3 Ceramic Materials
The terminology currently in general use
in ceramic engineering and having industrial significance
will be presented here.
Ceramic, as a materials
definition, involves concepts that have developed over history
due to the diversity of the applications and raw materials
used. Many systematic national definitions are slowly beginning
to find a common basis as a result of international scientific
cooperation, industrial standardisation and international
Very generally defined:
Ceramic materials are inorganic
and non-metallic. They are generally moulded from a mass of
raw material at room temperature, and gain their typical physical
properties through a high temperature firing process. (See
also "High-performance ceramics".)
In contrast, the Anglo-Saxon term "ceramics"
also often includes glass, enamel, glass-ceramic, and inorganic
cementitious materials (cement, plaster and lime).
The German ceramics industry also distinguishes
between coarse and fine ceramics,
depending on the particle size in the raw material. The definition
according to Hausner applies to the structure of the fired
ceramic, specifically to the grain structure. The boundary
is considered to lie at grain sizes of between about 0.1 and
0.2 mm. If the elements of the microstructure are smaller
than 0.1 mm, which means that they can no longer be detected
with the naked eye, the German usage then refers to fine ceramics
– regardless of the material.
Technical ceramics, tableware,
decorative ceramics, ceramic sanitary ware, wall and floor
tiles and ceramic abrasives belong to the fine ceramics category.
The category of coarse ceramics includes,
for example, brick or conventional refractory materials.
Technical ceramics refers
to ceramic products for engineering applications.
Terms commonly seen in literature such as:
- high performance ceramics
- structural ceramics
- construction ceramics
- industrial ceramics
- engineering ceramics
- functional ceramics
- electrical ceramics
- cutting ceramics and
- medical ceramics
describe special aspects of technical ceramics.
A categorisation along these lines is not very useful, since
in some cases they overlap significantly.
is defined in DIN V ENV 12 212 as a "highly-developed,
high-strength ceramic material, which is primarily non-metallic
and inorganic and possesses specific functional attributes."
The concept high-performance ceramics
is primarily used to distinguish them from traditional ceramics
based on clay, including tableware, sanitary ware, walls and
floor tiles as well as ceramics for civil engineering. This
definition agrees with that of the "Japanese Fine Ceramics
Structural or construction
ceramics are terms that have not yet been standardised,
referring to materials that in some way must withstand mechanical
stresses, bending or pressure for example. The concepts industrial
and engineering ceramics have practically
Functional ceramics are
high-performance ceramics in which the inherent characteristics
of the material play an active role, for example ceramic parts
which possess specific electric, magnetic, dielectric or optical
Electrical ceramics are
high-performance ceramics that are applied because of their
specific electric or electronic characteristics. Electrical
engineering applications make use primarily of the excellent
insulating characteristics and mechanical strength. The electronics
industry also takes advantage of characteristics such as ferroelectric
behaviour, semiconductivity, non-linear resistance, ionic
conduction, and superconductivity.
Cutting tool ceramics are
high-performance ceramics that are applied in machining processes
(lathe bits, drilling, milling) due to their excellent wear
and high-temperature resistance.
Medical ceramics are high-performance
ceramics for medical applications, in other words within the
human body, and are represented by products that repair or
replace bone, teeth or other hard tissues.
Further definitions are contained in DIN
EN 12 212.