FullText URL J_Geophys_Res_122_158.pdf
Author Yoshino, Takashi| Zhang, Baohua| Rhymer, Brandon| Zhao, Chengcheng| Fei, Hongzhan|
Abstract Electrical conductivity of dry forsterite has been measured in muli-anvil apparatus to investigate the pressure dependence of ionic conduction in forsterite. The starting materials for the conductivity experiments were a synthetic forsterite single crystal and a sintered forsterite aggregate synthesized from oxide mixture. Electrical conductivities were measured at 3.5, 6.7, 9.6, 12.1, and 14.9 GPa between 1300 and 2100 K. In the measured temperature range, the conductivity of single crystal forsterite decreases in the order of [001], [010], and [100]. In all cases, the conductivity decreases with increasing pressure and then becomes nearly constant for [100] and [001] and slightly increases above 7 GPa for [010] orientations and a polycrystalline forsterite sample. Pressure dependence of forsterite conductivity was considered as a change of the dominant conduction mechanism composed of migration of both magnesium and oxygen vacancies in forsterite. The activation energy (ΔE) and activation volume (ΔV) for ionic conduction due to migration of Mg vacancy were 1.8–2.7 eV and 5–19 cm3/mol, respectively, and for that due to O vacancy were 2.2–3.1 eV and −1.1 to 0.3 cm3/mol, respectively. The olivine conductivity model combined with small polaron conduction suggests that the most part of the upper mantle is controlled by ionic conduction rather than small polaron conduction. The previously observed negative pressure dependence of the conductivity of olivine with low iron content (Fo90) can be explained by ionic conduction due to migration of Mg vacancies, which has a large positive activation volume.
Note This is an article published by Taylor & Francis Group
Published Date 2017-01-14
Publication Title Journal of Geophysical Research. Solid Earth
Volume volume122
Issue issue1
Publisher American Geophysical Union
Start Page 158
End Page 171
ISSN 2169-9313
NCID AA10819743
Content Type Journal Article
language 英語
OAI-PMH Set 岡山大学
Copyright Holders https://creativecommons.org/licenses/by-nc-nd/4.0/deed.ja
File Version publisher
DOI 10.1002/2016JB013555
Web of Sience KeyUT 000395658900009
Related Url https://doi.org/10.1002/2016JB013555