Comparison of the local and the average crystal structure of proton conducting lanthanum tungstate and the influence of molybdenum substitution

We report on the comparison of the local and average structure reported recently for proton conducting lanthanum tungstate, of general formula La28-xW4+xO54+V-delta(2-delta), and the impact of molybdenum-substitution on the crystal structure of the material. Partial replacement of W with 10 and 30 mol% Mo is investigated here, i.e. La-27(W1-xMox)(5)O-55.5 for x = 0.1 and 0.3. This study addresses the interpretation and the description of a disordered cation and anion sublattice in this material, which enables the understanding of the fundamental properties related to hydration, transport properties and degradation in lanthanum tungstate. The report shows that Mo-substituted lanthanum tungstate is a promising material as a dense oxide membrane for hydrogen separation at intermediate temperatures.