

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4. Electrical Properties
For more than 70 years, SCHOTT has been developing vacuum-tight
assemblies of glass and metal that enable electrical signals to pass
through the walls of hermetically sealed packages, relays, for example.
As electrically highly insulating materials, glasses are used
in electrical engineering and electronics for the production
of high-vacuum tubes, lamps, electrode seals, hermetically
encapsulated components, high-voltage insulators, etc.
Moreover, glasses may be used as insulating substrates of
electrically conducting surface layers (surface heating elements
and data displays).
4.1 Volume resistivity
Electrical conductivity in technical silicate glasses is, in general,
a result of the migration of ions – mostly alkali ions.
At room temperature, the mobility of these ions is usually
so small that the volume resistivities with values above
10 15 Ω cm (10 13 Ω m) are beyond the range of measurement.
The ion mobility increases with increasing temperature.
Besides the number and nature of the charge carriers,
structural effects of other components also influence the
volume resistivity and its temperature relationship. An
Arrhenius law which is used in glass science sometimes also
called Rasch-Hinrichsen law applies to this relationship at
temperatures below the transformation range:
lg ρ = A – B/T
ρ = electrical volume resistivity
A, B = specific glass constants
T = absolute temperature