LAUSR

A new double molybdate Na 2 " role="presentation"> 2 2 _{2} Co 2 " role="presentation"> 2 2 _{2} (MoO 4 ) 3 " role="presentation"> 4 ) 3 4 ) 3 _{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 " role="presentation"> a a a = 5.272(2) Å, b " role="presentation"> b b b = 10.816(3) Å, and c " role="presentation"> c c c = 18.064(3) Å. The structure can be described as a three-dimensional framework with hexagonal tunnels in which the Na + " role="presentation"> + + ^{+} 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 × " role="presentation"> × × \times 10 − 6 " role="presentation"> − 6 − 6 ^{-6} S cm − 1 " role="presentation"> − 1 − 1 ^{-1} . The bond valence sum map model is used to simulate the cation migration pathways in the anionic framework.