Turkish Journal of Chemistry




A new double molybdate Na$_{2}$Co$_{2}$(MoO$_{4})_{3}$ was synthesized via solid-state reaction and characterized by single-crystal X-ray diffraction (XRD). This compound is a new member of the lyonsite structure type. It crystallized in the orthorhombic system, space group Pnma with cell parameters $a$ = 5.272(2) Å, $b$ = 10.816(3) Å, and $c$ = 18.064(3) Å. The structure can be described as a three-dimensional framework with hexagonal tunnels in which the Na$^{+}$ cations lie. The obtained structural model is supported by charge distribution analysis and bond valence sum validation tools. Fourier-transform infrared spectroscopy and scanning electron microscopy analyses were carried out. Ball milling was used to reduce the particle size of the synthesized powder. Dense ceramics with a relative density of 78% were obtained by sintering at 853 K. The conductivity of the title compound was studied for different relative densities. The ionic conductivity at 723 K with an activation energy of 1.2 eV was 3.24 $\times $ 10$^{-6}$ S cm$^{-1}$. The bond valence sum map model is used to simulate the cation migration pathways in the anionic framework.

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