engleski

Model-Free Scaling of Conductivity Spectra: Insight Into Electrical Transport in Iron Phopshate-Based Glasees

Iron phosphate-based glasses (IPG) belong to a family of electronically conducting amorphous materials. A small polaron hopping conduction mechanism is observed owing to the presence of transition metal ions, e.g. iron, in more than one valence state. These materials are of great scientific interest due to their potential application as electrode materials for batteries, electronic circuit elements, electrical switching devices, etc. Here, we report on the impact of the additional glass-forming oxide on the polaronic transport in binary IPG glasses. The electrical transport properties and correlation to glass structure in B2O3–Fe2O3–P2O5 system are studied by Solid-State Impedance Spectroscopy (SSIS) in a wide frequency and temperature range.[1] Electrical transport in these glasses shows a strong dependence on the polaron number density determined by the overall Fe2O3 content and the fraction of Fe2+ ions. While the analysis of DC conductivity and its temperature dependence gives important information on the long-range transport of charge carriers in glasses, features of the frequency-dependent conductivity provide insights into the processes of their localized motions. The DC conductivity trend is found to be unimpaired to the amount of gradually added second glass-former, B2O3. However, a detailed study of the scaling properties of the conductivity spectra reveals that structural changes induced by its addition up to 17.7 mol %, notably impact frequency-dependent conductivity. In this respect, we apply two relatively simple yet very insightful scaling procedures, namely Summerfield and Sidebottom scaling. Obtained results provide new valuable information on the influence of B2O3, as a second glass-former, and resulting mixed glass network, on the formation of polarons and their dynamics.

electrical properties, glasses, impedance spectroscopy

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