Raman spectroscopy of Wadsley phases of vanadium oxide

We summarize the current knowledge on crystal structures, synthesis, applications, and Raman spectroscopy of Wadsley phases of vanadium oxide, including VO2 (B), V6O13, V4O9, V3O7, and V2O5. While these oxides have garnered significant attention for potential energy storage applications and have been studied for decades, there remains inconsistency in data regarding their characteristic Raman spectra. To address this, we synthesized a series of Wadsley phases by physical vapor deposition of amorphous vanadium oxide films and subsequent annealing in a controlled environment. X-ray diffraction studies confirmed the formation of VO2 (B), V6O13, V4O9, and V3O7. We meticulously measured the room-temperature Raman spectra of these phases, offering robust reference data for the easy identification of vanadium oxides in unknown samples. Finally, we studied low-temperature phase transitions in VO2 (B) and V6O13.