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Study of the electrical charge transport in ilvaite using impedance spectroscopy and thermopower data

Schmidbauer, E., and G. Amthauer (1998), Study of the electrical charge transport in ilvaite using impedance spectroscopy and thermopower data, Physics and Chemistry of Minerals, 25(7), 522-533.

Abstract
The electrical conduction in the mineral ilvaite was studied between approximate to 170 and 450 K. A natural ilvaite from Elba (Italy) was found to be semiconducting with a DC conductivity 1.8x10(-3) (Omega cm)(-1) at 300 K, measured parallel(parallel to) to the [001] direction; perpendicular (perpendicular to) to [001] it was 1.4x10(-5) (Omega cm)(-1), i.e. the conductivity is highly anisotropic. The conduction is effected by a hopping charge transport between localized levels in the energy gap associated with activation energies E-A=0.3-0.5 eV. It is concluded that impurities (Mg,Al,Mn) may play a decisive role in the charge hopping transport parallel to [001] that is basically governed by Fe2+-Fe3+ pairs on A-sites of the lattice as the source of electrons. Although the E-A-values were similar for both measured directions, the sign of thermopower is different which points to different charge transfer mechanisms. The bulk DC conductivity sigma(DC)(AC) for measurements parallel to [001], obtained by extrapolation of AC data using impedance spectroscopy, could only be determined at T<300 K owing to sample-electrode interfacial effects. In contrast, the bulk sigma(DC)(AC) perpendicular to [001] showed a slight break at approximate to 380 K that may reflect the structural phase transition monoclinic-->orthorhombic at approximate to 345 K. From AC conductivity measurements in the frequency range 20 Hz-1 MHz at T<300 K, a dispersive character of electronic relaxation was found, resembling that of amorphous semiconductors and of impurity conduction in crystalline semiconductors where it was ascribed to charge hopping processes of electrons between localized levels of cation pairs or clusters of limited lengths.
BibTeX
@article{id218,
  author = {E. Schmidbauer and G. Amthauer},
  journal = {Physics and Chemistry of Minerals},
  number = {7},
  pages = {522-533},
  title = {{Study of the electrical charge transport in ilvaite using impedance spectroscopy and thermopower data}},
  volume = {25},
  year = {1998},
  language = {en},
}
EndNote
%0 Journal Article
%A Schmidbauer, E.
%A Amthauer, G.
%D 1998
%N 7
%V 25
%J Physics and Chemistry of Minerals
%P 522-533
%T Study of the electrical charge transport in ilvaite using impedance spectroscopy and thermopower data
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Printed 17. Aug 2019 22:57