New series of triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) with framework structures and mobile silver ion sublattices

• Triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg3In(MoO4)5 type were synthesized.
• Single crystals of AgMg3R(MoO4)5 (R=Cr, Fe) were grown and their crystal structures were determined.
• Disordering Ag+ ions and penetrable framework structures of AgMg3R(MoO4)5 (R=Cr, Fe) suggest 2D-character of silver-ion mobility.
• Measured ion-conductive properties of AgMg3Al(MoO4)5 are compatible with characteristics of the best ionic conductors of the NASICON type.

Triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg3In(MoO4)5 type were synthesized and single crystals of AgMg3R(MoO4)5 (R=Cr, Fe) were grown. In their structures, the MoO4 tetrahedra, pairs and trimers of edge-shared (Mg, R)O6 octahedra are connected by common vertices to form a 3D framework. Large framework cavities involve Ag+ cations disordered on three nearby positions with CN=3+1 or 4+1. Alternating (Mg, R)O6 octahedra and MoO4 tetrahedra in the framework form quadrangular windows penetrable for Ag+ at elevated temperatures. Above 653–673 K, the newly obtained molybdates demonstrate abrupt reduction of the activation energy to 0.4–0.6 eV. At 773 K, AgMg3Al(MoO4)5 shows electric conductivity 2.5·10−2 S/cm and Ea=0.39 eV compatible with characteristics of the best ionic conductors of the NASICON type.

Triple molybdates AgA3R(MoO4)5 (A=Mg, R=Cr, Fe; A=Mn, R=Al, Cr, Fe, Sc, In) of the NaMg3In(MoO4)5 type were synthesized, AgMg3R(MoO4)5 (R=Cr, Fe) were structurally characterized, ion-conductive properties of AgMg3Al(MoO4)5 were measured.Figure optionsDownload as PowerPoint slide