Dear Akash Kumar Sahu

ε stands for the material permittivity and it is used to evaluate the Q factor (1/Q) of the material. The Q factor itself is the ratio of the material initial energy stored/energy lost in one radion of cycle of oscillation that can be from mechanical, electrical, and other possibilities. It is considered to be the dissipation factor (DF) of the material.

The permittivity can have real (ε') and imaginary components (ε'').

Said that, according to Maxwell's curl equation for time-varying electromagnetic fields, the ε′′ is the imaginary component of permittivity attributed to bound charge and dipole relaxation and the free charge conduction is quantified by σ.

So tan(δ) stands for the ratio between the lossy reaction to the electric field (ε''+σ) in the curl equation to the lossless reaction (ε'),

the ELECTRIC loss tangent can be evaluated by tan(δ): ε''/ε', i.e, the ratio between the lossy and lossless reaction to the Electric field.

To my point of view, when the authors are evaluating ε'' vs frequency they are looking at how the oscillation can affect the lossy reaction to the electric field. It does not say anything alone because we need to know the lossless part in order to quantify much electromagnetic energy was dissipated by the oscillation.

But, when they are evaluating tan δ vs frequency they are evaluating how the oscillation can affect both ε' and ε'' and directly the Dielectric Loss, i.e, the electromagnetic dissipation energy.

And yeah, we need to consider that each kind of material have a specific behaviour due to their complex-valued permittivity ε, and it can be defined according to what you saw through ε''/ε. I hope that you can get the path from here

Regards,

Akash Kumar Sahu

You can read this paper:

Article Comparative study on dielectric and structural properties of...

Akash Kumar Sahu

You can read this paper:

Article Comparative study on dielectric and structural properties of...

Thank you, Matheus Mendes for your response. Appreciate it.

dissipation factor and tan delta are same.

Dielectric loss is equal to the product of (epsilon prime and tan delta).

Kindly refer to standard books which are widely available.

Dielectric loss/loss tangent (tan δ) is the attenuation of a signal as it propagates. This attenuation is the result of EM wave absorption in the dielectric materials.

tan δ is also referred to as dissipation factor (εʺ) by many researchers.

A very common equation relates these two quantities,i.e., ε" = ε' * tan δ. This can be found in any of the standard textbooks discussing dielectric materials.

Hope this helps you.

εʺ shows how the oscillations can effect the lossy reaction to electric field whereas tan δ depicts how the oscillations effect both ε' and ε'' i.e. the electromagnetic dissipation energy.