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Structure and physical property relations of Mn ilvaite - Part II: Electrical conductivity and thermopower

Schmidbauer, E., T. Fehr, R. Hochleitner, and J. Schneider (2005), Structure and physical property relations of Mn ilvaite - Part II: Electrical conductivity and thermopower, Physics and Chemistry of Minerals, 32(5-6), 400-411.

Abstract
DC and AC electrical conductivities were measured on a monocrystalline Mn-rich ilvaite sample in the temperature range similar to 130 K < T < similar to 300 K. Impedance spectroscopy was applied to determine the DC conductivity sigma(DC), extrapolating AC data to zero frequency. The conductivity sigma(DC), measured parallel (parallel to) and perpendicular (perpendicular to) to the [001] direction, exhibits semiconducting behaviour with a non linear log sigma(DC) - 1/T relationship. A distinct anisotropy was found with sigma(DC)( 300 K) similar to 4 x 10(-2) Omega(-1) cm(-1) parallel to [ 001] and similar to 1 x 10(-4) Omega(-1) cm(-1) perpendicular to [001]. The AC conductivity sigma'(omega) (omega/2 pi = frequency) is enhanced in both directions relative to sigma(DC) at low temperatures, with a marked effect for high frequencies within the range 20 Hz - 1 MHz. For the frequency dependence parallel to [001], an approximate power law is valid sigma'(omega) proportional to omega(s), with s< 1. This behaviour is typical for hopping charge transport between localized states. Charge transfer is suggested to occur by electron hopping between mixed-valence Fe cations according to Fe2+ --> Fe3+ preferentially along chains parallel to [001]. The absolute thermopower Theta ( Seebeck- effect) parallel to [ 001] has a positive sign and it is Theta proportional to 1/ T, while Theta perpendicular to [001] is negative and shows hardly a temperature variation within the range similar to 300 K and similar to 430 K. The results are discussed in terms of one-dimensional models of electron hopping between localized states.
BibTeX
@article{id141,
  author = {E. Schmidbauer and T. Fehr and R. Hochleitner and J. Schneider},
  journal = {Physics and Chemistry of Minerals},
  number = {5-6},
  pages = {400-411},
  title = {{Structure and physical property relations of Mn ilvaite - Part II: Electrical conductivity and thermopower}},
  volume = {32},
  year = {2005},
  language = {en},
}
EndNote
%0 Journal Article
%A Schmidbauer, E.
%A Fehr, T.
%A Hochleitner, R.
%A Schneider, J.
%D 2005
%N 5-6
%V 32
%J Physics and Chemistry of Minerals
%P 400-411
%T Structure and physical property relations of Mn ilvaite - Part II: Electrical conductivity and thermopower
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Printed 06. Dec 2019 02:22