Site‐Preferences in the Mixed‐Valent Series FeMo _1−n V _n O ₄ : Controlling the Formation of the α‐Polymorph and the Charge Localization

The mixed-valent, solid solution series FeMo1−nVnO4 (0≤n≤0.3) was synthesized and characterized by x-ray diffraction, thermal analysis. Assignments of individual Fe-species stem from 57Fe-Mössbauer spectroscopy DFT-calculations the electric field gradients. incorporation smaller ions (FeIII, VV) represents an internal “chemical pressure” effect stabilizing low-temperature α-polymorph with increasing n. site-preference distribution vanadium on Mo-sites impacts α→β transition temperatures around 650 K, causes distinct differences in charge mobility this hole-doped semiconductor 225 K. We assign localization α-FeMo1−nVnO4 to enhanced electron-phonon coupling within a polaronic scenario.