Two definitions of material dissipation factor

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The discussion centers on the definitions of the material dissipation factor (Df) and dielectric constant (Dk). The first definition describes Dk as the relative permittivity and Df as the ratio of energy lost to energy stored. The second definition, referenced from a webinar, inaccurately equates the imaginary component of complex permittivity with Df. The consensus is that the first definition is correct, while the second is considered a poor formulation. Clarity in these definitions is essential for accurate understanding in materials science.
senmeis
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material dissipation factor
Hi,

I have seen two versions of definitions of material dissipation factor Df:

The first one:
Dk (dielectric constant) = K = relative permittivity = ɛ -jɛ’ , ɛ = energy stored and ɛ’ = energy lost.
Df (dissipation factor/loss tangent) = ratio of ɛ’ and ɛ

The second one:
On slide 8 of webinar http://www.globalcommhost.com/roger...17_JC_microstrip_coplanar_stripline_final.pdf:
The imaginary component of complex permittivity is Df (dissipation factor).

Which one is correct?
 
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The first definition is correct. Regarding the second one, I think it's just a sloppy formulation.
 
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