Structure of Nd5Mo3O16 + δ Single Crystals Doped with Tungsten

The structure of tungsten-doped Nd5Mo3O16 (+ delta) single crystals has been investigated by X-ray diffraction analysis, energy-dispersive X-ray spectroscopy (EDXS) microanalysis, and extended X-ray absorption fine-structure (EXAFS) spectroscopy. Tungsten atom, which partially replaces molybdenum atoms in the structure, is found to be located close (at a distance of 0.57 A) to the Mo atom site. The interstitial oxygen atom O3 shifts from the crystallographic site with coordinates (0.5, 0.5, 0) to the site with coordinates (0.43, 0.48, 0.04) and complements the tungsten coordination to octahedral. The decrease in the unit-cell parameter and conductivity with an increase in the tungsten concentration in the sample is shown to be related to the fact that the interstitial oxygen atom O3 (responsible for conductivity) is in the coordination environment of tungsten atom.