Synthesis, crystal structure and electrophysical properties of triple molybdates containing silver, gallium and divalent metals

Abstract

A possibility of the triple molybdates formation with both NASICON-like and NaMg3In(MoO4)5 structures in the Ag2MoO4–AMoO4–Ga2(MoO4)3 (A = Mn, Co, Zn, Ni) systems was studied by powder X-ray diffraction analysis. It was established that NASICON-like phases Ag1−xA1−xGa1+x(MoO4)3 are not formed. The triple molybdates AgA3Ga (MoO4)5 (A = Mn, Co, Zn) isostructural to triclinic NaMg3In(MoO4)5 (sp. gr. P1, Z = 2) were synthesized and characterized. The structure of the obtained compounds was refined for AgZn3Ga(MoO4)5 according to the powder data by the Rietveld method. The structure consists of MoO4 tetrahedra, couples of edge-shared M(1)O6 octahedra, and trimers of edge-shared M(2)O6–, M(3)6–and M(4)O6 octahedra, which are linked by the common vertices to form a 3D framework. High-temperature conductivity measurements revealed that the conductivity of AgMn3Ga(MoO4)5 at 500 °C reaches 10–2 S / cm, which is close to one of the known NASICON-type ionic conductors.