Physico-Chemical nanomaterials science

Pyroxenes as ion conductors
Skurikhina O.M.1,2, Achimovicova M.1, Senna M3
1 Institute of Geotechnics, Slovak Academy of Sciences, Watsonova 45, 04001, Košice, Slovakia. 
E-mail: olha.skurikhina@gmail.com
2 Faculty of Materials, Metallurgy and Recycling, Technical University of Košice, Letná 9, 04200, Košice, Slovakia
3 Department of Applied Chemistry, Faculty of Science and Technology, Keio University 3-14-1 Hiyoshi, Kohokuku, 223-8522, Yokohama, Japan.

Pyroxenes are the class of complex oxides with general formulas XYT2O6.  The reason behind the awakened interest in these oxides is their multiferroic behavior under low temperatures [1]. In the light of the newly discovered multiferroic properties, other characteristics of the pyroxenes have begun to be explored, such as electrochemical properties for potential use in Li-ion batteries [2-3]. Our goal was to establish the mechanism of ion dynamics of mobile X ions (Li+/Na+) in pyroxenes by impedance spectroscopy in the temperature range of 20-240 °C. Using the broadband impedance spectroscopy we investigated for the first time the mechanism of conductivity in orthorhombic pyroxenes - LiFeSi2O6, LiFeGe2O6, and NaFeGe2O6. 
Jonscher Power Law, Almond-West formalism, and Arrhenius equations were used to evaluate and fit experimental data. It was concluded that on the process of ion (Li+/Na+) motion (or ionic conductivity) influences only the features of crystal structure – the presence of YO6[FeO6] octahedral impedes the ion motion process. The entropy contribution and charge carrier concentration are not thermally activated.

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