Materials

3 Ceramic Materials

3.1 Definitions

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 business statistics.

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:

describe special aspects of technical ceramics. A categorisation along these lines is not very useful, since in some cases they overlap significantly.

High-performance ceramic 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 Association".

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 identical meanings.

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 properties.

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.