Single‐Crystal Structure and Electronic Conductivity of Melt Synthesized Fe‐rich, near End‐Member Ferro‐Kinoshitalite. Issue 21 (30th October 2017) - Daab, Matthias
Abstract : In an attempt to improve the electronic conductivity an Fe II ‐rich brittle mica, a near end‐member Ferro‐Kinoshitalite (BaFe3 Si2 Al2 O10 F2 ) was synthesized via a melt approach. The structure is of 1M polytype [ a = 5.4013(11) Å, b = 9.3659(19) Å, c = 9.987(2) Å, β = 100.52(3)°, C 2/ m ] and the iron content clearly exceeds natural abundance levels. The crystal structure is discussed with respect to established limits of isomorphous substitution based on geometrical considerations and is compared to other iron‐rich micas. It is evidenced that the limitation of octahedral Fe II substitution in micas is not merely governed by the misfit of tetrahedral and octahedral sheets as indicated in the literature. The electronic conductivity of contacted single crystals (μS· cm –1 ) is comparable to the conductivity of Ferrous‐Tainiolite and is unfortunately not enhanced by the increased iron content. It is determined by the valence state of Fe rather than by the total Fe content. Abstract :