Ab-initio structure determination of La34Mo8O75 using powder X-ray and neutron diffraction data

We report the synthesis, the structure determination, and the structure analysis of La34Mo8O75, which comprises 68 mol % La2O3 in the binary system La2O3–MoO3, in place of the previously reported compound La4MoO9, 66.7 mol % La2O3. This latter compound, which was reported in the literature without any structural information, is presented in this Article as part of the exploration of the La2O3–Nb2O5–MoO3 ternary phase diagram. Several diffraction techniques were used for the structural resolution of this compound such as powder X-ray and neutron diffraction as well as transmission electron microscopy in diffraction mode. La34Mo8O75 crystallizes in the monoclinic space group C2/m with the cell parameters: a = 17.070 A, b = 12.204 A, c = 9.742 A, β = 109.58°. The structure, related to fluorite, can be described as an anion-deficient fluorite with the global formula La34Mo8O75□9. The oxygen conduction of the compound was also investigated by means of complex impedance spectroscopy.