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DIELECTRIC PROPERTIES OF ION -CONDUCTING MATERIALS

DIELECTRIC PROPERTIES OF ION -CONDUCTING MATERIALS. F. Kremer Coauthors: J. Rume, A. Serghei, . The relationship between the complex dielectric function e * and the complex conductivity s * Phenomenology of the conductivity of charge – conducting materials

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DIELECTRIC PROPERTIES OF ION -CONDUCTING MATERIALS

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  1. DIELECTRIC PROPERTIES OF ION -CONDUCTING MATERIALS F. Kremer Coauthors: J. Rume, A. Serghei,

  2. The relationship between the complex dielectric function e* and the complex conductivity s* Phenomenology of the conductivity of charge – conducting materials The dielectric properties of zwitterionic polymethacrylate The dielectric properties of „Ionic Liquids“ Theoretical descriptions of the observed frequency and temperature dependemce of the complex conductivity

  3. The spectral range of Broadband Dielectric Spectroscopy (BDS) and its information content for studying dielectric relaxations and charge transport.

  4. The linear interaction of electromagnetic fields with matter is described by Maxwell‘s equations (Ohm‘s law) Current-density and the time derivative of D are equivalent

  5. Dielectric spectroscopy electric field E Debye relaxation polarization P complex dielectric function

  6. Analysis of the dielectric spectra

  7. The spectral range (10-3 Hz to 1011 Hz) of Broadband Dielectric Spectroscopy (BDS) (sample amount required < 5 mg)

  8. Brief summary concerning Broadband Dielectric Spectroscopy (BDS) 1. The spectral range of BDS ranges from 10-3 Hz to 1011 Hz. 2. Orientational polarisation of polar moieties and charge transport are equivalent and observed both. 3. The main information content of dielectric spectra comprises for fluctuations of polar moieties the relaxation- rate, the type of itsthermal activation, the relaxational strength and the relaxation-time distribution function. For charge transport the mean attempt rate to overcome the largest barrier determining the d.c.conductivity and its type of thermal activation can be deduced

  9. Phenomenologyof the conductivity of charge – conducting materials

  10. Frequency and temperature dependence of the conductivity of a mixed alkali-glass 50LiF-30KF-20Al(PO3)3

  11. Frequency and temperature dependence of the conductivity of a zwitterionic polymer

  12. Frequency and temperature dependence of the electronic conductivity of poly(methyl-thiophene)

  13. Frequency and concentration dependence of the electronic conductivity of composites of carbonblack and poly(ethylene terephthalate)

  14. Mixed alkali-glass: Scaling with temperature is possible

  15. poly(methyl-thiophene): Scaling with temperature is possible

  16. composites of carbonblack and poly(ethylene terephthalate): Scaling withconcentrationis possible

  17. The Barton-Nakajima-Namikawa (BNN) – relationship holds for all materials examined:

  18. Experimental findings In all examined materials the conductivity shows a similar frequency and temperature (resp. concentration) dependence There is no principle difference between electron – and ion – conducting materials The conductivity „scales“ with the number of effective charge-carriers as determined by temperature or concentration A characteristic frequency exists where the frequency dependence of the conductivity sets in With increasing number of effective charge-carriers the conductivity increases. The BNN-relationship is fulfilled

  19. The dielectric properties of zwitterionic poly-methacrylate: poly{3-[N-[-oxyalkyl)-N,N-dimethylammonio]propanesulfonate}

  20. Dielectric data as displayed for the complex dielectric function e*(w,T)

  21. Dielectric data as displayed for the complex conductivity s*(w,T)

  22. Dielectric data as displayed for the complex electrical modulus M*(w,T) =1/ e*(w,T)

  23. Dyre‘s random free energy barrier model Hopping Conduction in a spatially randomly varying energy barrier :

  24. Fits using the Dyre theory „work well“

  25. The rates wc, wM and 1/te nearly coincide and have - over 5 decades - a similar temperature dependence

  26. The BNN-relationship holds for varying the charge carrier concentration

  27. Summary The dielectric properties of the zwitterionic poly-methacrylate: poly{3-[N-[-oxyalkyl)-N,N-dimethylammonio]propane sulfonate} are characterized by a pronounced frequency - and temperature dependence. It should be analysed in terms of the complex dielectric function e*(w,T), the complex conductivity s*(w,T) and the complex electrical modulus M*(w,T) =1/ e*(w,T) The data can be well described by Dyre‘s random free energy barrier model The BNN-relation is fulfilled At low frequencies electrode polarisation effects show up

  28. The dielectric properties of „Ionic Liquids“ BMIM BF4BMIM SCN 1-butyl-3-methylimidazolium tetrafluoroborate 1-n-butyl-3-methylimidazolium thiocyanate

  29. Temperature dependence Imaginary and real part of the complex dielectric function are strongly temperature dependent

  30. Temperature dependence The complex conductivity of the ionic liquid BMIM BF4 is also strongly temperature dependent

  31. Broadband dielectric measurements displayedfor the complex dielectric function e*(w,T)

  32. Broadband dielectric measurements displayedfor the complex conductivity s*(w,T)

  33. Scaling with temperature possible

  34. Scaling with temperature as displayed in terms of the complex conductivity s*(w,T) All data collapse into a single characteristic curve

  35. Scaling with concentration for NaCl solutionsas displayed for the complex dielectric function Scaling possible but deviations on the low frequency side

  36. Scaling with concentration for NaCl solutionsas displayed for the complex conductivity ws is the angular frequency of the minimum in s´´

  37. Fits using the Dyre-model of conduction The Dyre –model describes the observed frequency- and temperature dependence; additionally electrode polarization effects show up

  38. Fits using the Dyre-model Electrode polarization effects show up already at 100 kHz

  39. The BNN Relation is fulfilled for s0 and te as obtained from Dyre-fits

  40. Alternative approach: Superposition of a thermally activated d.c. conductivity and „nearly constant loss“ contribution. :Near constant loss contribution The BNN relation is a trivial consequence

  41. Activation plots Boths0and1/te show a VFT - dependence

  42. Final Summary The dielectric properties of „Ionic Liquids“ are similar to other ion - conducting systems They should be analysed in terms of the complex dielectric function e*(w,T), the complex conductivity s*(w,T) and the complex electrical modulus M*(w,T)=1/ e*(w,T) The data can be well described by Dyre‘srandom free energy barrier model but as well a superposition a thermally activated d.c.conductivity,a power law and a „nearly constant loss“ contribution The BNN-relation is fulfilled At low frequencies electrode polarisation effects show up

  43. Thanks to Joshua Rume and A. A. Serghei and financial support through the DFG

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