β-Li(0.37)Na(0.63)Fe(MoO(4))(2)

The title compound, lithium/sodium iron(III) bis­[ortho­molyb­date(VI)], was obtained by a solid-state reaction. The main structure units are an FeO(6) octa­hedron, a distorted MoO(6) octa­hedron and an MoO(4) tetra­hedron sharing corners. The crystal structure is composed of infinite double MoFeO(11) chains along the b-axis direction linked by corner-sharing to MoO(4) tetra­hedra so as to form Fe(2)Mo(3)O(19) ribbons. The cohesion between ribbons via mixed Mo—O—Fe bridges leads to layers arranged parallel to the bc plane. Adjacent layers are linked by corners shared between MoO(4) tetra­hedra of one layer and FeO(6) octa­hedra of the other layer. The Na(+) and Li(+) ions partially occupy the same general position, with a site-occupancy ratio of 0.631 (9):0.369 (1). A comparison is made with AFe(MoO(4))(2) (A = Li, Na, K and Cs) structures.