3.4.1.2 Steatite
Steatite is a ceramic material based on
natural raw materials and consists mainly of soapstone (Mg(Si4O10)(OH)2),
a natural magnesium silicate, with the addition of clay and
feldspar or barium carbonate. Steatite is usually sintered
to a high density.
The type of flux used influences the electrical properties
of this material, leading to a distinction between normal
steatite and special steatite, also known as high-frequency
steatite.
Special steatite is defined in international standards as
steatite with a low loss factor, and is not only used in low-loss
high-frequency parts, but because of its excellent workability
it is also used for the manufacture of components with thin,
constant thickness. This allows thermally induced mechanical
stresses to be controlled.
This material also permits the economical manufacture of products
with very small tolerances due to its low shrinkage during
sintering. It is also less abrasive to tools than any other
ceramic, making it particularly suited to dry pressing.
Figure 4: Steatite (C 221) surface with firing
skin
Special steatite possesses excellent mechanical
and dielectric properties, and has been used for more than
90 years in various applications in electrical engineering,
for electronic parts and in heat engineering. Typical applications
include sockets, control housings, insulating beads, low-voltage
power fuses and base plates.
For special applications such as heating cartridges, porous
steatite is often used, since it can be easily machined even
after sintering, and has a very good thermal shock resistance.
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