Technical Ceramics - Materials with Compelling Benefits

Ceramic materials have found a permanent place in engineering, and their ongoing evolution keeps opening up new technical application opportunities. Engineering solutions based on ceramic materials are usually compelling because they rely on special properties and property combinations which no other material have to offer.

Technical ceramics have long become a ubiquitous feature in our lives. Many household appliances would not be able to function without ceramic insulating elements. Insulators, fuses and circuit-breaker components made of technical ceramics are essential to a safe and reliable power supply. Ceramic substrates and components form the basis for a broad range of devices and subassemblies in all fields of electronics, while ceramic sealings and regulator discs ensure a wear-free operation and proper sealing in many valves and household water taps. These few examples may suffice to illustrate the important role played by technical ceramics in the world today. On the other hand, ceramic components are usually not highly visible, being designed as parts of larger functional units in plant and equipment, machinery and motor vehicles. As a result, we have come to rely on technical ceramics in everyday life but are rarely ever aware of their presence.

Traditional ceramic materials

In 1849, when Werner von Siemens built the telegraph line from Frankfurt/Main to Berlin, he was already relying on porcelain insulators. As a material for fuses, switches, lamp sockets and many other components, porcelain became an important adjunct to the evolution of electrical engineering.

Porcelain, or quartz porcelain as it is more properly called, is made of very few all-natural raw materials: quartz, feldsparand kaolin. As the traditional material in silicate ceramics, it already possesses all the major characteristics of technical ceramics, e.g., insulating capabilities, dimensional stability, hardness, thermal resistance and resistance to corrosion.

Increasing demands on ceramic components for electric power generating and distribution systems and mechanical engineering uses have since led to improved material properties and the development of new manufacturing methods. The replacement of quartz with aluminum oxide yielded alumina porcelain, noted for its superior strength. A similar development took place in the field of soapstone materials, giving rise to the use of steatite and cordierite. Today, silicate ceramics enable highly cost-efficient and dependable solutions in electrical installations and fuse and circuit-breaker technology, as well as in a number of high-temperature applications.

The widespread use of technical ceramics in electrical engineering created a need for a definition and description of these materials and their characteristics. Electrical engineering standards emerged at a very early date. One widely known standard is VDE 0335, which later evolved into the international standard IEC 672.

Oxide ceramic materials

Synthetic feedstock, mainly oxides and mixed oxides, forms the basis for this group of ceramic materials. The most important oxide ceramic material is aluminum oxide (Al₂O₃). It combines all the essential properties of technical ceramics and meets the diverse requirements of key applications such as electronics, electrical engineering, instrumentation and control technology, and mechanical and process engineering.

Other oxide ceramics are noted for special properties such as high toughness, temperature resistance and thermal shock resistance, which open up unique application opportunities today while offering exciting perspectives for the future.

Ceramics generate movement

Piezoceramic materials are able to convert pressures into electrical pulses and vice versa. As sensors, generators and actuators, piezoceramic components have found their way into the most diverse applications. In automotive engineering they ensure the timely deployment of air bag systems, while in medical lithotripter systems they generate ultrasonic shock waves which shatter kidney stones and have become the key to non-invasive treatment.

Non-oxide ceramic materials

These high-performance materials are made of man-made non-oxidic powders. Among the carbides, nitrides, borides and silicides which are of significance in this context, silicon carbide (SiC) and silicon nitride (Si₃N₄) are the most commonly used materials. Silicon carbide is excellently suited for components required to withstand high mechanical and corrosive loads in addition to temperatures more than 1400°C. Typical examples are found in machinery and process engineering. Other non-oxide ceramics combine a low specific weight with high toughness. Combustion engines with silicon nitride valves have been successfully tested in vehicle road trials. Aluminum nitride, with its high thermal conductivity, ensures efficient cooling for power semiconductors.

Manufacturing expertise in technical ceramics

In order to benefit fully from the advantages of these materials, a prudent integration of the ceramic component into the overall system will generally be necessary. Advice from an experienced manufacturer can be of valuable assistance in this process. Materials and application engineers will be glad to help with the analysis and definition of requirement criteria and design specifications, starting at the component development stage. Application conditions influence the material selection and product shape as well as the pre-assembly conditioning steps. Manufacturers generally aim to achieve the final product shape at the end of the firing ("sintering") process. Thus, over 80% of all components produced today leave the production line in a ready-to-install state and require no further treatment.

The future belongs to system solutions

The potential of ceramic materials are far from exhausted, since their diverse properties form a sound basis for further innovative approaches. A design which takes into account the specific capabilities and requirements of ceramics and ensures their proper integration into the specific environment will usually give rise to products which are more functional, reliable and durable than traditional solutions.

September 1996
Reprint permitted free of charge.

03. July 2003