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.