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Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates
Zaineb Mighri1, Khalifa Souiwa1, Arpad Mihai Rostas2,3
1Laboratory of Physical Chemistry of Materials (LR01ES19), Faculty of Sciences of Monastir, University of Monastir, Avenue de l'Environnement, 5019 Monastir, Tunisia.
Abstract:
The phosphate KCoCr(PO4)2 and iron-substituted variants KCoCr1-Fe(PO4)2 (x = 0.25, 0.5, and 0.75) were synthesized by a solid-state reaction route, while a high substitution level of Fe was achieved. Their structures were refined using powder X-ray diffraction and indexed in a monoclinic system with a P21/n space group. A 3D framework with six-sided tunnels parallel to the [101] direction was formed in which the K atoms are located. Mössbauer spectroscopy confirms the exclusive presence of octahedral paramagnetic Fe3+ ions, with isomer shifts increasing slightly with x substitution. Electron paramagnetic resonance spectroscopy confirmed the presence of paramagnetic Cr3+ ions. The activation energy, determined by dielectric measurements, shows that the iron-containing samples present higher ionic activity. Relative to the electrochemical activity of K, these materials could be good candidates for positive and/or negative electrode materials for energy storage applications.
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