New molybdenum oxide Na1.92Mg2.04Mo3O12 has been synthesized by the solid state method. The title compound crystallizes in the triclinic system (space group P-1). The unit cell parameters are a？=？6.9660(7) ？, b？=？8.6352(8) ？, c？=？10.2501(8) ？, α？=？106.938(1)°, β？=？104.825(1)°, γ？=？103.206(1)°, V？=？538.72(9) ？3, and Z？=？2. The compound is isotypical to Ag2M2(MoO4)3 (M？=？Zn, Mg, Co, Mn). The structure can be described as a three-dimensional anionic mixed framework of MoO4 tetrahedra and pairs of Mg2O10 octahedra sharing common edges. The Na+ ions are disordered and located in the voids forming infinite channels running along the direction [100]. The electrical conductivity investigated from 693？K to 793？K by AC impedance spectroscopy is low ( ？S？cm？1 at 683？K). 1. Introduction The interest in the study of alkali molybdenum oxides is primarily in the unique structural and physical properties of some of these compounds which include high anisotropic transport properties [1, 2] and superconductivity and in their important application in the field of energy and electronics as described in several reviews [3, 4]. Some of complex molybdates crystallize in structure types which show significant ionic conductivity. For example, the structure of the Nasicon type molybdate [5] is of great interest because of high ionic conduction. For this reason the characterization of those oxides seems to be an important task. In our investigation, we synthesize new crystal of molybdenum oxide Na1.92Mg2.04Mo3O12. In our bibliographical search, we found the study of the phase diagram of the system Na2MoO4-MgMoO4 [6]; the system contains a single intermediate compound Na2Mg5(MoO4)6 [7]. The structural study reveals that the compound is isotypical to Na2Mg5(MoO4)6 [7], Ag2M2(MoO4)3 (M = Co, Mn, Mg, Zn) [8–10], and Na0.5Zn2.75(MoO4)3 [11]. (The cif file corresponding to the studied structure has been deposited in the database of Karlsruhe Number CSD. 426651 (http://www.fiz-karlsruhe.de/icsd.html)). 2. Experimental Details 2.1. Synthesis The compound is synthesized by the solid state method. A stoichiometric mixture of NaCO3 (Fluka, 71350), (NH4)2Mo4O13 (Fluka, 69858), and Mg(NO3)2·6H2O (Fluka, 63079), placed in a porcelain crucible, is slowly annealed in air at 350°C for 12 hours, in order to eliminate volatile products. The resulting mixtures were heated at 540°C for 7 days in air. Then, they were slowly cooled at 5°C/day to 490°C and finally, they were cooled at 50°C/day to room temperature. Single colorless crystals of double molybdates were grown by spontaneous crystallizations
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