New double molybdate Na9Fe(MoO4)6: Synthesis, structure, properties

A new double molybdate Na9Fe(MoO4)6 was synthesized using solid state reactions and studied with X-ray powder diffraction, second harmonic generation (SHG) technique, differential scanning calorimetry, X-ray fluorescence analysis, Mössbauer and dielectric impedance spectroscopy. Single crystals of Na9Fe(MoO4)6 were obtained and its structure was solved (the space group R3¯, a=14.8264(2), c=19.2402(3)Å, V=3662.79(9)Å3, Z=6, R=0.0132). The structure is related to that of sodium ion conductor II-Na3Fe2(AsO4)3. The basic structure units are polyhedral clusters composed of central FeО6 octahedron sharing edges with three Na(1)О6 octahedra. The clusters share common vertices with bridging МоО4 tetrahedra to form an open 3D framework where the cavities are occupied by Na(2) and Na(3) atoms. The compound melts incongruently at 904.7±0.2K. Arrhenius type temperature dependence of electric conductivity σ has been registered in solid state (σ=6.8×10−2Sсm−1 at 800K), thus allowing considering Na9Fe(MoO4)6 as a new sodium ion conductor. A new double molybdate Na9Fe(MoO4)6 was synthesized and structurally characterized, its physicochemical properties were studied. [Display omitted] •A new compound Na9Fe(MoO4)6 was synthesized as ceramics and single crystals.•Na9Fe(MoO4)6 structure is related to that of sodium-ion conductor II-Na3Fe2(AsO4)3.•Physicochemical properties of the compound were studied.•Arrhenius plot for conductivity showed 6.8×10−2Scm−1 at 800K, Ea~0.8eV.•Thus, Na9Fe(MoO4)6 may be considered as a new sodium ion conductor.