IMMITTANCE%20SPECTROSCOPY%20Models,%20data%20fitting,%20and%20analysis

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IMMITTANCE SPECTROSCOPYModels, data fitting, and
analysis

• J. Ross Macdonald
• IMSPEMAS Workshop
• Warsaw 9/2003

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MATERIAL/ELECTRODE CHARACTERIZATION WITH IS

• Bulk resistivity and dispersion
• Bulk dielectric constant
• Mobile charge concentrations
• Mobilities and valence numbers
• Bulk dissociation and recombination rates
• Electrode reaction rate constant
• Electrode adsorption rate constant
• Other fit-model parameters

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IMMITTANCE SPECTROSCOPY

• Impedance Spectroscopy
• Dielectric Spectroscopy
• Data Analysis
• CNLS INVERSION
• LEVM ---- LEVMW V. 8

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CNLS-LEVM-LEVMW

• CNLS Complex nonlinear least squares fitting.
• Fit complex data to a model whose parts
  satisfy the Kronig-Kramers transform relations
• LEVMW Windows version of LEVM, a free general
  CNLS fitting and inversion program. Download it
  and its manual from http//www.physics.unc.edu/ma
  cd/
• LEVMW can accurately fit data to K0, K1, and many
  other models. It allows temporal response to be
  calculated from frequency response and vice versa

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ELECTRODE EFFECTS AND SLOPES
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BULK K0 AND K1 FIT RESULTS
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NEARLY CONSTANT LOSS
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CONCLUSIONS

• The Moynihan original modulus formalism
  dispersion model is theoretically and
  experimentally incorrect and should be replaced
  by the corrected modulus formalism.
• The corrected modulus formalism is isomorphic to
  the Scher-Lax microscopic model and leads to
  virtually independent of temperature and ionic
  concentration.

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• The variable-correlation assumption of the OMF
  and NCM is unsupported by fits of experimental
  data using the CK1 CMF model.
• The cutoff model is much superior to all coupling
  models and requires no ad hoc assumptions.
• Nearly-constant-loss behavior is likely to be
  associated with coupling between vibrating ions
  and induced dipoles of the bulk material. A
  microscopic model of the process is needed.

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MATERIAL CHARACTERIZATION

• Conduction character
• Intrinsically conducting
• a. Completely blocking electrodes
• b. Partially blocking electrodes
• Intrinsically insulating
• a. Dielectric no mobile charge
• b. Leaky dielectric surface or bulk impurity
  conduction
• Charge characteristics
• Supported strong supporting electrolyte, as
  in liquids
• Unsupported no supporting electrolyte, as in
  glasses, solid electrolytes, semiconductors

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