Ionic conductivity in gem‑quality single‑crystal alkali feldspar from the Eifel: temperature, orientation and composition dependence

Author(s)

Hamid El Maanaoui, F. Wilangowski, A. Maheshwari, Hans-Dieter Wiemhöfer, Rainer Abart, Nicolaas A. Stolwijk

Abstract

We measured the ion conductivity of single-crystal alkali feldspar originating from two different locations in the Eifel/Germany, named Volkesfeld and Rockeskyller sanidine and having potassium site fractions

_CK of 0.83 and 0.71, respectively. The dc conductivities resulting from electrochemical impedance spectroscopy over the temperature range of 300–900

^∘C show a weak composition dependence but pronounced differences between the b-direction [⊥ (010)] and c

^∗-direction [⊥ (001)] of the monoclinic feldspar structure. Conductivity activation energies obtained from the observed linear Arrhenius plots are close to 1.2 eV in all cases, which is closely similar to the activation energies of the

²²Na tracer diffusivity in the same crystals. Taking into account literature data on K tracer diffusion and diffusion correlation effects, the present results point to a predominance of the interstitialcy mechanism over the vacancy mechanism in mass and charge transport on the alkali sublattice in potassium-rich alkali feldspar.

Organisation(s)

Department of Lithospheric Research

External organisation(s)

Universität Münster

Journal

Physics and Chemistry of Minerals

Volume

43

Pages

327–340

No. of pages

14

ISSN

0342-1791

DOI

https://doi.org/10.1007/s00269-015-0797-y

Publication date

01-2016

Peer reviewed

Yes

Austrian Fields of Science 2012

105116 Mineralogy, 105120 Petrology

Keywords

ASJC Scopus subject areas

Geochemistry and Petrology, Materials Science(all)

Portal url

https://ucrisportal.univie.ac.at/en/publications/ionic-conductivity-in-gemquality-singlecrystal-alkali-feldspar-from-the-eifel-temperature-orientation-and-composition-dependence(49ee882c-e988-4fc6-a18c-f6cc499f2cc5).html