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
The relative permittivity of a material is its absolute permittivity expressed as a ratio relative to the permittivity of a vacuum. This property is also known as the dielectric constant, expressed by the symbol K, and is the factor by which the electric field between the charges (capacitor) is decreased. The more insulating the material, the lower the dielectric loss, expressed by the loss tangent tan ɗ, that could result from the application of a magnetic field.
In applications that require low permittivity and dielectric loss, high-purity (≥97 %) alumina advanced ceramics offer the highest dielectric constant values and lowest tan ɗ values, followed by aluminium nitride and Macor glass ceramics. Quartz has a low dielectric loss but a rather low dielectric (low-k) constant. Zirconia, silicon carbides and silicon nitrides are not suitable for this type of application.
Application markets
These materials are most commonly used in the field of power electronics, possibly combined with a vacuum environment and microwave electronics.
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.