Dielectric material becomes conductive at High Frequency?

logic5

Dear colleagues,


I have a question related with dielectrics and their conductivity when High Frequency signals are applied.


Is it possible to become conductive a dielectric material if sufficiently High Frequency signals are applied?


When a high frequency signal is applied to a dielectric, at certain frequencies material's dielectric constant falls (this behaviour can be observed in a dielectric spectroscopy). This behaviour is due to the ionic and dipole relaxation and atomic and electronic polarization.

I have heard, at these points, when the dielectric constant falls (or dielectric losses increases) the dielectric material becomes slightly conductive.


Is this true? Could you correct me if not or give me more information about it?


Thank u in adavance,

logic

Mentz114

Welcome to the Forum.

It depends what you mean by conductive. DC conductance requires certain energy bands being available to electrons in the material. But as you know you can 'conduct' AC through a capcitor which is not DC conducting.

If the dielectric material experienced some significant change in its electronic configuration, I suppose it would be possible for it to become a DC conductor.

logic5

I mean if it becomes conductive at AC.
Simplifying, the question would be... is is possible to apply a low frequency signal to a dielectric material and not to be conductive, but when increasing the frequency to become conductive?

Mentz114

I'm not qualified to go further with this - maybe someone else knows ?

lpfr

Yes! I saw it by myself on the material (kind of formica) over the benches in an electronic lab. The working frequency was about 470 MHz. When "hot" parts of the circuit touched the formica, you could see the change in frequency response.
P.S. The circuit was a single transistor amplifier and the "hot" part was the transistor case. I was the teacher.

logic5

Thank you for your feedbacks!