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Physics and Chemistry of Minerals

, Volume 32, Issue 5–6, pp 400–411 | Cite as

Structure and physical property relations of Mn ilvaite

Part II: Electrical conductivity and thermopower
  • E. SchmidbauerEmail author
  • Th. Fehr
  • R. Hochleitner
  • J. Schneider
Original Paper
  • 67 Downloads

Abstract

DC and AC electrical conductivities were measured on a monocrystalline Mn-rich ilvaite sample in the temperature range ∼130 K < T < ∼300 K. Impedance spectroscopy was applied to determine the DC conductivity σDC, extrapolating AC data to zero frequency. The conductivity σDC, measured parallel (∥) and perpendicular (⊥) to the [001] direction, exhibits semiconducting behaviour with a non linear log σDC−1/T relationship. A distinct anisotropy was found with σDC(300 K) ∼4×10−2 Ω−1 cm−1 ∥ [001] and ∼1×10−4 Ω−1 cm−1 ⊥ [001]. The AC conductivity σ′(ω) (ω/2 π = frequency) is enhanced in both directions relative to σDC at low temperatures, with a marked effect for high frequencies within the range 20 Hz–1 MHz. For the frequency dependence ∥ [001], an approximate power law is valid σ′(ω) ∝ ω 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 ∥ [001]. The absolute thermopower Θ (Seebeck-effect) ∥ [001] has a positive sign and it is Θ ∝ 1/T, while Θ ⊥ [001] is negative and shows hardly a temperature variation within the range ∼300 K and ∼430 K. The results are discussed in terms of one-dimensional models of electron hopping between localized states.

Keywords

Electrical conductivity Thermopower Mn-rich ilvaite 

Notes

Acknowledgements

One of the authors (E.S.) is indebted to the Deutsche Forschungsgemeinschaft for financial help.

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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • E. Schmidbauer
    • 1
    Email author
  • Th. Fehr
    • 2
  • R. Hochleitner
    • 3
  • J. Schneider
    • 4
  1. 1.Department für Geo- und Umweltwissenschaften, Sektion GeophysikUniversität MünchenMünchenGermany
  2. 2.Department für Geo- und Umweltwissenschaften, Sektion Mineralogie, Petrologie und GeochemieUniversität MünchenMünchenGermany
  3. 3.Mineralogische StaatssammlungMünchenGermany
  4. 4.Department für Geo- und Umweltwissenschaften, Sektion Kristallographie und Angew. MineralogieUniversität MünchenMünchenGermany

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