Dear Dr. Khripov:
Matching High permittivity with low dielectric loss
Both questions should be approached with significant careful. See, there are no rule and several exceptions.
If a homogeneous and single phase ceramic is the prototype material of this analysis, we should have grain and grain boundary regions, in which bulk or grain really interest.
The concept of High permittivity and low dielectric loss match when specific defects are further engineered in crystallographic way. In this sense, such defects are represented as sub-levels in gap.
The parameter dielectric loss is ascribed to electrical conduction; in fact a low level electric current is operational, with direct effect under aging of material.
The defect associated to development of high permittivity; in a broad sense are intrinsic and extrinsic defects that are not involved with long range moving carrier, electrons, but with charge density and electron-lattice kind coupling. Here, typically a new set of defect with distinct level in gap are formed.
On the possibility
Both phenomena are ascribed to distinct type of defect and its eventual interaction with crystalline lattice. In a gross manner, crystalline structure with more low symmetry, complex structures with great set of distinct crystallographic sites, ferroelectrics and materials that exhibits combinations of these characteristics is further candidate.
On the necessary physics
Materials Physics combined with Physical of Dielectrics and further characterization techniques, as Impedance spectroscopy or Dielectric spectroscopy.
In addition, as comment, major part of condition to attain the perfect response of material should involve advanced techniques of ceramic processing.
with best regards
Marcos Nobre
Dear Dr. Khripov:
Matching High permittivity with low dielectric loss
Both questions should be approached with significant careful. See, there are no rule and several exceptions.
If a homogeneous and single phase ceramic is the prototype material of this analysis, we should have grain and grain boundary regions, in which bulk or grain really interest.
The concept of High permittivity and low dielectric loss match when specific defects are further engineered in crystallographic way. In this sense, such defects are represented as sub-levels in gap.
The parameter dielectric loss is ascribed to electrical conduction; in fact a low level electric current is operational, with direct effect under aging of material.
The defect associated to development of high permittivity; in a broad sense are intrinsic and extrinsic defects that are not involved with long range moving carrier, electrons, but with charge density and electron-lattice kind coupling. Here, typically a new set of defect with distinct level in gap are formed.
On the possibility
Both phenomena are ascribed to distinct type of defect and its eventual interaction with crystalline lattice. In a gross manner, crystalline structure with more low symmetry, complex structures with great set of distinct crystallographic sites, ferroelectrics and materials that exhibits combinations of these characteristics is further candidate.
On the necessary physics
Materials Physics combined with Physical of Dielectrics and further characterization techniques, as Impedance spectroscopy or Dielectric spectroscopy.
In addition, as comment, major part of condition to attain the perfect response of material should involve advanced techniques of ceramic processing.
with best regards
Marcos Nobre
The Kramers–Kronig relations are mathematical formulae, connecting the real and imaginary parts of a complex function that is analytic. In particular these relations are used to find the relationship between the real and the imaginary part of permittivity. If permittivity of a dielectric can be described by simply Debye model then maximum dielectric losses appear at the frequency of the maximum slope (derivative) of the real part of permittivity. Good example of such behavior is permittivity of water. Generally one can expect that nondispersive dielectric would exhibit lower losses (especially at the frequency ranges where dispersion is negligible). For low loss materials e.g. polymers such statement might not be entirely correct. Some nondispersive plastics may exhibit two orders of magnitude larger losses than the other. E.g. plexiglass versus Teflon.
Also some very high permittivity materials like rutile or KTO exhibit very low dielectric losses.
Dear KhriPov,
Most of the fact well mentioned by Dr. Norbe and Dr. Krupka, I would only like to add in short:
When you say dielectric loss that means tan delta (= e"/e') for dielectric / non conducting materials. However due to presence of defect. there some resistive path exist through which capacitive stored energy lost through conduction(s). So in the (almost) defect free dielectric materials (e" + s) will be small and high e' mean low tan delta.This is how it matches for Ferroelctrics(FE)/Piezoelectrics.
However for polycrystalline (ferro) magnetic samples where domain wall thickness is too large as compare to FE, so more loss is possible, here it could not match (most of time).
The permittivity at low frequency is a consequence of all absorptions at higher frequencies (as mentioned by Jerzy Antoni Krupka , due to the Kramers-Kronig Relations). So you have to choose a material with strong absorption at a (sometimes much if the oscillator is strongly damped) higher frequency than the one you are interested in...
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