Isolating ceramics and glasses for electrotechnics and electronics

The notion of electrical insulation naturally refers to the function of separating conductors or components in electrical or electronic circuits that are at different electrical potentials, whether in the very high voltage range or, conversely, at very low voltages. Materials that perform this function prevent the passage of an electric current. They are called "insulators". They can be made, for example, of gases, paper, oils or minerals such as micas. Many of these are porcelains, oxides or nitrides produced by ceramic technology, or glass.

In this insulating application, the material has no other function than to electrically insulate objects, conductive or not, brought to different electrical potentials. It may also be desirable to exploit the dielectric properties associated with the insulating properties, for example in the manufacture of capacitors, or to ensure interconnection between various components brought together in an electronic device working at very high frequency.

This notion of electrical insulation can also be considered much more broadly, by including applications where materials can be insulators or conductors depending on the temperature or electrical voltage gradient applied to them.

Last but not least, we'll be talking about materials whose desired property is, for example, magnetic or piezoelectric, but which cannot be exploited without also being insulating.

A brief reminder at the beginning of the document explains the fundamental differences between glass and ceramics:

• glasses are materials that can be described as liquids, whose very high viscosity at room temperature means they can be likened to amorphous solids;

• Ceramics are materials with a crystalline structure, characterized by a microstructure of grains and grain boundaries.

The various mechanisms of electrical conduction in the volume and on the surface of crystalline materials such as ceramics and amorphous materials such as glasses are then described. Finally, compositions that enable ceramics and glasses to qualify as "insulating materials" are briefly presented.