Oxide ceramics

Various raw materials from mining areas in the whole world form the basis for the production of high-quality oxides and mixed oxides. Following materials belong to the group of the oxide ceramics materials:

• aluminium oxide
• magnesium oxide
• zirconium oxide
• aluminium titanate
• piezo ceramic

Alumina with its Al2O3 content of more 80% to more than 99% is technically the most important oxide ceramic material. It is characterised by

• a high strength and hardness,
• high resistance to wear and corrosion,
• high thermal conductivity,
• excellent insulation properties,
• high toughness and
• high-temperature strength.

Application: This material is more or less employed in all field of application because of its many properties and combination of properties and because of its good price-performance ratio.

• electrical engineering,
• in electronics,
• in mechanical and plant engineering,
• in chemical and processing technology,
• in medical technology and
• in high temperature engineering.

This material is mostly produced as high-grade, so called unary ceramic, in porous or gas-tight form. Special characteristics are

• the good electrical insulation properties and
• its thermal conductivity.

Magnesium oxide is used

• in heat engineering for the production of tubes with specifically defined strength, as well as
• in insulation material e.g. casings.

Zirconia occurs in monoclinic, tetragonal and cubic crystal modifications and is produced as fully stabilised (FSZ), partially stabilised (TSZ) or tetragonal zirconia, depending on the dotage amount.

Zirconias have acquired a new significance in the last years due to their excellent tribiological properties,

• their high flexural and tensile strength,
• their high fracture toughness,
• their very good corrosion and wear resistance,
• their low thermal conductivity,
• their oxygen ion conductivity and
• their E-module like steel

Due to these properties zirconia ceramics are preferred for

• application in mechanically high-load components.

The oxygen ion conductivity is used for reading oxygen partial pressures e.g.

• in the Lambda probe in catalysts.

A stoichiometric composed phase of alumina and titania. The material convinces trough

• its low thermal expansion coefficient,
• combined with a very high resistance to thermal shock,
• low wettability trough aluminium and
• non-ferrous melting and open porosity.

Aluminium titanate is used for example as

• cylinder linings in motors,
• dampers and in foundries.

Today the most important piezoelectrical ceramic materials are based on the oxide mixed crystals system lead zirconate and lead titanate. The properties depend on the molar proportions (lead zirconate to lead titanate), as well as substitutions and dotage through additional elements. Piezo ceramics are able to set an electrical charge free during mechanical distortion or lead, due to the direct piezo-electrical effect.

If an inverse piezoelectrical effect takes place, then there is a change of dimension through an electrical field. Items there are possibilities for materials with very different specifications, for example

• sensors,
• high performance ultra sonic generators and
• actuators