Advanced ceramics offer superior dielectric properties compared to those of metals and plastics. Advanced ceramics are insulating materials: they do not conduct electrical currents. This physical property is called resistivity. Other electrical properties, such as dielectric strength, relative permittivity (or dielectric constant) and the loss angle, vary from one ceramic to the next.
Description
Resistivity is the ability of a material to oppose the flow of electric current. The SI unit of electrical resistivity is the ohm-metre and corresponds to the resistance measurement of a test piece of a given cross-section and length. High-purity alumina advanced ceramics (≥94 %) have the highest resistivity values (>1.10 14), followed by aluminium nitride (> 1.10 12), sintered silicon nitride (>1.10 10) and zirconia (> 1.10 9). Silicon carbide is the least insulating ceramic with resistivity of around 1.10 6, or even less for certain forms of CVD-SiC. Quartz and Macor glass-ceramics are better insulators, with resistivity values of over 1.10 16.
Application markets
The business areas where these materials are used are varied: electronics, defence, medical instrumentation, energy, transport, aeronautical and spatial, etc.
Comparative table of properties
| Values at ambient temperature – 20°c |
Resistivity (Ω.m) |
Dielectric strength (KV/mm) | Dielectric loss factor (tan ɗ) |
Dielectric constant (K’) |
|
Alumina (94 to 99.8 % ) |
>1012 to 1015 | 17 to 40 |
1,5.10-4 to 3.10-5 |
9.5 to 11 |
| Aluminium nitride |
5.1012 to 1013 |
16 to 20 | 0,5.10-3 | |
| Sintered silicon nitride |
> 1010 to 1011 |
15 | - | - |
| Quartz |
1016 to 1018 |
25 to 40 | 10-3 to 10-4 | 3.7 |
These values are for information only and do not constitute a contractual obligation.