The paper reports potassium diffusion measurements performed on gem-quality single-crystal alkali feldspar in the temperature range from 1169 to 1021\mboxK. Natural sanidine from Volkesfeld, Germany was implanted with \mbox43\mboxK at the ISOLDE/CERN radioactive ion-beam facility normal to the (001) crystallographic plane. Diffusion coefficients are well described by the Arrhenius equation with an activation energy of 2.4\mboxeV and a pre-exponential factor of 5×10−6\mboxm2/\mboxs, which is more than three orders of magnitude lower than the \mbox22\mboxNa diffusivity in the same feldspar and the same crystallographic direction. State-of-the-art considerations including ionic conductivity data on the same crystal and Monte Carlo simulations of diffusion in random binary alloy structures point to a correlated motion of K and Na through the interstitialcy mechanism.
@article{arxiv.1701.02884,
title = {Potassium self-diffusion in a K-rich single-crystal alkali feldspar},
author = {Fabian Hergemöller and Matthias Wegner and Manfred Deicher and Herbert Wolf and Florian Brenner and Herbert Hutter and Rainer Abart and Nicolaas A. Stolwijk},
journal= {arXiv preprint arXiv:1701.02884},
year = {2017}
}