Valence states and hybridization in vanadium oxide systems investigated by transmission electron-energy-loss spectroscopy

The electronic structure of vanadium oxides and (VO${)}_{2}$${\mathrm{P}}_{2}$${\mathrm{O}}_{7}$ is investigated by electron-energy-loss spectroscopy. The O K pre-edge in (VO${)}_{2}$${\mathrm{P}}_{2}$${\mathrm{O}}_{7}$ is substantially different from that of vanadium oxides, whereas the profiles of V ${\mathit{L}}_{2}$/${\mathit{L}}_{3}$ transition show no significant differences between these materials. We attribute the change of the O K pre-edge to the change of local symmetry of oxygen atoms in (VO${)}_{2}$${\mathrm{P}}_{2}$${\mathrm{O}}_{7}$ and the change of hybridization from pure d-p hybridization in vanadium oxide to mixed d-p-\ensuremath{\sigma} hybridization in (VO${)}_{2}$${\mathrm{P}}_{2}$${\mathrm{O}}_{7}$. It is also inferred that the V ${\mathit{L}}_{2}$/${\mathit{L}}_{3}$ transition ratio of (VO${)}_{2}$${\mathrm{P}}_{2}$${\mathrm{O}}_{7}$ is more like that of ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$.